The levels in Crystal Caves HD can be challenging. I often need a couple of attempts to get the jumps and the puzzles right. However, the game allows me to quickly learn from mistakes, since each attempt only takes at most a few minutes. It's fun to master a level like that in 15 or 20 minutes total. The addition of difficulty settings, achievements and a leaderboard provide nice incentives to get the most out of each level. And then there's also the level editor. All in all a lot of value for a small price.
