Hey - thank you for playing Triz! I really appreciate the feedback. You are correct in that puzzles are randomly generated, which was a limitation we faced making the game during the jam. However, there is a way to solve puzzles with an odd number of triangles!
You can position your cursor to a spot like this and be able to affect an odd number of triangles, so it’s not entirely impossible. Probably not the best way to do it, but it’s possible!