<custom name="ball" ball="this_element" just_created="true">

        <_ on="just_created"

            ball.x="mouse_pos_x" ball.y="mouse_pos_y"

            ball.speed_x="random(-2, 2)"

            ball.speed_y="random(-2, 2)"

            ball.fill_hue="random(360)"

            ball.just_created="false"></_>

        <circle

            color_mode="HSB"

            fill_color="fill_hue, 100, 100"

            stroke_color="mouse_over ? 0 : NONE"

            stroke_weight="5"></circle>

        <_ ball.x="ball.x + ball.speed_x" ball.y="ball.y + ball.speed_y"></_>

        <_ on="ball.x NO_MORE_THAN 0 OR ball.x AT_LEAST width" ball.speed_x="-ball.speed_x"></_>

        <_ on="ball.y NO_MORE_THAN 0 OR ball.y AT_LEAST height" ball.speed_y="-ball.speed_y"></_>

    </custom>

​

    <canvas width="window_width" height="window_height" canvas_background="255">

        <_ on="mouse_down" ball="create_canvas_element('p-ball')"></_>

    </canvas>

</_>