炫酷Canvas光线爆炸特效

function Branch( hue, x, y, angle, vel ) {
	var move = 15;
	this.x = x + rand( -move, move );
	this.y = y + rand( -move, move );
	this.points = [];
	this.angle = angle != undefined ? angle : rand( 0, Math.PI * 1 );
	this.vel = vel != undefined ? vel : rand( -4, 4 );
	this.spread = 0;
	this.tick = 0;
	this.hue = hue != undefined ? hue : 200;
	this.life = 1;
	this.decay = 0.0015;
	this.dead = false;
	
	this.points.push({
		x: this.x,
		y: this.y
	});
}