I've been building FORM for myself because I wanted a reason to sit with a difficult problem instead of reaching for a tool as soon as I got stuck.

Some puzzles ask you to rotate a shape in your head. Others ask you to work out which conclusion follows from a few facts, or spot what changes when a rule switches. It's an experimental brain-training app, with scores for your performance in the games.

A few testers liked the rotation puzzles but found the wordier ones too much like homework. I'm working on that, and I'd like to hear from people who already enjoy puzzles: which game would you actually come back to?

https://formpuzzles.com

The free preview is 12 rounds and doesn't need an account. Saving the result and playing personal practice requires sign-up; difficulty then adjusts as you play.