[Hugsun]

I solved a hard puzzle on chromium and noticed a lag when picking pieces up but dragging them around was smooth.

Another tip is to make scrolling or some keyboard buttons rotate the pieces, snapping to 90° angles would be a good start. Making the pieces only snap when placed down instead of just when they are close to a compatible piece might also be good.

These things could be togglable or vary between the difficulty modes.

In any case, cool project and good luck with it!