The Impressionists stopped mixing colour on the palette. Instead they laid broken color — small strokes of pure, unmixed pigment side by side — and let the mixing happen in the viewer's eye at a distance. That is optical mixing.
Your retina pools light from patches too small to resolve, averaging them together — very nearly the blur this bench computes. Step far enough back and the kernel that models your eye grows wider than the strokes, so the confetti fuses into coherent water, light and air.
The chemist Chevreul showed that complementary colours placed side by side make each other vibrate. Blue against orange, fused in the eye, stays luminous — the retina keeps the light while cancelling the hue. Stir those same two on a palette and you get dead brown.
So whether strokes fuse at all depends on their size against your distance — fat dabs need you to walk further back. "Step back" was never just advice for reading a painting; it is the other half of how the picture is made.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.