game.js

/*
    LittleJS Hello World Starter Game
*/

'use strict';

// popup errors if there are any (help diagnose issues on mobile devices)
if (debug)
    onerror = (...parameters)=> alert(parameters);

// game variables
let particleEmiter, clickCount = 0;

// sound effects
const sound_click = new Sound([.5,.5]);

// medals
const medal_example    = new Medal(0, 'Example Medal', 'Medal description goes here.');
medalsInit('Hello World');

///////////////////////////////////////////////////////////////////////////////
function gameInit()
{
    // create tile collision and visible tile layer
    initTileCollision(vec2(32,16));
    const tileLayer = new TileLayer(vec2(), tileCollisionSize);
    const pos = vec2();

    // get level data from the tiles image
    const imageLevelDataRow = 1;
    mainContext.drawImage(tileImage,0,0);
    for (pos.x = tileCollisionSize.x; pos.x--;)
    for (pos.y = tileCollisionSize.y; pos.y--;)
    {
        const data = mainContext.getImageData(pos.x, 16*(imageLevelDataRow+1)-pos.y-1, 1, 1).data;
        if (data[0])
        {
            setTileCollisionData(pos, 1);

            const tileIndex = 1;
            const direction = randInt(4)
            const mirror = randInt(2);
            const color = randColor();
            const data = new TileLayerData(tileIndex, direction, mirror, color);
            tileLayer.setData(pos, data);
        }
    }
    tileLayer.redraw();

    // move camera to center of collision
    cameraPos = tileCollisionSize.scale(.5);
    cameraScale = 32;

    // enable gravity
    gravity = -.01;

    // create particle emitter
    const center = tileCollisionSize.scale(.5).add(vec2(0,9));
    particleEmiter = new ParticleEmitter(
        center, 0, 1, 0, 500, PI, // pos, angle, emitSize, emitTime, emitRate, emiteCone
        0, vec2(16),                            // tileIndex, tileSize
        new Color(1,1,1),   new Color(0,0,0),   // colorStartA, colorStartB
        new Color(1,1,1,0), new Color(0,0,0,0), // colorEndA, colorEndB
        2, .2, .2, .1, .05,     // particleTime, sizeStart, sizeEnd, particleSpeed, particleAngleSpeed
        .99, 1, 1, PI, .05,     // damping, angleDamping, gravityScale, particleCone, fadeRate, 
        .5, 1, 1                // randomness, collide, additive, randomColorLinear, renderOrder
    );
    particleEmiter.elasticity = .3;
    particleEmiter.trailScale = 2;
}

///////////////////////////////////////////////////////////////////////////////
function gameUpdate()
{
    if (mouseWasPressed(0))
    {
        // play sound when mouse is pressed
        sound_click.play(mousePos);

        // change particle color
        particleEmiter.colorStartA = new Color;
        particleEmiter.colorStartB = randColor();
        particleEmiter.colorEndA = particleEmiter.colorStartA.scale(1,0);
        particleEmiter.colorEndB = particleEmiter.colorStartB.scale(1,0);

        // unlock medals
        medal_example.unlock();
    }

    // move particles to mouse location if on screen
    if (mousePosScreen.x || mousePosScreen.y)
        particleEmiter.pos = mousePos;
}

///////////////////////////////////////////////////////////////////////////////
function gameUpdatePost()
{

}

///////////////////////////////////////////////////////////////////////////////
function gameRender()
{
    // draw a grey square in the background without using webgl
    drawRect(cameraPos, tileCollisionSize.add(vec2(5)), new Color(.2,.2,.2), 0, 0);
}

///////////////////////////////////////////////////////////////////////////////
function gameRenderPost()
{
    // draw to overlay canvas for hud rendering
    const drawText = (text, x, y, size=70) =>
    {
        overlayContext.textAlign = 'center';
        overlayContext.textBaseline = 'top';
        overlayContext.font = size + 'px arial';
        overlayContext.fillStyle = '#fff';
        overlayContext.lineWidth = 3;
        overlayContext.strokeText(text, x, y);
        overlayContext.fillText(text, x, y);
    }
    drawText('Hello World', overlayCanvas.width/2, 40);
}

///////////////////////////////////////////////////////////////////////////////
// Startup LittleJS Engine
engineInit(gameInit, gameUpdate, gameUpdatePost, gameRender, gameRenderPost, 'tiles.png');