<canvas id="bgCanvas"></canvas>
<canvas id="terCanvas"></canvas>
<script>
(function() {
var requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame ||
window.webkitRequestAnimationFrame || window.msRequestAnimationFrame ||
function(callback) {
window.setTimeout(callback, 1000 / 60);
};
window.requestAnimationFrame = requestAnimationFrame;
})();
// Terrain stuff.
var terrain = document.getElementById("terCanvas"),
background = document.getElementById("bgCanvas"),
terCtx = terrain.getContext("2d"),
bgCtx = background.getContext("2d"),
width = window.innerWidth,
height = document.body.offsetHeight;
(height < 400) ? height = 400: height;
terrain.width = background.width = width;
terrain.height = background.height = height;
// Some random points
var points = [],
displacement = 140,
power = Math.pow(2, Math.ceil(Math.log(width) / (Math.log(2))));
// set the start height and end height for the terrain
points[0] = (height - (Math.random() * height / 2)) - displacement;
points[power] = (height - (Math.random() * height / 2)) - displacement;
// create the rest of the points
for (var i = 1; i < power; i *= 2) {
for (var j = (power / i) / 2; j < power; j += power / i) {
points[j] = ((points[j - (power / i) / 2] + points[j + (power / i) /
2]) / 2) + Math.floor(Math.random() * -displacement +
displacement);
}
displacement *= 0.6;
}
// draw the terrain
terCtx.beginPath();
for (var i = 0; i <= width; i++) {
if (i === 0) {
terCtx.moveTo(0, points[0]);
} else if (points[i] !== undefined) {
terCtx.lineTo(i, points[i]);
}
}
terCtx.lineTo(width, terrain.height);
terCtx.lineTo(0, terrain.height);
terCtx.lineTo(0, points[0]);
terCtx.fill();
// Second canvas used for the stars
bgCtx.fillStyle = '#05004c';
bgCtx.fillRect(0, 0, width, height);
// stars
function Star(options) {
this.size = Math.random() * 2;
this.speed = Math.random() * .1;
this.x = options.x;
this.y = options.y;
}
Star.prototype.reset = function() {
this.size = Math.random() * 2;
this.speed = Math.random() * .1;
this.x = width;
this.y = Math.random() * height;
}
Star.prototype.update = function() {
this.x -= this.speed;
if (this.x < 0) {
this.reset();
} else {
bgCtx.fillRect(this.x, this.y, this.size, this.size);
}
}
function ShootingStar() {
this.reset();
}
ShootingStar.prototype.reset = function() {
this.x = Math.random() * width;
this.y = 0;
this.len = (Math.random() * 80) + 10;
this.speed = (Math.random() * 10) + 6;
this.size = (Math.random() * 1) + 0.1;
// this is used so the shooting stars arent constant
this.waitTime = new Date().getTime() + (Math.random() * 3000) + 500;
this.active = false;
}
ShootingStar.prototype.update = function() {
if (this.active) {
this.x -= this.speed;
this.y += this.speed;
if (this.x < 0 || this.y >= height) {
this.reset();
} else {
bgCtx.lineWidth = this.size;
bgCtx.beginPath();
bgCtx.moveTo(this.x, this.y);
bgCtx.lineTo(this.x + this.len, this.y - this.len);
bgCtx.stroke();
}
} else {
if (this.waitTime < new Date().getTime()) {
this.active = true;
}
}
}
var entities = [];
// init the stars
for (var i = 0; i < height; i++) {
entities.push(new Star({
x: Math.random() * width,
y: Math.random() * height
}));
}
// Add 2 shooting stars that just cycle.
entities.push(new ShootingStar());
entities.push(new ShootingStar());
//animate background
function animate() {
bgCtx.fillStyle = '#05004c';
bgCtx.fillRect(0, 0, width, height);
bgCtx.fillStyle = '#ffffff';
bgCtx.strokeStyle = '#ffffff';
var entLen = entities.length;
while (entLen--) {
entities[entLen].update();
}
requestAnimationFrame(animate);
}
animate();
</script></script>
