jsgame/js/ball.js

function Ball(options) {
	if (typeof(options) == 'undefined') options={};
	var x = options.x !== undefined ? options.x : 0;
	var y = options.y !== undefined ? options.y : 0;
	var dx = options.dx !== undefined ? options.dx : 0;
	var dy = options.dy !== undefined ? options.dy : 0;
	var sx = options.sx !== undefined ? options.sx : 0;
	var sy = options.sy !== undefined ? options.sy : 0;
	var size = options.size !== undefined ? options.size : 0;

	function update(ctx, paddle) {
		// Get the start x and y for the ball.
		var aX = x;
		var aY = y;

		// Move the ball left or right.
		x += dx * sx;

		// Check to see if the ball hit the left wall.
		// If it did, bounce to the right.
		if (x <= (size / 2)) {
			x = size / 2;
			dx = 1;
		}

		// Check to see if the ball hit the right wall.
		// If it did, bounce to the left.
		if (x >= (ctx.canvas.width - (size / 2))) {
			x = (ctx.canvas.width - (size / 2));
			dx = -1;
		}

		// Move the ball up or down.
		y += dy * sy;

		// Check to see if the ball hit the ceiling.
		// Bounce down if it did.
		if (y <= (size / 2)) {
			y = size / 2;
			dy = 1;
		}

		// Check to see if the ball hit the paddle.
		// Ball line aX, aY to x, y
		// Paddle line paddle.x - (paddle.size / 2), paddle.y to paddle.x + (paddle.size / 2), paddle.y
		// y = mx + b
		if (x >= paddle.getX1() &&
			x <= paddle.getX2() &&
			aY <= paddle.getY() && y >= paddle.getY()) {
			y = paddle.getY() - size;
			dy = -1;
			sx++;
			sy++;
			paddle.increaseDifficulty();
			game.add1ToScore();
		}

		// Check to see if the ball goes off the bottom
		// of the screen. If it did, game over!
		if (y >= (ctx.canvas.height - (size / 2))) {
			game.endGame();
		}
	}

	function draw(ctx) {
		ctx.beginPath();
		ctx.fillStyle = '#000000';
		ctx.ellipse(x, y, size, size, 0, 0, 360);
		ctx.fill();
	}

	return {
		'x': x,
		'y': y,
		'dx': dx,
		'dy': dy,
		'sx': sx,
		'sy': sy,
		'size': size,
		'update': update,
		'draw': draw
	};
}