I've played a few puzzle games in this jam so far, here are those that kept me playing the longest. You should check them out if you are into them!

Quantum Splitter

The smoothest experience I've experienced in this jam. It's easy to get into, it gets just the right amount of hard and it's very satisfying.

https://ldjam.com/events/ludum-dare/49/quantum-madness

SCANLINE

A great sokoban where the main mechanic of the game is closest tied to the "Unstable" theme. https://ldjam.com/events/ludum-dare/49/scanline

Breakoban

It's quite a simple mechanic but they explore the concept quite well. It's pretty short (10 levels) so it's a treat to try and complete. https://ldjam.com/events/ludum-dare/49/breakoban

Among Monolyths

Nobody giving feedback could avoid the comparisons to the Witness, and it's hard for me to do it either. It is a fun mix between trying to understand the rules of the puzzles and then applying this knowledge to try and solve them, not unlike the Witness. The scope of it is also impressive for a jam. https://ldjam.com/events/ludum-dare/49/among-monolyths

Plains In The Sky

It's less of a thinking game compared to the previous two but it is still very inventive and probably the best looking entry I've seen so far. If you like physics puzzles, give it a try! https://ldjam.com/events/ludum-dare/49/plains-in-the-sky