ctions for better readability)
		context.font = "14px Arial";
		context.fillStyle = "#444444";
		context.textAlign = "center";
		context.textBaseline = "middle";
		context.strokeStyle = "#000000";
		context.lineWidth = 1;
		context.beginPath();

		context.moveTo(20.5, sharp(y2s(0)));
		context.lineTo(w - 20.5, sharp(y2s(0)));
		context.moveTo(sharp(x2s(0)), h - 20.5);
		context.lineTo(sharp(x2s(0)), 20.5);
		context.stroke();
		context.closePath();

		context.beginPath();
		context.setLineDash([3, 2]);
		co