Warlock's Tower [Steam store page]
I quite enjoyed this, although about 45 minutes in I'm already 100% done with 2 out of 5 worlds and well on my way to finishing the third, and the game still doesn't seem as "punishing" as the store description would lead you to believe.

There's no downside to losing or restarting a level, and the "brutal rule" of one move, one life lost, is the core puzzle mechanic of the game - you count your steps to nearby life pickups, and figure out the order you need to survive.

This gets more challenging when enemies move at certain intervals as well, but I only found one level so far where that really complicated matters. Overall it was a relaxing and enjoyable puzzle experience so far.

DifficultIndiePuzzleRetroLink
Hotline Miami [Steam store page]
Prepare to enjoy smashing open heads with a bat, slitting throats, and shooting enemies at breakneck speed in a psychedelic environment.

For me this game fell somewhere between Legend of Grimrock and Legend of Grimrock 2 - not quite as good as the open-world of the second game, but Vaporum's voice acting made it more of an engaging experience than the original Grimrock.

While this is a much cleaner game than And Yet It Moves, I am left wishing for better control granularity. In certain areas a mouse control scheme would reduce the number of deaths immensely. Luckily the checkpoints are frequent and lives unlimited

Revenge of the Titans [Steam store page]
A tower defence game that keeps you on your toes. There are tons of upgrades and not enough time to buy all of them - you definitely won't get through all the levels on the first try.