main.js

'use strict';
console.clear();

const IS_MOBILE = window.innerWidth <= 640;
const IS_DESKTOP = window.innerWidth > 800;
const IS_HEADER = IS_DESKTOP && window.innerHeight < 300;

// Detect high end devices. This will be a moving target.
const IS_HIGH_END_DEVICE = (() => {
    const hwConcurrency = navigator.hardwareConcurrency;
    if (!hwConcurrency) {
        return false;
    }
    // Large screens indicates a full sized display, which is used on desktop or laptops and typically include hyper threading.
    // So a quad core desktop machine has 8 threads. We'll place a higher min threshold there.
    const minCount = window.innerWidth <= 1024 ? 4 : 8;
    return hwConcurrency >= minCount;
})();

// Prevent canvases from getting too large on hi-dpi displays.
// 8K - can restrict this if needed
const MAX_WIDTH = 7680;
const MAX_HEIGHT = 4320;
const GRAVITY = 0.9; // acceleration in px/s
let simSpeed = 1;

function getDefaultScaleFactor() {
    if (IS_MOBILE) return 0.9;
    if (IS_HEADER) return 0.75;
    return 1;
}

// Width/height values that take scale into account.
// Use these for drawing positions
let stageW, stageH;

// All quality globals will be overwritten and updated via `configDidUpdate`.
let quality = 1;
let isLowQuality = false;
let isNormalQuality = true;
let isHighQuality = false;

const QUALITY_LOW = 1;
const QUALITY_NORMAL = 2;
const QUALITY_HIGH = 3;

const SKY_LIGHT_NONE = 0;
const SKY_LIGHT_DIM = 1;
const SKY_LIGHT_NORMAL = 2;

const COLOR = {
    Red: '#ff0043',
	Green: '#14fc56',
	Blue: '#1e7fff',
	Purple: '#e60aff',
	Gold: '#ffbf36',
	White: '#ffffff'
}

// Special invisible color (not rendered, and therefore not in COLOR map)
const INVISIBLE = '_INVISIBLE_';

const PI_2 = Math.PI * 2;
const PI_HALF = Math.PI * 0.5;

// Stage.disableHighDPI = true;
const trailsStage = new Stage('trails-canvas');
const mainStage = new Stage('main-canvas');
const stages = [
    trailsStage,
    mainStage
];

// Fullscreen helpers, using Fscreen for prefixes.
function fullscreenEnabled() {
    return fscreen.fullscreenEnabled;
}

// NOTE: fullscreen state is synced to store, and the store should be the source
// of truth for whether the app is in fullscreen mode or not.
function isFullscreen() {
    return !!fscreen.fullscreenElement;
}

// Attempt to toggle fullscreen mode.
function toggleFullscreen() {
    if (fullscreenEnabled()) {
        if (isFullscreen()) {
            fscreen.exitFullscreen();
        } else {
            fscreen.requestFullscreen(document.documentElement);
        }
    }
}

// Sync fullscreen changes with store. An event listener is necessary because the user can
// toggle fullscreen mode directly through the browser, and we want to react to that.
fscreen.addEventListener('fullscreenchange', () => {
    store.setState({ fullscreen: isFullscreen() });
});


// Simple state container; the source of truth.
const store = {
    _listeners: new Set(),
    _dispatch(prevState) {
        this._listeners.forEach(listener => listener(this.state, prevState))
    },

    state: {
        // will be unpaused in init()
        paused: true,
        soundEnabled: true,
        menuOpen: false,
        openHelpTopic: null,
        fullscreen: isFullscreen(),
        // NOTE: config values used for <select>s must be strings, unless manually converting values to string
        // at render time, and parsing on change.
        config: {
            quality: String(IS_HIGH_END_DEVICE ? QUALITY_HIGH : QUALITY_NORMAL), // will be mirrored to a global variable named `quality` in `configDidUpdate`, for performance.
            shell: 'Random',
            size: IS_DESKTOP
                ? '3' // Desktop default
                : IS_HEADER
                    ? '1.2' // Profile header default (doesn't need to be an int)
                    : '2', // Mobile default
            autoLaunch: true,
            finale: false,
            skyLighting: SKY_LIGHT_NORMAL + '',
            hideControls: IS_HEADER,
            longExposure: false,
            scaleFactor: getDefaultScaleFactor()
        }
    },

    setState(nextState) {
        const prevState = this.state;
        this.state = Object.assign({}, this.state, nextState);
        this._dispatch(prevState);
        this.persist();
    },

    subscribe(listener) {
        this._listeners.add(listener);
        return () => this._listeners.remove(listener);
    },

    // Load / persist select state to localStorage
    // Mutates state because `store.load()` should only be called once immediately after store is created, before any subscriptions.
    load() {
        const serializedData = localStorage.getItem('cm_fireworks_data');
        if (serializedData) {
            const {
                schemaVersion,
                data
            } = JSON.parse(serializedData);

            const config = this.state.config;
            switch (schemaVersion) {
                case '1.1':
                    config.quality = data.quality;
                    config.size = data.size;
                    config.skyLighting = data.skyLighting;
                    break;
                case '1.2':
                    config.quality = data.quality;
                    config.size = data.size;
                    config.skyLighting = data.skyLighting;
                    config.scaleFactor = data.scaleFactor;
                    break;
                default:
                    throw new Error('version switch should be exhaustive');
            }
            console.log(`Loaded config (schema version ${schemaVersion})`);
        }
        // Deprecated data format. Checked with care (it's not namespaced).
        else if (localStorage.getItem('schemaVersion') === '1') {
            let size;
            // Attempt to parse data, ignoring if there is an error.
            try {
                const sizeRaw = localStorage.getItem('configSize');
                size = typeof sizeRaw === 'string' && JSON.parse(sizeRaw);
            }
            catch (e) {
                console.log('Recovered from error parsing saved config:');
                console.error(e);
                return;
            }
            // Only restore validated values
            const sizeInt = parseInt(size, 10);
            if (sizeInt >= 0 && sizeInt <= 4) {
                this.state.config.size = String(sizeInt);
            }
        }
    },

    persist() {
        const config = this.state.config;
        localStorage.setItem('cm_fireworks_data', JSON.stringify({
            schemaVersion: '1.2',
            data: {
                quality: config.quality,
                size: config.size,
                skyLighting: config.skyLighting,
                scaleFactor: config.scaleFactor
            }
        }));
    }
};

if (!IS_HEADER) {
    store.load();
}

// ACTIONS
// -------

function togglePause(toggle) {
    const paused = store.state.paused;
    let newValue;
    if (typeof toggle === 'boolean') {
        newValue = toggle;
    } else {
        newValue = !paused;
    }

    if (paused !== newValue) {
        store.setState({ paused: newValue });
    }
}

function toggleSound(toggle) {
    if (typeof toggle === 'boolean') {
        store.setState({ soundEnabled: toggle });
    } else {
        store.setState({ soundEnabled: !store.state.soundEnabled });
    }
}

function toggleMenu(toggle) {
    if (typeof toggle === 'boolean') {
        store.setState({ menuOpen: toggle });
    } else {
        store.setState({ menuOpen: !store.state.menuOpen });
    }
}

function updateConfig(nextConfig) {
    nextConfig = nextConfig || getConfigFromDOM();
    store.setState({
        config: Object.assign({}, store.state.config, nextConfig)
    });

    configDidUpdate();
}

// Map config to various properties & apply side effects
function configDidUpdate() {
    const config = store.state.config;

    quality = qualitySelector();
    isLowQuality = quality === QUALITY_LOW;
    isNormalQuality = quality === QUALITY_NORMAL;
    isHighQuality = quality === QUALITY_HIGH;
    
    if (skyLightingSelector() === SKY_LIGHT_NONE) {
        appNodes.canvasContainer.style.backgroundColor = '#000';
    }

    Spark.drawWidth = quality === QUALITY_HIGH ? 0.75 : 1;
}

// SELECTORS
// ---------

const isRunning = (state = store.state) => !state.paused && !state.menuOpen;
// Whether user has enabled sound.
const soundEnabledSelector = (state = store.state) => state.soundEnabled;
// Whether any sounds are allowed, taking into account multiple factors.
const canPlaySoundSelector = (state = store.state) => isRunning(state) && soundEnabledSelector(state);
// Convert quality to number.
const qualitySelector = () => +store.state.config.quality;
const shellNameSelector = () => store.state.config.shell;
// Convert shell size to number.
const shellSizeSelector = () => +store.state.config.size;
const finaleSelector = () => store.state.config.finale;
const skyLightingSelector = () => +store.state.config.skyLighting;
const scaleFactorSelector = () => store.state.config.scaleFactor;


// Help Content
const helpContent = {
    shellType: {
        header: 'Shell Type',
        body: 'The type of firework that will be launched. Select "Random" for a nice assortment!'
    },
    shellSize: {
        header: 'Shell Size',
        body: 'The size of the firework. Modeled after real firework shell sizes, larger shells have bigger bursts with more stars, and sometimes more complex effects. However, larger shells also require more processing power and may cause lag.'
    },
    quality: {
        header: 'Quality',
        boyd: 'Overall graphics quality. If the animation is not running smoothly, try lowering the quality. High quality greatly increases the amount of sparks rendered and may cause lag.'
    },
    skyLighting: {
        header: 'Sky Lighting',
        body: 'Illuminates the background as fireworks explode. If the background looks too bright on your screen, try setting it to "Dim" or "None".'
    },
    scaleFactor: {
        header: 'Scale',
        body: 'Allows scaling the size of all fireworks, essentially moving you closer or farther away. For larger shell sizes, it can be convenient to decrease the scale a bit, especially on phones or tablets.'
    },
    autoLaunch: {
        header: 'Auto Fire',
        body: 'Launches sequences of fireworks automatically. Sit back and enjoy the show, or disable to have full control.'
    },
    finaleMode: {
        header: 'Finale Mode',
        body: 'Launches intense bursts of fireworks. May cause lag. Requires "Auto Fire" to be enabled.'
    },
    hideControls: {
        header: 'Hide Controls',
        body: 'Hides the translucent controls along the top of the screen. Useful for screenshots, or just a more seamless experience. While hidden, you can still tap the top-right corner to re-open this menu.'
    },
    fullscreen: {
        header: 'Fullscreen',
        body: 'Toggles fullscreen mode.'
    },
    longExposure: {
        header: 'Open Shutter',
        body: 'Experimental effect that preserves long streaks of light, similar to leaving a camera shutter open.'
    }
};

const nodeKeyToHelpKey = {
	shellTypeLabel: 'shellType',
	shellSizeLabel: 'shellSize',
	qualityLabel: 'quality',
	skyLightingLabel: 'skyLighting',
	scaleFactorLabel: 'scaleFactor',
	autoLaunchLabel: 'autoLaunch',
	finaleModeLabel: 'finaleMode',
	hideControlsLabel: 'hideControls',
	fullscreenLabel: 'fullscreen',
	longExposureLabel: 'longExposure'
};

// Render app UI / keep in sync with state
const appNodes = {
    stageContainer: '.stage-container',
    canvasContainer: '.canvas-container',
    controls: '.controls',
    menu: '.menu',
    menuInnerWrap: '.menu__inner-wrap',
	pauseBtn: '.pause-btn',
	pauseBtnSVG: '.pause-btn use',
	soundBtn: '.sound-btn',
	soundBtnSVG: '.sound-btn use',
	shellType: '.shell-type',
	shellTypeLabel: '.shell-type-label',
	shellSize: '.shell-size',
	shellSizeLabel: '.shell-size-label',
	quality: '.quality-ui',
	qualityLabel: '.quality-ui-label',
	skyLighting: '.sky-lighting',
	skyLightingLabel: '.sky-lighting-label',
	scaleFactor: '.scaleFactor',
	scaleFactorLabel: '.scaleFactor-label',
	autoLaunch: '.auto-launch',
	autoLaunchLabel: '.auto-launch-label',
	finaleModeFormOption: '.form-option--finale-mode',
	finaleMode: '.finale-mode',
	finaleModeLabel: '.finale-mode-label',
	hideControls: '.hide-controls',
	hideControlsLabel: '.hide-controls-label',
	fullscreenFormOption: '.form-option--fullscreen',
	fullscreen: '.fullscreen',
	fullscreenLabel: '.fullscreen-label',
	longExposure: '.long-exposure',
    longExposureLabel: '.long-exposure-label',
    
    	// Help UI
	helpModal: '.help-modal',
	helpModalOverlay: '.help-modal__overlay',
	helpModalHeader: '.help-modal__header',
	helpModalBody: '.help-modal__body',
	helpModalCloseBtn: '.help-modal__close-btn'
};

// Converts appNodes selectors to DOM nodes
Object.keys(appNodes).forEach(key => {
    appNodes[key] = document.querySelector(appNodes[key]);
});

// Remove fullscreen control if not supported.
if (!fullscreenEnabled()) {
    appNodes.fullscreenFormOption.classList.add('remove');
}

// First render is called in init()
function renderApp(state) {
    const pauseBtnIcon = `#icon-${state.paused ? 'play' : 'pause'}`;
    const soundBtnIcon = `#icon-sound-${soundEnabledSelector() ? 'on' : 'off'}`;
    appNodes.pauseBtnSVG.setAttribute('href', pauseBtnIcon);
	appNodes.pauseBtnSVG.setAttribute('xlink:href', pauseBtnIcon);
	appNodes.soundBtnSVG.setAttribute('href', soundBtnIcon);
	appNodes.soundBtnSVG.setAttribute('xlink:href', soundBtnIcon);
	appNodes.controls.classList.toggle('hide', state.menuOpen || state.config.hideControls);
    appNodes.canvasContainer.classList.toggle('blur', state.menuOpen);
    appNodes.menu.classList.toggle('hide', !state.menuOpen);
    appNodes.finaleModeFormOption.style.opacity = state.config.autoLaunch ? 1 : 0.32;

    appNodes.quality.value = state.config.quality;
	appNodes.shellType.value = state.config.shell;
	appNodes.shellSize.value = state.config.size;
	appNodes.autoLaunch.checked = state.config.autoLaunch;
	appNodes.finaleMode.checked = state.config.finale;
	appNodes.skyLighting.value = state.config.skyLighting;
	appNodes.hideControls.checked = state.config.hideControls;
	appNodes.fullscreen.checked = state.fullscreen;
	appNodes.longExposure.checked = state.config.longExposure;
    appNodes.scaleFactor.value = state.config.scaleFactor.toFixed(2);
    
    appNodes.menuInnerWrap.style.opacity = state.openHelpTopic ? 0.12 : 1;
    appNodes.helpModal.classList.toggle('active', !!state.openHelpTopic);
    if (state.openHelpTopic) {
        const { header, body } = helpContent[state.openHelpTopic];
        appNodes.helpModalHeader.textContent = header;
        appNodes.helpModalBody.textContent = body;
    }
}

store.subscribe(renderApp);

// Perform side effects on state changes
function handleStateChange(state, prevState) {
    const canPlaySound = canPlaySoundSelector(state);
    const canPlaySoundPrev = canPlaySoundSelector(prevState);

    if (canPlaySound !== canPlaySoundPrev) {
        if (canPlaySound) {
            soundManager.resumeAll();
        } else {
            soundManager.pauseAll();
        }
    }
}

store.subscribe(handleStateChange);

function getConfigFromDOM() {
    return {
        quality: appNodes.quality.value,
		shell: appNodes.shellType.value,
		size: appNodes.shellSize.value,
		autoLaunch: appNodes.autoLaunch.checked,
		finale: appNodes.finaleMode.checked,
		skyLighting: appNodes.skyLighting.value,
		longExposure: appNodes.longExposure.checked,
		hideControls: appNodes.hideControls.checked,
		// Store value as number.
		scaleFactor: parseFloat(appNodes.scaleFactor.value)
    };
};

const updateConfigNoEvent = () => updateConfig();
appNodes.quality.addEventListener('input', updateConfigNoEvent);
appNodes.shellType.addEventListener('input', updateConfigNoEvent);
appNodes.shellSize.addEventListener('input', updateConfigNoEvent);
appNodes.autoLaunch.addEventListener('click', () => setTimeout(updateConfig, 0));
appNodes.finaleMode.addEventListener('click', () => setTimeout(updateConfig, 0));
appNodes.skyLighting.addEventListener('input', updateConfigNoEvent);
appNodes.longExposure.addEventListener('click', () => setTimeout(updateConfig, 0));
appNodes.hideControls.addEventListener('click', () => setTimeout(updateConfig, 0));
appNodes.fullscreen.addEventListener('click', () => setTimeout(toggleFullscreen, 0));
// Changing scaleFactor requires triggering resize handling code as well.
appNodes.scaleFactor.addEventListener('input', () => {
    updateConfig();
    handleResize();
});

Object.keys(nodeKeyToHelpKey).forEach(nodeKey => {
    const helpKey = nodeKeyToHelpKey[nodeKey];
    appNodes[nodeKey].addEventListener('click', () => {
        store.setState({ openHelpTopic: helpKey });
    });
});

appNodes.helpModalCloseBtn.addEventListener('click', () => {
	store.setState({ openHelpTopic: null });
});

appNodes.helpModalOverlay.addEventListener('click', () => {
	store.setState({ openHelpTopic: null });
});


// Constant derivations
const COLOR_NAMES = Object.keys(COLOR);
const COLOR_CODES = COLOR_NAMES.map(colorName => COLOR[colorName]);
// Invisible stars need an identifier, even though they won't be rendered - physics still apply.
const COLOR_CODES_W_INVIS = [...COLOR_CODES, INVISIBLE];
// Mpa of color codes to their index in the array. Useful for quickly determining if a color has already been update in a loop.
const COLOR_CODE_INDEXES = COLOR_CODES_W_INVIS.reduce((obj, code, i) => {
    obj[code] = i;
    return obj;
}, {});
// Tuples is a map of keys by colors codes (hex) with values of {r, g, b} tuples (still just objects).
const COLOR_TUPLES = {};
COLOR_CODES.forEach(hex => {
    COLOR_TUPLES[hex] = {
        r: parseInt(hex.substr(1, 2), 16),
        g: parseInt(hex.substr(3, 2), 16),
		b: parseInt(hex.substr(5, 2), 16),
    };
});

// Get a random color.
function randomColorSimple() {
    return COLOR_CODES[Math.random() * COLOR_CODES.length | 0];
}

// Get a random color, with some customization options available.
let lastColor;
function randomColor(options) {
    const notSame = options && options.notSame;
    const notColor = options && options.notColor;
    const  limitWhite = options && options.limitWhite;
    let color = randomColorSimple();

    // limit the amount of white chosen randomly
    if (limitWhite && color === COLOR.White && Math.random() < 0.6) {
        color = randomColorSimple();
    }

    if (notSame) {
        while (color === lastColor) {
            color = randomColorSimple();
        }
    }
    else if (notColor) {
        while (color === notColor) {
            color = randomColorSimple();
        }
    }

    lastColor = color;
    return color;
}

function whiteOrGold() {
    return Math.random() < 0.5 ? COLOR.Gold : COLOR.White;
}


// Shell helpers
function makePistilColor(shellColor) {
    return (shellColor === COLOR.White || shellColor === COLOR.Gold) ? randomColor({notColor: shellColor }) : whiteOrGold();
}

// Unique shell types
const crysanthemumShell = (size = 1) => {
    const glitter = Math.random() < 0.25;
    const singleColor = Math.random() < 0.72;
    const color = singleColor ? randomColor({ limitWhite: true }) : [randomColor(), randomColor({ notSame: true })];
    const pistil = singleColor && Math.random() < 0.42;
    const pistilColor = pistil && makePistilColor(color);
    const secondColor = singleColor && (Math.random() < 0.2 || color === COLOR.White) ? pistilColor || randomColor({ notColor: color, limitWhite: true }) : null;
    const streamers = !pistil && color !== COLOR.White && Math.random() < 0.42;
    let starDensity = glitter ? 1.1 : 1.25;
    if (isLowQuality) starDensity *= 0.8;
    if (isHighQuality) starDensity = 1.2;
    return {
        shellSize: size,
        spreadSize: 300 + size * 100,
        starLife: 900 + size * 200,
        starDensity,
        color,
        secondColor,
		glitter: glitter ? 'light' : '',
		glitterColor: whiteOrGold(),
		pistil,
		pistilColor,
		streamers
    };
};

const ghostShell = (size = 1) => {
    // Extend crysanthemum shell
    const shell = crysanthemumShell(size);
    // Ghost effect can be fast, so extend star life
    shell.starLife *= 1.5;
    // Ensure we always have a single color other than white
    let ghostColor = randomColor({ notColor: COLOR.White });
    // Always use streamers, and sometimes a pistil
    shell.streamers = true;
    const pistil = Math.random() < 0.42;
    const pistilColor = pistil && makePistilColor(ghostColor);
    // Ghost effect - transition from invisible to chosen color
    shell.color = INVISIBLE;
    shell.secondColor = ghostColor;
    // We don't want glitter to be spewed by invisible stars, and we don't currently
    // have a way to transition glitter state. So we'll disable it.
    shell.glitter = '';

    return shell;
};

const strobeShell = (size=1) => {
	const color = randomColor({ limitWhite: true });
	return {
		shellSize: size,
		spreadSize: 280 + size * 92,
		starLife: 1100 + size * 200,
		starLifeVariation: 0.40,
		starDensity: 1.1,
		color,
		glitter: 'light',
		glitterColor: COLOR.White,
		strobe: true,
		strobeColor: Math.random() < 0.5 ? COLOR.White : null,
		pistil: Math.random() < 0.5,
		pistilColor: makePistilColor(color)
	};
};

const palmShell = (size=1) => {
	const color = randomColor();
	const thick = Math.random() < 0.5;
	return {
		shellSize: size,
		color,
		spreadSize: 250 + size * 75,
		starDensity: thick ? 0.15 : 0.4,
		starLife: 1800 + size * 200,
		glitter: thick ? 'thick' : 'heavy'
	};
};

const ringShell = (size = 1) => {
	const color = randomColor();
	const pistil = Math.random() < 0.75;
	return {
		shellSize: size,
		ring: true,
		color,
		spreadSize: 300 + size * 100,
		starLife: 900 + size * 200,
		starCount: 2.2 * PI_2 * (size+1),
		pistil,
		pistilColor: makePistilColor(color),
		glitter: !pistil ? 'light' : '',
		glitterColor: color === COLOR.Gold ? COLOR.Gold : COLOR.White,
		streamers: Math.random() < 0.3
	};
};

const crossetteShell = (size = 1) => {
	const color = randomColor({ limitWhite: true });
	return {
		shellSize: size,
		spreadSize: 300 + size * 100,
		starLife: 750 + size * 160,
		starLifeVariation: 0.4,
		starDensity: 0.85,
		color,
		crossette: true,
		pistil: Math.random() < 0.5,
		pistilColor: makePistilColor(color)
	};
};

const floralShell = (size = 1) => ({
	shellSize: size,
	spreadSize: 300 + size * 120,
	starDensity: 0.12,
	starLife: 500 + size * 50,
	starLifeVariation: 0.5,
	color: Math.random() < 0.65 ? 'random' : (Math.random() < 0.15 ? randomColor() : [randomColor(), randomColor({ notSame: true })]),
	floral: true
});

const fallingLeavesShell = (size = 1) => ({
	shellSize: size,
	color: INVISIBLE,
	spreadSize: 300 + size * 120,
	starDensity: 0.12,
	starLife: 500 + size * 50,
	starLifeVariation: 0.5,
	glitter: 'medium',
	glitterColor: COLOR.Gold,
	fallingLeaves: true
});

const willowShell = (size = 1) => ({
	shellSize: size,
	spreadSize: 300 + size * 100,
	starDensity: 0.6,
	starLife: 3000 + size * 300,
	glitter: 'willow',
	glitterColor: COLOR.Gold,
	color: INVISIBLE
});

const crackleShell = (size = 1) => {
	// favor gold
	const color = Math.random() < 0.75 ? COLOR.Gold : randomColor();
	return {
		shellSize: size,
		spreadSize: 380 + size * 75,
		starDensity: isLowQuality ? 0.65 : 1,
		starLife: 600 + size * 100,
		starLifeVariation: 0.32,
		glitter: 'light',
		glitterColor: COLOR.Gold,
		color,
		crackle: true,
		pistil: Math.random() < 0.65,
		pistilColor: makePistilColor(color)
	};
};

const horsetailShell = (size = 1) => {
	const color = randomColor();
	return {
		shellSize: size,
		horsetail: true,
		color,
		spreadSize: 250 + size * 38,
		starDensity: 0.9,
		starLife: 2500 + size * 300,
		glitter: 'medium',
		glitterColor: Math.random() < 0.5 ? whiteOrGold() : color,
		// Add strobe effect to white horsetails, to make them more interesting
		strobe: color === COLOR.White
	};
};

function randomShellName() {
    return Math.random() < 0.5 ? 'Crysanthemum' : shellNames[(Math.random() * (shellNames.length - 1) + 1) | 0];
}

function randomShell(size) {
    // Special selection for header.
    if (IS_HEADER) return randomFastShell()(size);
    // Normal operation
    return shellTypes[randomShellName()](size);
}

function shellFromConfig(size) {
	return shellTypes[shellNameSelector()](size);
}

// Get a random shell, not including processing intensive variants
// NOTE: this is only random when "Random" shell is selected in config.
// Also, this does not create the shell, only return the factory function.
const fastShellBlacklist = ['Falling Leaves', 'Floral', 'Willow'];
function randomFastShell() {
    const isRandom = shellNameSelector() === 'Random';
    let shellName = isRandom ? randomShellName() : shellNameSelector();
    if (isRandom) {
        while (fastShellBlacklist.includes(shellName)) {
            shellName = randomShellName();
        }
    }
    return shellTypes[shellName]; 
}

const shellTypes = {
	'Random': randomShell,
	'Crackle': crackleShell,
	'Crossette': crossetteShell,
	'Crysanthemum': crysanthemumShell,
	'Falling Leaves': fallingLeavesShell,
	'Floral': floralShell,
	'Ghost': ghostShell,
	'Horse Tail': horsetailShell,
	'Palm': palmShell,
	'Ring': ringShell,
	'Strobe': strobeShell,
	'Willow': willowShell
};

const shellNames = Object.keys(shellTypes);

function init() {
    // Remove loading state
    document.querySelector('.loading-init').remove();
    appNodes.stageContainer.classList.remove('remove');

    // Populate dropdowns
    function setOptionsForSelect(node, options) {
        node.innerHTML = options.reduce((acc, opt) => acc += `<option value="${opt.value}">${opt.label}</option>`, '');
    }

    // shell type
    let options = '';
    shellNames.forEach(opt => options += `<option value="${opt}">${opt}</option>`);
    appNodes.shellType.innerHTML = options;
    // shell size
    options = '';
    ['3"', '4"', '6"', '8"', '12"', '16"'].forEach((opt, i) => options += `<option value="${i}">${opt}</option>`);
    appNodes.shellSize.innerHTML = options;

    setOptionsForSelect(appNodes.quality, [
		{ label: 'Low', value: QUALITY_LOW },
		{ label: 'Normal', value: QUALITY_NORMAL },
		{ label: 'High', value: QUALITY_HIGH }
	]);
	
	setOptionsForSelect(appNodes.skyLighting, [
		{ label: 'None', value: SKY_LIGHT_NONE },
		{ label: 'Dim', value: SKY_LIGHT_DIM },
		{ label: 'Normal', value: SKY_LIGHT_NORMAL }
    ]);
    
    // 0.9 is mobile default
    setOptionsForSelect(
		appNodes.scaleFactor,
		[0.5, 0.62, 0.75, 0.9, 1.0, 1.5, 2.0]
		.map(value => ({ value: value.toFixed(2), label: `${value*100}%` }))
    );
    
    // Begin simulation
    togglePause(false);

    // initial render
    renderApp(store.state);

    // Apply initial config
    configDidUpdate();
}


function fitShellPositionInBoundsH(position) {
    const edge = 0.18;
    return (1 - edge * 2) * position + edge;
}

function fitShellPositionInBoundsV(position) {
    return position * 0.75;
}

function getRandomShellPositionH() {
	return fitShellPositionInBoundsH(Math.random());
}
function getRandomShellPositionV() {
	return fitShellPositionInBoundsV(Math.random());
}

function getRandomShellSize() {
    const baseSize = shellSizeSelector();
    const maxVariance = Math.min(2.5, baseSize);
    const variance = Math.random() * maxVariance;
    const size = baseSize - variance;
    const height = maxVariance === 0 ? Math.random() : 1 - (variance / maxVariance);
    const centerOffset = Math.random() * (1 - height * 0.65) * 0.5;
    const x = Math.random() < 0.5 ? 0.5 - centerOffset : 0.5 + centerOffset;
    return {
        size,
        x: fitShellPositionInBoundsH(x),
        height: fitShellPositionInBoundsV(height)
    };
}


// Launches a shell from a user pointer event, based on state.config
function launchShellFromConfig(event) {
    const shell = new Shell(shellFromConfig(shellSizeSelector()));
    const w = mainStage.width;
    const h = mainStage.height;

    shell.launch(
        event ? event.x / w : getRandomShellPositionH(),
        event ? 1 - event.y / h : getRandomShellPositionV()
    );
}


// SEQUENCES
// ---------

function seqRandomShell() {
    const size = getRandomShellSize();
    const shell = new Shell(shellFromConfig(size.size));
    shell.launch(size.x, size.height);

    let extraDelay = shell.starLife;
    if (shell.fallingLeaves) {
        extraDelay = 4600;
    }

    return 900 + Math.random() * 600 + extraDelay;
}

function seqRandomFastShell() {
    const shellType = randomFastShell();
    const size = getRandomShellSize();
    const shell = new Shell(shellType(size.size));
    shell.launch(size.x, size.height);

    let extraDelay = shell.starLife;

    return 900 + Math.random() * 600 + extraDelay;
}

function seqTwoRandom() {
    const size1 = getRandomShellSize();
    const size2 = getRandomShellSize();
	const shell1 = new Shell(shellFromConfig(size1.size));
	const shell2 = new Shell(shellFromConfig(size2.size));
	const leftOffset = Math.random() * 0.2 - 0.1;
    const rightOffset = Math.random() * 0.2 - 0.1;
    shell1.launch(0.3 + leftOffset, size1.height);
    setTimeout(() => {
        shell2.launch(0.7 + rightOffset, size2.height);
    }, 100);

    let extraDelay = Math.max(shell1.starLife, shell2.starLife);
    if (shell1.fallingLeaves || shell2.fallingLeaves) {
        extraDelay = 4600;
    }

    return 900 + Math.random() * 600 + extraDelay;
}

function seqTriple() {
	const shellType = randomFastShell();
	const baseSize = shellSizeSelector();
	const smallSize = Math.max(0, baseSize - 1.25);
	
	const offset = Math.random() * 0.08 - 0.04;
	const shell1 = new Shell(shellType(baseSize));
	shell1.launch(0.5 + offset, 0.7);
	
	const leftDelay = 1000 + Math.random() * 400;
	const rightDelay = 1000 + Math.random() * 400;
	
	setTimeout(() => {
		const offset = Math.random() * 0.08 - 0.04;
		const shell2 = new Shell(shellType(smallSize));
		shell2.launch(0.2 + offset, 0.1);
	}, leftDelay);
	
	setTimeout(() => {
		const offset = Math.random() * 0.08 - 0.04;
		const shell3 = new Shell(shellType(smallSize));
		shell3.launch(0.8 + offset, 0.1);
	}, rightDelay);
	
	return 4000;
}

function seqPyramid() {
    const barrageCountHalf = IS_DESKTOP ? 7 : 4;
    const largeSize = shellSizeSelector();
    const smallSize = Math.max(0, largeSize - 3);
    const randomMainShell = Math.random() < 0.78 ? crysanthemumShell : ringShell;
    const randomSpecialShell = randomShell;

    function launchShell(x, useSpecial) {
        const isRandom = shellNameSelector() === 'Random';
        let shellType = isRandom
            ? useSpecial ? randomSpecialShell : randomMainShell
            : shellTypes[shellNameSelector()];
            const shell = new Shell(shellType(useSpecial ? largeSize : smallSize));
            const height = x <= 0.5 ? x / 0.5 : (1 - x) / 0.5;
            shell.launch(x, useSpecial ? 0.75 : height * 0.42);
    }

    let count = 0;
    let delay  =0;
    while (count <= barrageCountHalf) {
        if (count === barrageCountHalf) {
            setTimeout(() => {
                launchShell(0.5, true);
            }, delay);
        } else {
            const offset = count / barrageCountHalf * 0.5;
            const delayOffset = Math.random() * 30 + 30;
            setTimeout(() => {
                launchShell(offset, false);
            }, delay);
            setTimeout(() => {
				launchShell(1 - offset, false);
			}, delay + delayOffset);
        }

        count++;
        delay += 200;
    }

    return 3400 + barrageCountHalf * 250;
}

function seqSmallBarrage() {
    seqSmallBarrage.lastCalled = Date.now();
    const barrageCount = IS_DESKTOP ? 11 : 5;
    const specialIndex = IS_DESKTOP ? 3 : 1;
    const shellSize = Math.max(0, shellSizeSelector() - 2);
    const randomMainShell = Math.random() < 0.78 ? crysanthemumShell : ringShell;
    const randomSpecialShell = randomFastShell();

  // (cos(x*5π+0.5π)+1)/2 is a custom wave bounded by 0 and 1 used to set varying launch heights
  function launchShell(x, useSpecial) {
      const isRandom = shellNameSelector() === 'Random';
      let shellType = isRandom
        ? useSpecial ? randomSpecialShell : randomMainShell
        : shellTypes[shellNameSelector()];
        const shell = new Shell(shellType(shellSize));
        const height = (Math.cos(x * 5 * Math.PI + PI_HALF) + 1) / 2;
        shell.launch(x, height * 0.75);
  }

  let count = 0;
  let delay = 0;
  while (count < barrageCount) {
      if (count === 0) {
          launchShell(0.5, false);
          count += 1;
      } else {
          const offset = (count + 1) / barrageCount / 2;
          const delayOffset = Math.random() * 30 + 30;
          const useSpecial = count === specialIndex;
          setTimeout(() => {
            launchShell(0.5 + offset, useSpecial);
        }, delay);
        setTimeout(() => {
            launchShell(0.5 - offset, useSpecial);
        }, delay + delayOffset);
        count += 2;
      }
      delay += 200;
  }

  return 3400 + barrageCount * 120;
}
seqSmallBarrage.cooldown = 15000;
seqSmallBarrage.lastCalled = Date.now();


const sequences = [
    seqRandomShell,
	seqTwoRandom,
	seqTriple,
	seqPyramid,
	seqSmallBarrage
];


let isFirstSeq = true;
const finaleCount = 32;
let currentFinaleCount = 0;
function startSequence() {
    if (isFirstSeq) {
        isFirstSeq = false;
        if (IS_HEADER) {
            return seqTwoRandom();
        } else {
            const shell = new Shell(crysanthemumShell(shellSizeSelector()));
            shell.launch(0.5, 0.5);
            return 2400;
        }
    }

    if (finaleSelector()) {
        seqRandomFastShell();
        if (currentFinaleCount < finaleCount) {
            currentFinaleCount++;
            return 170;
        } else {
            currentFinaleCount = 0;
            return 6000;
        }
    }

    const rand = Math.random();

    if (rand < 0.08 && Date.now() - seqSmallBarrage.lastCalled > seqSmallBarrage.cooldown) {
        return seqSmallBarrage();
    }

    if (rand < 0.1) {
        return seqPyramid();
    }

    if (rand < 0.6 && !IS_HEADER) {
        return seqRandomShell();
    }
    else if (rand < 0.8) {
		return seqTwoRandom();
	}
	else if (rand < 1) {
		return seqTriple();
	}
}


let activePointerCount = 0;
let isUpdatingSpeed = false;

function handlePointerStart(event) {
    activePointerCount++;
    const btnSize = 50;

    if (event.y < btnSize) {
        if (event.x < btnSize) {
            togglePause();
            return;
        }
        if (event.x > mainStage.width / 2 - btnSize / 2 && event.x < mainStage.width / 2 + btnSize / 2) {
			toggleSound();
			return;
		}
		if (event.x > mainStage.width - btnSize) {
			toggleMenu();
			return;
		}
    }

    if (!isRunning()) return;

    if (updateSpeedFromEvent(event)) {
        isUpdatingSpeed = true;
    }
    else if (event.onCanvas) {
        launchShellFromConfig(event);
    }
}

function handlePointerEnd(event) {
    activePointerCount--;
    isUpdatingSpeed = false;
}

function handlePointerMove(event) {
    if (!isRunning()) return;

    if (isUpdatingSpeed) {
        updateSpeedFromEvent(event);
    }
}

function handleKeydown(event) {
    	// P
	if (event.keyCode === 80) {
		togglePause();
	}
	// O
	else if (event.keyCode === 79) {
		toggleMenu();
	}
	// Esc
	else if (event.keyCode === 27) {
		toggleMenu(false);
	}
}

mainStage.addEventListener('pointerstart', handlePointerStart);
mainStage.addEventListener('pointerend', handlePointerEnd);
mainStage.addEventListener('pointermove', handlePointerMove);
window.addEventListener('keydown', handleKeydown);


// Account for window resize and custom scale changes.
function handleResize() {
    const w = window.innerWidth;
    const h = window.innerHeight;
    // Try to adopt screen size, heeding maximum sizes specified
    const containerW = Math.min(w, MAX_WIDTH);
    // On small screens, use full device height
    const containerH = w <= 420 ? h : Math.min(h, MAX_HEIGHT);
	appNodes.stageContainer.style.width = containerW + 'px';
    appNodes.stageContainer.style.height = containerH + 'px';
    stages.forEach(stage => stage.resize(containerW, containerH));
    // Account for scale
    const scaleFactor = scaleFactorSelector();
    stageW = containerW / scaleFactor;
	stageH = containerH / scaleFactor;
}

// Compute initial dimensions
handleResize();

window.addEventListener('resize', handleResize);


// Dynamic globals
let currentFrame = 0;
let speedBarOpacity = 0;
let autoLaunchTime = 0;

function updateSpeedFromEvent(event) {
    if (isUpdatingSpeed || event.y >= mainStage.height - 44) {
        // On phones it's hard to hit the edge pixels in order to set speed at 0 or 1, so some padding is provided to make that easier.
        const edge = 16;
        const newSpeed = (event.x - edge) / (mainStage.width - edge * 2);
        simSpeed = Math.min(Math.max(newSpeed, 0), 1);
        // show speed bar after an update
        speedBarOpacity = 1;
        // If we updated the speed, return true
        return true;
    }
	// Return false if the speed wasn't updated
	return false;
}


// Extracted function to keep `update()` optimized
function updateGlobals(timeStep, lag) {
    currentFrame++;

    // Always try to fade out speed bar
    if (!isUpdatingSpeed) {
        speedBarOpacity -= lag / 30; // half a second
        if (speedBarOpacity < 0) {
            speedBarOpacity = 0;
        }
    }

    // auto launch shells
    if (store.state.config.autoLaunch) {
        autoLaunchTime -= timeStep;
        if (autoLaunchTime <= 0) {
            autoLaunchTime = startSequence() * 1.25;
        }
    }
}


function update(frameTime, lag) {
    if (!isRunning()) return;

    const width = stageW;
    const height = stageH;
    const timeStep = frameTime * simSpeed;
    const speed = simSpeed * lag;

    updateGlobals(timeStep, lag);

    const starDrag = 1 - (1 - Star.airDrag) * speed;
    const starDragHeavy = 1 - (1 - Star.airDragHeavy) * speed;
    const sparkDrag = 1 - (1 - Spark.airDrag) * speed;
    const gAcc = timeStep / 1000 * GRAVITY;
    COLOR_CODES_W_INVIS.forEach(color => {
        // Stars
        const stars = Star.active[color];
        for (let i = stars.length - 1; i >= 0; i = i - 1) {
            const star = stars[i];
            // Only update each star once per frame. Since color can change, it's possible a star could update twice without this, leading to a "jump".
            if (star.updateFrame === currentFrame) {
                continue;
            }
            star.updateFrame = currentFrame;

            star.life -= timeStep;
            if (star.life <= 0) {
                stars.splice(i, 1);
                Star.returnInstance(star);
            } else {
                const burnRate = Math.pow(star.life / star.fullLife, 0.5);
                const burnRateInverse = 1 - burnRate;

                star.prevX = star.x;
                star.prevY = star.y;
                star.x += star.speedX * speed;
                star.y += star.speedY * speed;
                // Apply air drag if star isn't "heavy". The heavy property is used for the shell comets.
                if (!star.heavy) {
                    star.speedX *= starDrag;
                    star.speedY *= starDrag;
                } else {
                    star.speedX *= starDragHeavy;
					star.speedY *= starDragHeavy;
                }
                star.speedY += gAcc;

                if (star.spinRadius) {
                    star.spinAngle += star.spinSpeed * speed;
                    star.x += Math.sin(star.spinAngle) * star.spinRadius * speed;
                    star.y += Math.cos(star.spinAngle) * star.spinRadius * speed;
                }

                if (star.sparkFreq) {
                    star.sparkTimer -= timeStep;
                    while (star.sparkTimer < 0) {
                        star.sparkTimer += star.sparkFreq * 0.75 + star.sparkFreq * burnRateInverse * 4;
                        Spark.add(
                            star.x,
                            star.y,
                            star.sparkColor,
                            Math.random() * PI_2,
                            Math.random() * star.sparkSpeed * burnRate,
                            star.sparkLife * 0.8 + Math.random() * star.sparkLifeVariation * star.sparkLife
                        );
                    }
                }

                // Handle star transitions
                if (star.life < star.transitionTime) {
                    if (star.secondColor && !star.colorChanged) {
                        star.colorChanged = true;
                        star.color = star.secondColor;
                        stars.splice(i, 1);
                        Star.active[star.secondColor].push(star);
                        if (star.secondColor === INVISIBLE) {
                            star.sparkFreq = 0;
                        }
                    }

                    if (star.strobe) {
                        // Strobes int he following pattern: on:off:off:on:off:off in increments of `strobeFreq` ms.
                        star.visible = Math.floor(star.life / star.strobeFreq) % 3 === 0;
                    }
                }
            }
        }

        // Sparks
        const sparks = Spark.active[color];
        for (let i = sparks.length - 1; i >= 0; i = i - 1) {
            const spark = sparks[i];
            spark.life -= timeStep;
            if (spark.life <= 0) {
                sparks.splice(i, 1);
                Spark.returnInstance(spark);
            } else {
                spark.prevX = spark.x;
				spark.prevY = spark.y;
				spark.x += spark.speedX * speed;
				spark.y += spark.speedY * speed;
				spark.speedX *= sparkDrag;
				spark.speedY *= sparkDrag;
				spark.speedY += gAcc;
            }
        }
    });

    render(speed);
}

function render(speed) {
    const { dpr } = mainStage;
    const width = stageW;
    const height = stageH;
    const trailsCtx = trailsStage.ctx;
    const mainCtx = mainStage.ctx;

    if (skyLightingSelector() !== SKY_LIGHT_NONE) {
        colorSky(speed);
    }

    // Account for high DPI screens, and custom scale factor.
    const scaleFactor = scaleFactorSelector();
    trailsCtx.scale(dpr * scaleFactor, dpr * scaleFactor);
    mainCtx.scale(dpr * scaleFactor, dpr * scaleFactor);

    trailsCtx.globalCompositeOperation = 'source-over';
    trailsCtx.fillStyle = `rgba(0, 0, 0, ${store.state.config.longExposure ? 0.0025 : 0.175 * speed})`;
	trailsCtx.fillRect(0, 0, width, height);
	
    mainCtx.clearRect(0, 0, width, height);
    
    // Draw queued burst flashes
    // These must also be drawn using source-over due to Safari. Seems rendering the gradients using lighten draw large block boxes instead.
    // Thankfully, these burst flasges looks pretty much the same either way.
    while (BurstFlash.active.length) {
        const bf = BurstFlash.active.pop();

        const burstGradient = trailsCtx.createRadialGradient(bf.x, bf.y, 0, bf.x, bf.y, bf.radius);
		burstGradient.addColorStop(0.024, 'rgba(255, 255, 255, 1)');
		burstGradient.addColorStop(0.125, 'rgba(255, 160, 20, 0.2)');
		burstGradient.addColorStop(0.32, 'rgba(255, 140, 20, 0.11)');
		burstGradient.addColorStop(1, 'rgba(255, 120, 20, 0)');
		trailsCtx.fillStyle = burstGradient;
		trailsCtx.fillRect(bf.x - bf.radius, bf.y - bf.radius, bf.radius * 2, bf.radius * 2);
		
		BurstFlash.returnInstance(bf);
    }

    // Remaining drawing on trails canvas will use 'lighten' blend mode
    trailsCtx.globalCompositeOperation = 'lighten';

    // Draw stars
    trailsCtx.lineWidth = Star.drawWidth;
    trailsCtx.lineCap = isLowQuality ? 'square' : 'round';
    mainCtx.strokeStyle = '#fff';
    mainCtx.lineWidth = 1;
    mainCtx.beginPath();
    COLOR_CODES.forEach(color => {
        const stars = Star.active[color];
        trailsCtx.strokeStyle = color;
        trailsCtx.beginPath();
        stars.forEach(star => {
            if (star.visible) {
                trailsCtx.moveTo(star.x, star.y);
                trailsCtx.lineTo(star.prevX, star.prevY);
                mainCtx.moveTo(star.x, star.y);
                mainCtx.lineTo(star.x - star.speedX * 1.6, star.y - star.speedY * 1.6);
            }
        });
        trailsCtx.stroke();
    });
    mainCtx.stroke();

    // Draw sparks
    trailsCtx.lineWidth = Spark.drawWidth;
    trailsCtx.lineCap = 'butt';
    COLOR_CODES.forEach(color => {
		const sparks = Spark.active[color];
		trailsCtx.strokeStyle = color;
		trailsCtx.beginPath();
		sparks.forEach(spark => {
			trailsCtx.moveTo(spark.x, spark.y);
			trailsCtx.lineTo(spark.prevX, spark.prevY);
		});
		trailsCtx.stroke();
    });
    
    // Render speed bar if visible
    if (speedBarOpacity) {
        const speedBarHeight = 6;
        mainCtx.globalAlpha = speedBarOpacity;
        mainCtx.fillStyle = COLOR.Blue;
        mainCtx.fillRect(0, height - speedBarHeight, width * simSpeed, speedBarHeight);
        mainCtx.globalAlpha = 1;
    }

    trailsCtx.setTransform(1, 0, 0, 1, 0, 0);
	mainCtx.setTransform(1, 0, 0, 1, 0, 0);
}


// Draw colored overlay based on combined brightness of stars (light up the sky!)
// NOTE: this is applied to the canvas container's background-color, so it's behind the particles
const currentSkyColor = { r: 0, g: 0, b: 0 };
const targetSkyColor = { r: 0, g: 0, b: 0 };
function colorSky(speed) {
	// The maximum r, g, or b value that will be used (255 would represent no maximum)
	const maxSkySaturation = skyLightingSelector() * 15;
	// How many stars are required in total to reach maximum sky brightness
	const maxStarCount = 500;
	let totalStarCount = 0;
	// Initialize sky as black
	targetSkyColor.r = 0;
	targetSkyColor.g = 0;
	targetSkyColor.b = 0;
	// Add each known color to sky, multiplied by particle count of that color. This will put RGB values wildly out of bounds, but we'll scale them back later.
	// Also add up total star count.
	COLOR_CODES.forEach(color => {
		const tuple = COLOR_TUPLES[color];
		const count =  Star.active[color].length;
		totalStarCount += count;
		targetSkyColor.r += tuple.r * count;
		targetSkyColor.g += tuple.g * count;
		targetSkyColor.b += tuple.b * count;
	});
	
	// Clamp intensity at 1.0, and map to a custom non-linear curve. This allows few stars to perceivably light up the sky, while more stars continue to increase the brightness but at a lesser rate. This is more inline with humans' non-linear brightness perception.
	const intensity = Math.pow(Math.min(1, totalStarCount / maxStarCount), 0.3);
	// Figure out which color component has the highest value, so we can scale them without affecting the ratios.
	// Prevent 0 from being used, so we don't divide by zero in the next step.
	const maxColorComponent = Math.max(1, targetSkyColor.r, targetSkyColor.g, targetSkyColor.b);
	// Scale all color components to a max of `maxSkySaturation`, and apply intensity.
	targetSkyColor.r = targetSkyColor.r / maxColorComponent * maxSkySaturation * intensity;
	targetSkyColor.g = targetSkyColor.g / maxColorComponent * maxSkySaturation * intensity;
	targetSkyColor.b = targetSkyColor.b / maxColorComponent * maxSkySaturation * intensity;
	
	// Animate changes to color to smooth out transitions.
	const colorChange = 10;
	currentSkyColor.r += (targetSkyColor.r - currentSkyColor.r) / colorChange * speed;
	currentSkyColor.g += (targetSkyColor.g - currentSkyColor.g) / colorChange * speed;
	currentSkyColor.b += (targetSkyColor.b - currentSkyColor.b) / colorChange * speed;
	
	appNodes.canvasContainer.style.backgroundColor = `rgb(${currentSkyColor.r | 0}, ${currentSkyColor.g | 0}, ${currentSkyColor.b | 0})`;
}

mainStage.addEventListener('ticker', update);


// Helper used to semi-randomly spread particles over an arc
// Values are flexible - `start` and `arcLength` can be negative, and `randomness` is simply a multiplier for random additon.
function createParticleArc(start, arcLength, count, randomness, particleFactory) {
    const angleDelta = arcLength / count;
    // Sometimes there is an extra particle at the end, too close to the start. Subtracting half the angleDelta ensures that is skipped.
    // Would be nice to fix this a better way.
    const end = start + arcLength - (angleDelta * 0.5);

    if (end > start) {
        // Optimization: `angle=angle+angleDelta` vs. angle+=angleDelta
        // V8 deoptimizes with let compound assignment
        for (let angle = start; angle < end; angle = angle + angleDelta) {
            particleFactory(angle + Math.random() * angleDelta * randomness);
        }
    } else {
        for (let angle = start; angle > end; angle = angle + angleDelta) {
            particleFactory(angle + Math.random() * angleDelta * randomness);
        }
    }
}

/**
 * Helper used to create a spherical burst of particles.
 *
 * @param  {Number} count               The desired number of stars/particles. This value is a suggestion, and the
 *                                      created burst may have more particles. The current algorithm can't perfectly
 *                                      distribute a specific number of points evenly on a sphere's surface.
 * @param  {Function} particleFactory   Called once per star/particle generated. Passed two arguments:
 *                                        `angle`: The direction of the star/particle.
 *                                        `speed`: A multipler for the particle speed, from 0.0 to 1.0.
 * @param  {Number} startAngle=0        For segmented bursts, you can generate only a partial arc of particles. This
 *                                      allows setting the starting arc angle (radians).
 * @param  {Number} arcLength=TAU       The length of the arc (radians). Defaults to a full circle.
 *
 * @return {void}                       Returns nothing; it's up to `particleFactory` to use the given data.
 */
function createBurst(count, particleFactory, startAngle = 0, arcLength = PI_2) {
    // Assuming sphere with surface area of `count`, calculate various
    // properties of said sphere (unit is stars).
    // Radius
    const R = 0.5 * Math.sqrt(count / Math.PI);
    // Circumference
    const C = 2 * R * Math.PI;
    // Half Circumference
    const C_HALF = C / 2;

    // Make a series of rings, sizing them as if they were spaced evenly
    // along the curved surface of a sphere.
    for (let i = 0; i <= C_HALF; i++) {
        const ringAngle = i / C_HALF * PI_HALF;
        const ringSize = Math.cos(ringAngle);
        const partsPerFullRing = C * ringSize;
        const partsPerArc = partsPerFullRing * (arcLength / PI_2);

        const angleInc = PI_2 / partsPerFullRing;
        const angleOffset = Math.random() * angleInc + startAngle;
        // Each particles needs a bit of randomness to improve appearance.
        const maxRandomAngleOffset = angleInc * 0.33;

        for (let i = 0; i < partsPerArc; i++) {
            const randomAngleOffset = Math.random() * maxRandomAngleOffset;
            let angle = angleInc * i + angleOffset + randomAngleOffset;
            particleFactory(angle, ringSize);    
        }
    }
}


// Various star effects.
// These are designed to be attached to a star's `onDeath` event.

// Crossette breaks star into four same-color pieces which branch in a cross-like shape.
function crossetteEffect(star) {
    const startAngle = Math.random() * PI_HALF;
    createParticleArc(startAngle, PI_2, 4, 0.5, (angle) => {
        Star.add(
            star.x,
            star.y,
            star.color,
            angle,
            Math.random() * 0.6 + 0.75,
            600
        );
    });
}

// Flow is like a mini shell
function floralEffect(star) {
    const count = 12 + 6 * quality;
    createBurst(count, (angle, speedMult) => {
        Star.add(
			star.x,
			star.y,
			star.color,
			angle,
			speedMult * 2.4,
			1000 + Math.random() * 300,
			star.speedX,
			star.speedY
		);
    });
    // Queue burst flash render
    BurstFlash.add(star.x, star.y, 46);
    soundManager.playSound('burstSmall');
}

// Floral burst with willow stars
function fallingLeavesEffect(star) {
	createBurst(7, (angle, speedMult) => {
		const newStar = Star.add(
			star.x,
			star.y,
			INVISIBLE,
			angle,
			speedMult * 2.4,
			2400 + Math.random() * 600,
			star.speedX,
			star.speedY
		);
		
		newStar.sparkColor = COLOR.Gold;
		newStar.sparkFreq = 144 / quality;
		newStar.sparkSpeed = 0.28;
		newStar.sparkLife = 750;
		newStar.sparkLifeVariation = 3.2;
	});
	// Queue burst flash render
	BurstFlash.add(star.x, star.y, 46);
	soundManager.playSound('burstSmall');
}

// Crackle pops into a small cloud of golden sparks.
function crackleEffect(star) {
	const count = isHighQuality ? 32 : 16;
	createParticleArc(0, PI_2, count, 1.8, (angle) => {
		Spark.add(
			star.x,
			star.y,
			COLOR.Gold,
			angle,
			// apply near cubic falloff to speed (places more particles towards outside)
			Math.pow(Math.random(), 0.45) * 2.4,
			300 + Math.random() * 200
		);
	});
}


/**
 * Shell can be constructed with options:
 *
 * spreadSize:      Size of the burst.
 * starCount: Number of stars to create. This is optional, and will be set to a reasonable quantity for size if omitted.
 * starLife:
 * starLifeVariation:
 * color:
 * glitterColor:
 * glitter: One of: 'light', 'medium', 'heavy', 'streamer', 'willow'
 * pistil:
 * pistilColor:
 * streamers:
 * crossette:
 * floral:
 * crackle:
 */
class Shell  {
    constructor(options) {
        Object.assign(this, options);
        this.starLifeVariation = options.starLifeVariation || 0.125;
        this.color = options.color || randomColor();
        this.glitterColor = options.glitterColor || this.color;

        // Set default starCount if needed, will be based on shell size and scale exponentially, like a sphere's surface area.
        if (!this.starCount) {
            const density = options.starDensity || 1;
            const scaledSize = this.spreadSize / 54;
            this.starCount = Math.max(6, scaledSize * scaledSize * density);
        }
    }

    launch(position, launchHeight) {
        const width = stageW;
        const height = stageH;
        // Distance from sides of screen to keep shells.
        const hpad = 60;
        // Distance from top of screen to keep shell bursts.
        const vpad = 50;
      	// Minimum burst height, as a percentage of stage height
		const minHeightPercent = 0.45;
		// Minimum burst height in px
        const minHeight = height - height * minHeightPercent;
        
        const launchX = position * (width - hpad * 2) + hpad;
		const launchY = height;
        const burstY = minHeight - (launchHeight * (minHeight - vpad));
        
        const launchDistance = launchY - burstY;
        // Using a custom power curve to approximate Vi needed to reach launchDistance under gravity and air drag.
        // Magic numbers came from testing.
        const launchVelocity = Math.pow(launchDistance * 0.04, 0.64);

        const comet = this.comet = Star.add(
            launchX,
            launchY,
            typeof this.color === 'string' && this.color !== 'random' ? this.color : COLOR.White,
			Math.PI,
			launchVelocity * (this.horsetail ? 1.2 : 1),
			// Hang time is derived linearly from Vi; exact number came from testing
			launchVelocity * (this.horsetail ? 100 : 400)
        );

        // making comet "heavy" limits air drag
        comet.heavy = true;
        // comet spark trail
        comet.spinRadius = MyMath.random(0.32, 0.85);
        comet.sparkFreq = 32 / quality;
        if (isHighQuality) comet.sparkFreq = 8;
        comet.sparkLife = 320;
        comet.sparkLifeVariation = 3;
        if (this.glitter === 'willow' || this.fallingLeaves) {
            comet.sparkFreq = 20 / quality;
            comet.sparkSpeed = 0.5;
            comet.sparkLife = 500;
        }
        if (this.color === INVISIBLE) {
            comet.sparkColor = COLOR.Gold;
        }

        // Randomly make comet "burn out" a bit early.
		// This is disabled for horsetail shells, due to their very short airtime.
		if (Math.random() > 0.4 && !this.horsetail) {
			comet.secondColor = INVISIBLE;
			comet.transitionTime = Math.pow(Math.random(), 1.5) * 700 + 500;
		}
		
		comet.onDeath = comet => this.burst(comet.x, comet.y);
		
		soundManager.playSound('lift');
    }

    burst(x, y) {
        // Set burst speed so overall burst grows to set size. This specific formula was derived from testing, and is affected by simulated air drag.
        const speed = this.spreadSize / 96;
        
        let color, onDeath, sparkFreq, sparkSpeed, sparkLife;
        let sparkLifeVariation = 0.25;
        	// Some death effects, like crackle, play a sound, but should only be played once.
        let playedDeathSound = false;
        
        if (this.crossette) onDeath = (star) => {
            if (!playedDeathSound) {
                soundManager.playSound('crackleSmall');
                playedDeathSound = true;
            }
            crossetteEffect(star);
        }
        if (this.crackle) onDeath = (star) => {
			if (!playedDeathSound) {
				soundManager.playSound('crackle');
				playedDeathSound = true;
			}
			crackleEffect(star);
		}
		if (this.floral) onDeath = floralEffect;
        if (this.fallingLeaves) onDeath = fallingLeavesEffect;
        
        if (this.glitter === 'light') {
			sparkFreq = 400;
			sparkSpeed = 0.3;
			sparkLife = 300;
			sparkLifeVariation = 2;
		}
		else if (this.glitter === 'medium') {
			sparkFreq = 200;
			sparkSpeed = 0.44;
			sparkLife = 700;
			sparkLifeVariation = 2;
		}
		else if (this.glitter === 'heavy') {
			sparkFreq = 80;
			sparkSpeed = 0.8;
			sparkLife = 1400;
			sparkLifeVariation = 2;
		}
		else if (this.glitter === 'thick') {
			sparkFreq = 16;
			sparkSpeed = isHighQuality ? 1.65 : 1.5;
			sparkLife = 1400;
			sparkLifeVariation = 3;
		}
		else if (this.glitter === 'streamer') {
			sparkFreq = 32;
			sparkSpeed = 1.05;
			sparkLife = 620;
			sparkLifeVariation = 2;
		}
		else if (this.glitter === 'willow') {
			sparkFreq = 120;
			sparkSpeed = 0.34;
			sparkLife = 1400;
			sparkLifeVariation = 3.8;
        }
        
        // Apply quality to spark count
        sparkFreq = sparkFreq / quality;

        // Star factory for primary burst, pistils, and streamers.
        let firstStar = true;
        const starFactory = (angle, speedMult) => {
            // For non-horsetail shells, compute an initial vertical speed to add to star burst.
			// The magic number comes from testing what looks best. The ideal is that all shell
			// bursts appear visually centered for the majority of the star life (excl. willows etc.)
            const standardInitialSpeed = this.spreadSize / 1800;
            
            const star = Star.add(
				x,
				y,
				color || randomColor(),
				angle,
				speedMult * speed,
				// add minor variation to star life
				this.starLife + Math.random() * this.starLife * this.starLifeVariation,
				this.horsetail ? this.comet && this.comet.speedX : 0,
				this.horsetail ? this.comet && this.comet.speedY : -standardInitialSpeed
			);
	
			if (this.secondColor) {
				star.transitionTime = this.starLife * (Math.random() * 0.05 + 0.32);
				star.secondColor = this.secondColor;
			}

			if (this.strobe) {
				star.transitionTime = this.starLife * (Math.random() * 0.08 + 0.46);
				star.strobe = true;
				// How many milliseconds between switch of strobe state "tick". Note that the strobe pattern
				// is on:off:off, so this is the "on" duration, while the "off" duration is twice as long.
				star.strobeFreq = Math.random() * 20 + 40;
				if (this.strobeColor) {
					star.secondColor = this.strobeColor;
				}
            }
            
            star.onDeath = onDeath;

			if (this.glitter) {
				star.sparkFreq = sparkFreq;
				star.sparkSpeed = sparkSpeed;
				star.sparkLife = sparkLife;
				star.sparkLifeVariation = sparkLifeVariation;
				star.sparkColor = this.glitterColor;
				star.sparkTimer = Math.random() * star.sparkFreq;
			}
        };

        if (typeof this.color === 'string') {
            if (this.color === 'random') {
                color = null; // false value creates random color in starFactory
            } else {
                color = this.color;
            }

            // Rings have positinal randomness, but are rotated randomly
            if (this.ring) {
                const ringStartAngle = Math.random() * Math.PI;
                const ringSquash = Math.pow(Math.random(), 2) * 0.85 + 0.15;

                createParticleArc(0, PI_2, this.starCount, 0, angle => {
                    // Create a ring, squashed horizontally
                	const initSpeedX = Math.sin(angle) * speed * ringSquash;
					const initSpeedY = Math.cos(angle) * speed;
					// Rotate ring
					const newSpeed = MyMath.pointDist(0, 0, initSpeedX, initSpeedY);
					const newAngle = MyMath.pointAngle(0, 0, initSpeedX, initSpeedY) + ringStartAngle;
					const star = Star.add(
						x,
						y,
						color,
						newAngle,
						// apply near cubic falloff to speed (places more particles towards outside)
						newSpeed,//speed,
						// add minor variation to star life
						this.starLife + Math.random() * this.starLife * this.starLifeVariation
                    );
                    
                    if (this.glitter) {
						star.sparkFreq = sparkFreq;
						star.sparkSpeed = sparkSpeed;
						star.sparkLife = sparkLife;
						star.sparkLifeVariation = sparkLifeVariation;
						star.sparkColor = this.glitterColor;
						star.sparkTimer = Math.random() * star.sparkFreq;
					}
                });
            }
            // Normal burst
            else {
                createBurst(this.starCount, starFactory);
            }
        }
        else if (Array.isArray(this.color)) {
            if (Math.random() < 0.5) {
                const start = Math.random() * Math.PI;
				const start2 = start + Math.PI;
				const arc = Math.PI;
				color = this.color[0];
				// Not creating a full arc automatically reduces star count.
				createBurst(this.starCount, starFactory, start, arc);
				color = this.color[1];
                createBurst(this.starCount, starFactory, start2, arc);
            } else {
				color = this.color[0];
				createBurst(this.starCount / 2, starFactory);
				color = this.color[1];
				createBurst(this.starCount / 2, starFactory);
            }
        }
        else {
            throw new Error('Invalid shell color. Expected string or array of strings, but received: ' + this.color);
        }

		if (this.pistil) {
			const innerShell = new Shell({
				spreadSize: this.spreadSize * 0.5,
				starLife: this.starLife * 0.6,
				starLifeVariation: this.starLifeVariation,
				starDensity: 1.4,
				color: this.pistilColor,
				glitter: 'light',
				glitterColor: this.pistilColor === COLOR.Gold ? COLOR.Gold : COLOR.White
			});
			innerShell.burst(x, y);
        }
        
        if (this.streamers) {
			const innerShell = new Shell({
				spreadSize: this.spreadSize * 0.9,
				starLife: this.starLife * 0.8,
				starLifeVariation: this.starLifeVariation,
				starCount: Math.floor(Math.max(6, this.spreadSize / 45)),
				color: COLOR.White,
				glitter: 'streamer'
			});
			innerShell.burst(x, y);
        }
        
        // Queue burst flash render
        BurstFlash.add(x, y, this.spreadSize / 4);

        // Play sound, but only for "original" shell, the one that was launched.
		// We don't want multiple sounds from pistil or streamer "sub-shells".
        // This can be detected by the presence of a comet.
        if (this.comet) {
            // Scale explosion sound based on current shell size and selected (max) shell size.
			// Shooting selected shell size will always sound the same no matter the selected size,
			// but when smaller shells are auto-fired, they will sound smaller. It doesn't sound great
			// when a value too small is given though, so instead of basing it on proportions, we just
			// look at the difference in size and map it to a range known to sound good.
			const maxDiff = 2;
			const sizeDifferenceFromMaxSize = Math.min(maxDiff, shellSizeSelector() - this.shellSize);
			const soundScale = (1 - sizeDifferenceFromMaxSize / maxDiff) * 0.3 + 0.7;
			soundManager.playSound('burst', soundScale);
        }
    }
}


const BurstFlash = {
	active: [],
	_pool: [],
	
	_new() {
		return {}
	},
	
	add(x, y, radius) {
		const instance = this._pool.pop() || this._new();
		
		instance.x = x;
		instance.y = y;
		instance.radius = radius;
		
		this.active.push(instance);
		return instance;
	},
	
	returnInstance(instance) {
		this._pool.push(instance);
	}
};


// Helper to generate objects for storing active particles.
// Particles are stored in arrays keyed by color (code, not name) for improved rendering performance.
function createParticleCollection() {
	const collection = {};
	COLOR_CODES_W_INVIS.forEach(color => {
		collection[color] = [];
	});
	return collection;
}


// STAR PROPERTIES (WIP)
// ---------------------
// transitionTime - how close to end of life that star transition happens

const Star = {
	// Visual properties
	drawWidth: 3,
	airDrag: 0.98,
	airDragHeavy: 0.992,
	
	// Star particles will be keyed by color
	active: createParticleCollection(),
	_pool: [],
	
	_new() {
		return {};
	},

	add(x, y, color, angle, speed, life, speedOffX, speedOffY) {
		const instance = this._pool.pop() || this._new();
		
		instance.visible = true;
		instance.heavy = false;
		instance.x = x;
		instance.y = y;
		instance.prevX = x;
		instance.prevY = y;
		instance.color = color;
		instance.speedX = Math.sin(angle) * speed + (speedOffX || 0);
		instance.speedY = Math.cos(angle) * speed + (speedOffY || 0);
		instance.life = life;
		instance.fullLife = life;
		instance.spinAngle = Math.random() * PI_2;
		instance.spinSpeed = 0.8;
		instance.spinRadius = 0;
		instance.sparkFreq = 0; // ms between spark emissions
		instance.sparkSpeed = 1;
		instance.sparkTimer = 0;
		instance.sparkColor = color;
		instance.sparkLife = 750;
		instance.sparkLifeVariation = 0.25;
		instance.strobe = false;
		
		this.active[color].push(instance);
		return instance;
	},

	// Public method for cleaning up and returning an instance back to the pool.
	returnInstance(instance) {
		// Call onDeath handler if available (and pass it current star instance)
		instance.onDeath && instance.onDeath(instance);
		// Clean up
		instance.onDeath = null;
		instance.secondColor = null;
		instance.transitionTime = 0;
		instance.colorChanged = false;
		// Add back to the pool.
		this._pool.push(instance);
	}
};


const Spark = {
	// Visual properties
	drawWidth: 0, // set in `configDidUpdate()`
	airDrag: 0.9,
	
	// Star particles will be keyed by color
	active: createParticleCollection(),
	_pool: [],
	
	_new() {
		return {};
	},

	add(x, y, color, angle, speed, life) {
		const instance = this._pool.pop() || this._new();
		
		instance.x = x;
		instance.y = y;
		instance.prevX = x;
		instance.prevY = y;
		instance.color = color;
		instance.speedX = Math.sin(angle) * speed;
		instance.speedY = Math.cos(angle) * speed;
		instance.life = life;
		
		this.active[color].push(instance);
		return instance;
	},

	// Public method for cleaning up and returning an instance back to the pool.
	returnInstance(instance) {
		// Add back to the pool.
		this._pool.push(instance);
	}
};


const soundManager = {
	baseURL: './assets/sounds/',
	ctx: new (window.AudioContext || window.webkitAudioContext),
	sources: {
		lift: {
			volume: 1,
			playbackRateMin: 0.85,
			playbackRateMax: 0.95,
			fileNames: [
				'lift1.mp3',
				'lift2.mp3',
				'lift3.mp3'
			]
		},
		burst: {
			volume: 1,
			playbackRateMin: 0.8,
			playbackRateMax: 0.9,
			fileNames: [
				'burst1.mp3',
				'burst2.mp3'
			]
		},
		burstSmall: {
			volume: 0.25,
			playbackRateMin: 0.8,
			playbackRateMax: 1,
			fileNames: [
				'burst-sm-1.mp3',
				'burst-sm-2.mp3'
			]
		},
		crackle: {
			volume: 0.2,
			playbackRateMin: 1,
			playbackRateMax: 1,
			fileNames: ['crackle1.mp3']
		},
		crackleSmall: {
			volume: 0.3,
			playbackRateMin: 1,
			playbackRateMax: 1,
			fileNames: ['crackle-sm-1.mp3']
		}
	},

	preload() {
		const allFilePromises = [];

		function checkStatus(response) {
			if (response.status >= 200 && response.status < 300) {
				return response;
			}
			const customError = new Error(response.statusText);
			customError.response = response;
			throw customError;
		}

		const types = Object.keys(this.sources);
		types.forEach(type => {
			const source = this.sources[type];
			const { fileNames } = source;
			const filePromises = [];
			fileNames.forEach(fileName => {
				const fileURL = this.baseURL + fileName;
				// Promise will resolve with decoded audio buffer.
				const promise = fetch(fileURL)
					.then(checkStatus)
					.then(response => response.arrayBuffer())
					.then(data => new Promise(resolve => {
						this.ctx.decodeAudioData(data, resolve);
					}));

				filePromises.push(promise);
				allFilePromises.push(promise);
			});

			Promise.all(filePromises)
				.then(buffers => {
					source.buffers = buffers;
				});
		});

		return Promise.all(allFilePromises);
	},
	
	pauseAll() {
		this.ctx.suspend();
	},

	resumeAll() {
		// Play a sound with no volume for iOS. This 'unlocks' the audio context when the user first enables sound.
		this.playSound('lift', 0);
		// Chrome mobile requires interaction before starting audio context.
		// The sound toggle button is triggered on 'touchstart', which doesn't seem to count as a full
		// interaction to Chrome. I guess it needs a click? At any rate if the first thing the user does
		// is enable audio, it doesn't work. Using a setTimeout allows the first interaction to be registered.
		// Perhaps a better solution is to track whether the user has interacted, and if not but they try enabling
		// sound, show a tooltip that they should tap again to enable sound.
		setTimeout(() => {
			this.ctx.resume();
		}, 250);
	},
	
	// Private property used to throttle small burst sounds.
	_lastSmallBurstTime: 0,

	/**
	 * Play a sound of `type`. Will randomly pick a file associated with type, and play it at the specified volume
	 * and play speed, with a bit of random variance in play speed. This is all based on `sources` config.
	 *
	 * @param  {string} type - The type of sound to play.
	 * @param  {?number} scale=1 - Value between 0 and 1 (values outside range will be clamped). Scales less than one
	 *                             descrease volume and increase playback speed. This is because large explosions are
	 *                             louder, deeper, and reverberate longer than small explosions.
	 *                             Note that a scale of 0 will mute the sound.
	 */
	playSound(type, scale=1) {
		// Ensure `scale` is within valid range.
		scale = MyMath.clamp(scale, 0, 1);

		// Disallow starting new sounds if sound is disabled, app is running in slow motion, or paused.
		// Slow motion check has some wiggle room in case user doesn't finish dragging the speed bar
		// *all* the way back.
		if (!canPlaySoundSelector() || simSpeed < 0.95) {
			return;
		}
		
		// Throttle small bursts, since floral/falling leaves shells have a lot of them.
		if (type === 'burstSmall') {
			const now = Date.now();
			if (now - this._lastSmallBurstTime < 20) {
				return;
			}
			this._lastSmallBurstTime = now;
		}
		
		const source = this.sources[type];

		if (!source) {
			throw new Error(`Sound of type "${type}" doesn't exist.`);
		}
		
		const initialVolume = source.volume;
		const initialPlaybackRate = MyMath.random(
			source.playbackRateMin,
			source.playbackRateMax
		);
		
		// Volume descreases with scale.
		const scaledVolume = initialVolume * scale;
		// Playback rate increases with scale. For this, we map the scale of 0-1 to a scale of 2-1.
		// So at a scale of 1, sound plays normally, but as scale approaches 0 speed approaches double.
		const scaledPlaybackRate = initialPlaybackRate * (2 - scale);
		
		const gainNode = this.ctx.createGain();
		gainNode.gain.value = scaledVolume;

		const buffer = MyMath.randomChoice(source.buffers);
		const bufferSource = this.ctx.createBufferSource();
		bufferSource.playbackRate.value = scaledPlaybackRate;
		bufferSource.buffer = buffer;
		bufferSource.connect(gainNode);
		gainNode.connect(this.ctx.destination);
		bufferSource.start(0);
	}
};


// Kick things off.

function setLoadingStatus(status) {
    document.querySelector('.loading-init__status').textContent = status;
}

// Allow status to render, then preload assets and start app.
setLoadingStatus('Lighting Fuses');
setTimeout(() => {
    soundManager.preload()
    .then(
        init,
        reason => {
            init();
            return Promise.reject(reason);
        }
    );
}, 0);