Calibron 12
This is a (very rough) web version of the Calibron 12 puzzle from 1933. Like many people I discovered it through a Vsauce video and wanted to make it because I enjoy making puzzles much more than solving them. The goal is to order the pieces so that they fit neatly in the borders. There are 2 versions of this puzzle: with a spacer and without. There is only one solution without a spacer and a few dozens for each spacer. You can learn (so much) more info about this puzzle here.
This only works on desktop/laptop because I'm too lazy to try to make that work on tiny phones.
Right click to rotate pieces.