nctions.....................................................

    function drawGrid(color, stepx, stepy) {
        context.save()

        context.shadowColor = undefined;
        context.shadowBlur = 0;
        context.shadowOffsetX = 0;
        context.shadowOffsetY = 0;

        context.strokeStyle = color;
        context.fillStyle = '#ffffff';
        context.lineWidth = 0.5;
        context.fillRect(0, 0, context.canvas.width, context.canvas.height);

        for (var i = stepx + 0.5; i < context.canv