**Demo**: Particles colliding with each other in space. Move the pointer to hit them like billiard balls. ptsjs.org/demo 
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// Source code licensed under Apache License 2.0. // Copyright © 2017 William Ngan. (https://github.com/williamngan/pts) window.demoDescription = "Particles colliding with each other in space. Move the pointer to hit them like billiard balls."; Pts.quickStart( "#pt", "#123" ); //// Demo code starts (anonymous function wrapper is optional) --- (function() { var world; space.add( { start: (bound, space) => { // Create world and 100 random points world = new World( space.innerBound, 1, 0 ); let pts = Create.distributeRandom( space.innerBound, 100 ); // Create particles and hit them with a random impulse for (let i=0, len=pts.length; i<len; i++) { let p = new Particle( pts[i] ).size( (i===0) ? 30 : 3+Math.random()*space.size.x/50 ); p.hit( Num.randomRange(-50,50), Num.randomRange(-25, 25) ); world.add( p ); } world.particle( 0 ).lock = true; // lock it to move it by pointer later on }, animate: (time, ftime) => { world.drawParticles( (p, i) => { let color = (i===0) ? "#fff" : ["#ff2d5d", "#42dc8e", "#2e43eb", "#ffe359"][i%4]; form.fillOnly( color ).point( p, p.radius, "circle" ) }); world.update( ftime ); }, action:( type, px, py) => { if (type == "move") { world.particle( 0 ).position = new Pt(px, py); } }, resize: (bound, evt) => { if (world) world.bound = space.innerBound; } }); space.bindMouse().bindTouch(); space.play(); })();