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HTML

              
                <canvas id="c"></canvas>
              
            
!

CSS

              
                body {
 background: #EEE;
 margin: 0;
 padding: 0;
}
              
            
!

JS

              
                
###
 Circle tunnel
    Author: Kushagra Gour a.k.a. Chin Chang
    (@chinchang457)
###
# requestanimationframe polyfill
window.requestAnimFrame = (->
  return  window.requestAnimationFrame       || 
		  window.webkitRequestAnimationFrame || 
		  window.mozRequestAnimationFrame    || 
		  window.oRequestAnimationFrame      || 
		  window.msRequestAnimationFrame     ||  
		  (callback) ->
			window.setTimeout callback, 1000 / 60
)();

PI_BY_180 = Math.PI / 180

# variables
canvas = null
ctx = null
num_particles = 500
display_list = []
last_time = null
spring_constant = 0.2
damping_constant = 0.08
colors = ['#0066CC']
W = window.innerWidth
H = window.innerHeight
cx = W / 2
cy = H / 2
time = 1

init = (e) ->
	canvas = document.getElementById 'c'
	ctx = canvas.getContext '2d'
	canvas.width = W
	canvas.height = H
	canvas.addEventListener 'mousemove', onMouseMove

	# create particles
	for i in [10...W/2] by 10
		for j in [0...10]
			display_list.push new Particle(i)

onMouseMove = (e) ->
	mx = e.offsetX || e.pageX
	my = e.offsetY || e.pageY
	time = mx / W
			
animate = ->
	animationLoop()
	requestAnimFrame animate

animationLoop = ->
	if !last_time then last_time = (new Date).getTime()
	current_time = (new Date).getTime()
	dt = (current_time - last_time) / 1000
	last_time = current_time
	window.fps = 1 / dt
	
	draw()
	update()

draw = ->
	ctx.fillStyle = "#111"
	ctx.fillRect 0, 0, W, H

	for child in display_list
		continue if typeof child.draw isnt 'function'
		ctx.save();
		ctx.translate child.x, child.y unless isNaN child.x or isNaN child.y 
		ctx.scale child.scale_x, child.scale_y unless isNaN child.scale_x or isNaN child.scale_y 
		ctx.globalAlpha = child.alpha unless isNaN child.alpha 
		child.draw()
		ctx.restore();

update = ->
	# update particles
	for child in display_list
		child.update() if typeof child.update is 'function'

class Particle
	constructor: (@radius = 1) ->
		@theta = ~~(Math.random() * 360)
		@speed_theta = 0.5 + Math.random() * @radius * 0.005
		@alpha = @radius / (W / 2)
		if Math.random() > 0.5 then @dir = 1 else @dir = -1
		@color = colors[0]
		@scale_x = @scale_y = 0.5
		
	draw: ->
		#ctx.drawImage canvas2, 0, 0
		ctx.fillStyle = @color
		ctx.beginPath()
		ctx.arc 0, 0, @radius*0.04, 0, Math.PI*2, true
		ctx.fill()

	update: ->
		@scale_x += @dir * 0.06 * time
		@scale_y += @dir * 0.06 * time
		@theta += @speed_theta * time
		@x = cx + @radius * Math.cos @theta * PI_BY_180
		@y = cy + @radius * Math.sin @theta * PI_BY_180

		if @scale_x > 1.5
			@scale_x = 1.5
			@dir = -1
		else if @scale_x < 0
			@scale_x = 0
			@dir = 1
        
	reset: ->
		@dir *= -1
		@scale_x = @scale_y = 0.5
		@color = colors[~~(Math.random() * colors.length)]

	reposition: ->
		@ox = @x = ~~(Math.random() * W)
		@oy = @y = 100 + ~~(Math.random() * 5)

init()
animate()
              
            
!
999px

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