Thanks!
Sierpinkski 2 has a non-downscaling feedback loop (camera and display are the same size), which would cause the "rotating white block" thing when you assemble the parts normally (because when you move parts through parts by hand, it would leave trails everywhere, which won't dissipate because there's a non-downscaling loop). But this is what the stop/reset button on the top of the screen is for. (See the in-game level tips for more details)