The puzzles are fun, challenging without being maddening, with the solutions making sense in retrospect, although they may not be obvious at first. There is no dying, although the cave is full of dangers. Characters immediately respawn if eaten, blown up, or squashed, with no major time penalty to the player.
The Cave's biggest flaw is that they designed the game for replay but hampered the replay value. Having finished the game with three characters, you'll want to select another three, so you can see their special levels. But now you have to redo all those generic levels again along the way and while you may want to do the former, you won't want to do the latter.
Doing a second or third run-through is fine for sidescrollers, platformers, action adventure titles and the like. But not the tedious steps of "solving" a puzzle you've previously completed. That is boring.
The developers would have been better off having all seven characters available (though only three per section), and making the game longer so that each level could be completed without repetition. Alternately, replays with new characters should allow the opportunity of skipping previously completed sections.
Another possibility suggests itself as well. If the characters' special abilities played a greater role in level completion beyond collectibles and achievements, a replay might take on new meaning. The same level might have to be played in an entirely different way based on the characters available, essentially meaning entirely different puzzles would be solved depending on who you have in your party.
Alas, it is not so. The choice of characters has little effect on how you play the game, which strikes me as a missed opportunity. That is a shame, since going through the game the first time was such great fun, I wish I could enjoy playing it again.
Make no mistake, though. That first playthrough is just enchanting. I think everyone should check this one out just once.
The Cave is rated T (Teen) by the ESRB for Fantasy Violence and Blood. It is also available on Xbox 360, PC, Mac, and WiiU