Chemotaxis.pde

 //declare bacteria variables here  
 int[] colors = {#ff0000,#ff9d00, #ffee00,#21f20e ,#0ee2f1 ,#dc19ff ,#ff5e96}; 
 int currentColor = 0;
 Bacteria [] dots = new Bacteria[50];
 void setup()   
 {     
 	size(500,500); 
 	noStroke();
 	for(int a = 0; a < dots.length; a++){
 		dots[a] = new Bacteria();
 	}
 }   
 void draw()   
 {    
 	background(0);
 	for(int a = 0; a < dots.length; a++){
 		dots[a].show();
 		dots[a].move();
 	}
 	for(int a = 0; a < colors.length; a++){
 		fill(colors[a]);
 		rect(15 * (a + 1), 480, 10, 10);
 	}
 }  

void mouseReleased(){
	for(int a = 0; a < dots.length; a ++){
		dots[a].bursting = true;
		dots[a].counter = 0;
		dots[a].angle = Math.random()*2*Math.PI;
	}
	if(mouseY > 480 && mouseY < 490 && mouseX > 15 && mouseX < 15 * (colors.length + 1)){
		currentColor = (int)(mouseX / 15) - 1;
	}

 }
 int getSign(int n){
   return n < 0 ? -1: n == 0? 2 : 1;
 }
 class Bacteria    
 {    
 	int x,y,c,counter;
 	boolean bursting = false;
 	double angle;
 	Bacteria(){
 		x = 250;
 		y = 250;
 	}
 	void move(){
   int xTarget, yTarget;
 		if(bursting){
 			xTarget = (int)((Math.cos(angle)*50) + x);
 			yTarget = (int)((Math.sin(angle)*50) + y);  
       counter ++;
       if (counter > 30){
         bursting = false;
       }
     }else{
       xTarget = mouseX;
       yTarget = mouseY;
     }
      int xSign = getSign(xTarget - x);
      int ySign = getSign(yTarget - y);
      x += (int)(Math.random()*5*getSign(xSign)) + (-1 * xSign);
      y += (int)(Math.random()*5*getSign(ySign)) + (-1 * ySign);
 	}
 	void show(){
 		c = colors[currentColor];
 		fill(c);
 		ellipse(x,y,3,3);
 	}
 }