JavaScriptでお絵描き

JavaScript で書いたコードはこんな感じです。

var callbacks = {};
var canvas;

function load()
{
    dashcode.setupParts();
    canvas = document.getElementById("canvas");
    if (canvas.getContext) {
        callbacks.draw(canvas.getContext("2d"));
    }
}

callbacks.draw = function(gc) {
    var X = canvas.width, Y = canvas.height, STEP = 3, x, y;
    gc.clearRect(0, 0, X, Y);
    gc.lineWidth = 1;
    gc.beginPath();
    for (y = 0; y <= Y; y = y + STEP) {
        gc.moveTo(0, 0);
        gc.lineTo(X - y, y);
    }
    gc.closePath();
    gc.stroke();
};