JS1k: The JavaScript code golfing competition

a=Math,b=a.random,c=[],j=document.getElementById("c"),k=j.getContext("2d"),m=window,n=(W=m.innerWidth)/2,q=(H=m.innerHeight)/2,r=M=1;function s(o,p,u,v){k.fillStyle=o;k.beginPath();k.arc(p,u,v,0,a.PI*2,0);k.closePath();k.fill()}function t(o,p){for(g=40;g--;)if(!c[g]){c[g]={x:o||n,y:p||q,d:o?b()*4-2:0,e:p?b()*4-2:0,b:1,a:0,c:b()>.5};return}}with(j.style){position="fixed";top=left=0}j.width=W;j.height=H;for(f=40;f--;)c[f]=0;for(f=9;f--;)t(); m.setInterval(function(){k.fillStyle="rgba(9,9,9,.2)";k.fillRect(0,0,W,H);for(f=40;f--;)if(d=c[f])if(d.a>1E3)c[f]=0;else{l=d.a/1E3;h=l*7;d.d+=b()*.1*(n-d.x>1?1:n-d.x<-1?-1:n-d.x);d.e+=b()*.1*(q-d.y>1?1:q-d.y<-1?-1:q-d.y);d.x+=d.d;d.y+=d.e;d.a++;i=d.c?"rgba(49,153,255,":"rgba(255,49,166,";h=1-l;s(i+h+")",d.x,d.y,1+l*12);s(i+h/2+")",d.x,d.y,1+l*16);d.b&&d.b--;if(d.b==0&&d.a>250&&d.a<750&&b()>.9)for(g=40;g--&&!d.b;)if((e=c[g])&&e!=d&&e.a>=d.a){i=a.sqrt(d.x-e.x,d.y-e.y);if(i>-5&&i<5&&d.c!=e.c){t(d.x, d.y);d.b=e.b=10}}}r=n>W||n<0?-r:r;M=q>H||q<0?-M:M;n+=r;q+=M},40);

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/* SWARMS (v1.7)
 * by Barry van Oudtshoorn (www.barryvan.com.au)
 * A re-implementation of http://www.barryvan.com.au/demos/swarms/swarms.html,
 * which in turn is a reimplementation of a Processing script that I wrote. :)
 *
 * Male and female particles move around a central point, gradually aging.
 * When they reach maturity, they may interact with a particle of the opposite
 * sex to spawn a new particle. As they grow old, they become larger and slower
 * until they eventually die.
 *
 * Revisions (really, these version numbers are all but meaningless!)
 * 1.0 (1023B)
 * 	- Initial code.
 * 1.5 (1017B)
 * 	- Moved to Closure compiler to reduce size
 * 	- Some slight tweaks to particle movement
 * 	- Canvas now positioned to get rid of annoying border (try fullscreen!)
 * 1.7 (1011B)
 * 	- The swarm centre now moves around (simple bouncing). This allows the
 * 		particles to pick up a bit more speed, and move in more interesting ways;
 * 		where before they tended to just 'bubble' in the middle of the screen,
 * 		the swarm, as an entity, now appears more fluid and organic.
 * 	- Bugfix to spawning: particles now actually have to be near to each other
 * 		in BOTH axes to spawn, and both particles have to be of suitable age. This
 * 		prevents billions of particles from spawning from a single one.
 * 	- Reduced the total number of particles for aesthetic reasons
 * 	- Did some more "by-hand" optimisations after running it through the closure
 * 		compiler, like removing global variable declarations when I'm not
 * 		instantiating the variables there and then and removing the leading 0 on
 * 		decimal values to conserve precious bytes. With each revision, despite
 * 		adding functionality each time, the size is going down! :D
 *
 * Copyright 2010 Barry van Oudtshoorn.
 */

var z = function(a, b, c) { // Normalise a to between b and c
	return (a / (c - b));
},
h = function(a, b, c) { // Limx a to between b and c
	return (a > b ? b : (a < c ? c : a));
},
// I strip out all of the uninitialised declarations after compilation;
// they're globals anyway. I know it's not stylish, but it saves bytes!
r,s, // Particles that we're currently interested in
i,j, // Iterators
u,d, // Working variables
m = Math, // Alias
v = m.random, // Alias
p = [], // The particles
e = document.getElementById('c'), // The canvas element
t = e.getContext('2d'), // The context
n, // The normalised age of a particle
Q = window, // Alias
X = (W = Q.innerWidth)/2, // The swarm's COG
Y = (H = Q.innerHeight)/2,
N = M = 1, // The components of the velocity of the swarm's COG
q = function(a, b, c, f) { // Draw a blob
	t.fillStyle = a;
	t.beginPath();
	t.arc(b, c, f, 0, m.PI*2, 0);
	t.closePath();
	t.fill();
},

x = function() { // Global iterator
	//t.globalCompositeOperation = 'source-over'; // This is prettier, but "globalCompositeOperation" takes too many bytes! :(
	t.fillStyle = 'rgba(9,9,9,.2)';
	t.fillRect(0,0,W,H);
	//t.globalCompositeOperation = 'lighter';
   
	for (i = 40; i--;) { // Loop over all of the particles
		if (r = p[i]) {
			if (r.a > 1E3) {
				p[i] = 0; // Kill off old particles; use 0 because it's shorter than false, null, or using delete.
			} else {
				// Move the particle
				n = z(r.a, 0, 1E3);
				u = n * 7;
				r.X += v() * .1 * h(X - r.x, 1, -1); // Update the particle's velocity.
				r.Y += v() * .1 * h(Y - r.y, 1, -1);
				r.x += r.X; // Update the particle's coordinates based on its velocity.
				r.y += r.Y;
				r.a++; // Increment the particle's age
			   
				// Draw the particle
				
				d = r.s ? 'rgba(49,153,255,' : 'rgba(255,49,166,'; // The colour of the particle
				u = 1 - n; // The opacity of the particle; n is the normalised age
				q(d + u + ')', r.x, r.y, 1 + n * 12); // Draw the primary particle blob
				q(d + (u/2) + ')', r.x, r.y, 1 + n * 16); // We draw a lighter, larger blob for a 'glow' effect
				
				r.f && r.f--; // If we've spawned, decrement the cooldown.
				
				if (r.f == 0 && r.a > 250 && r.a < 750 && v() > 0.9) { // If we're the right age, check if we can spawn!
					for (j = 40; j-- && !r.f;) { // We have to loop over the particles again, and see if we're close enough to spawn.
						if ((s = p[j]) && s != r && s.a >= r.a) {
							d = m.sqrt(r.x - s.x, r.y - s.y); // Two if statements to avoid this calculation if possible
							if (d > -5 && d < 5 && r.s != s.s) { // Collision detection? What's that? :P
								y(r.x, r.y); // Spawn a new particle!
								r.f = s.f = 10; // Enforce the spawning cooldown
							}
						}
					}
				}
			}
		}
	}
	
	// Bounce the swarm's COG around the canvas
	N = (X > W || X < 0 ? -N : N);
	M = (Y > H || Y < 0 ? -M : M);
	X += N;
	Y += M;
},

// Spawn a new particle. If sx and sy are defined, they will be its initial
// coordinates; otherwise, we just the COG. If sx and sy are defined, we also
// give the particle a random velocity; this means that they're 'flung out'
// from their parents; at startup, though, we want them all nicely bunched.
y = function(sx,sy) {
	for (j = 40; j--;) {
		if (!p[j]) {
			p[j] = {
				x: sx || X, // The particle's coords
				y: sy || Y,
				X: sx ? v() * 4 - 2: 0, // The particles velocity
				Y: sy ? v() * 4 - 2 : 0,
				f: 1, // Cooldown after spawning
				a: 0, // The age of the particle
				s: v() > .5 // The sex of the particle
			}
			return;
		}
	}
};

// Make the canvas fill the entire screen
with (e.style) {
	position = 'fixed';
	top = left = 0;
}
e.width = W; // Set the canvas width and height
e.height = H;

for (i = 40; i--;) p[i] = 0; // Populate initial particles
for (i = 9; i--;) y(); // Spawn eight particles. A number < 10 saves a byte! :P

Q.setInterval(x, 40); // Make it go.