The hole a pop leaves behind, 30° off-axis, at 2×Play and Play-from at +10 mm (default profile) shift about 7.5 window px against the art; their original places are holes in Steam's base mosaic.
(a) Without the hole treatment (G2)The hole shows the window cover: a bright sliver of frosted room beside each control. That is why over-art pops stay at 0 mm (flag overArtPops off).
(b) With G2: hole = {shadow, fill}glassd draws the control's own shadow over the art's tone inside its hole: off-axis the sliver reads as the shadow of a floating capsule. AT-HV-OFFAXIS: no magenta debug fill wider than 2 px.