Good but not Euclidea
Challenging geometry puzzles, simple UI, pay if/what you want, no nags - what more could I ask for? Nit picking: the fixed 6x6 grid and the lack of zoom make some puzzles artificially difficult. Coin flip on whether skipping tedious puzzles should be allowed. But the elephant in the room is Euclidea. Not really fair to compare the two but many people will. I learned some geometry fundamentals from Euclidea. Some of the pyth60 puzzles are hard but I don’t think I learned anything. I passed up pyth60 for a long time, thinking the concept seemed a bit contrived, and IMO that instinct was correct. I worked through all the puzzles for a complete review. Some were just tedious - I used a calculator on several, and resorted to a spreadsheet on at least one centroid. So, challenging if you’re in the mood, and moderately rewarding.