// Don't worry it'll take about 9x10^32 years before there's a stack overflow because of the timer counting up. vec4 scan(vec4 input_colour) { int gap = 8; if ((positionY + scaledTime) % gap == 0) { return input_colour - vec4(0.2, 0.2, 0.2, 0.0); } return input_colour; }