 < data.length; i += 4) {
				if (data[i + 0] > 10 && data[i + 2] > 10 && data[i + 3] > 200) {
					// found purple overlap
					expected = true;
					purpleX = (i / 4) % canvas.width;
					purpleY = Math.floor((i / 4) / canvas.width);
					break;
				}
			}

			ctx.fillStyle = result ? "purple" : "transparent";
			ctx.beginPath();
			ctx.arc(0, 0, r / 6, 0, Math.PI * 2);
			ctx.fill();

			ctx.restore();

			/*
			// This is just to see that the purple detection is working right.
			if (expected) {
			  ct