flappydick/js/vec2.js

function Vec2(x, y) {
	this.x = x || 0;
	this.y = y || 0;
	return this;
}

Vec2.prototype.clone = function() {
	return new Vec2(this.x, this.y);
}

Vec2.prototype.length = function() {
	return Math.sqrt((this.x * this.x) + (this.y * this.y));
}

Vec2.prototype.set = function(vec) {
	this.x = vec.x;
	this.y = vec.y;

	return this;
}

Vec2.prototype.add = function(vec) {
	this.x += vec.x;
	this.y += vec.y;

	return this;
}

Vec2.prototype.sub = function(vec) {
	this.x -= vec.x;
	this.y -= vec.y;

	return this;
}

Vec2.prototype.scale = function(num) {
	this.x *= num;
	this.y *= num;

	return this;
}

Vec2.prototype.normalize = function() {
	var len = this.length();

	if (len === 0) {
		this.x = 1;
		this.y = 0;
	} else {
		this.scale(1 / len);
	}

	return this;
}

Vec2.prototype.rotate = function(rad) {
	var x = this.x;
	var y = this.y;

	this.x = x * Math.cos(rad) - y * Math.sin(rad);
	this.y = y * Math.cos(rad) + x * Math.sin(rad);

	return this;
}

Vec2.prototype.angle = function() {
	return Math.atan2(this.y, this.x);
}