If anyone wants to crank the difficulty up to 11, I suggest the puzzle types "Towers" and "Unequal" at max size/difficulty. These puzzles can get hard much fast

If anyone wants to crank the difficulty up to 11, I suggest the puzzle types "Towers" and "Unequal" at max size/difficulty. These puzzles can get hard much faster than they have any right to - I play them whenever I feel worried that perhaps P = NP.