var siny = Math.sin(((x + time / 17) * 4 * Math.PI) / width);
// convert to range 0 to 1
siny = (siny + 2) / 4;
siny = siny * height;

var thickness = (Math.sin(time / 500) * 3 + 5);
var dist = Math.min(Math.abs(y - siny) / thickness, 1);

return Math.floor((1 - dist) * 255);