// [TODO] try add the flat edge on to the wafer
module wafer(d, exposure_size=3*25.4) {
    if ($preview) {
        color([128/255, 128/255, 128/255])
        translate([0, 0, -1])
        circle(r=d/2);

        color([255/255, 128/255, 128/255, 50/255])
        translate([0, 0, 3])
        difference() {
            circle(r=d/2);
            circle(r=exposure_size/2);
        }
    }
}