Okay, so I bought these mermaid puzzles for my 4-year-old niece and OMG she's obsessed! The magnets actually work (shocking for kids' toys these days) and the pieces stay put unless she starts doing her dramatic 'ta-da!' flips.
The 3-in-1 difficulty levels are genius - we started with the 42-piece puzzle and she's already mastering the 52-piece one. The colors are so vibrant but not neon-bright (thank you, eye-friendly matte finish!).
Major bonus: this thing survived a 6-hour car trip AND a juice spill. The cardboard is thicker than my last online date's excuses. We did lose two pieces when she opened it mid-car-ride though (lesson learned!).
Educational win: I've caught her 'teaching' her stuffed animals how to solve the puzzles. Her concentration has improved so much she actually sits still for more than 3 minutes now (miracle!).
Only complaint? Now I have to buy the dinosaur version too because she won't stop asking for 'the puzzle with teeth'... worth every penny though!