Boy and his Blob

[10,000 Volt Ghost]

It's on my to do list.

[MarioRPG]

I've played about 5 levels. As such, there is no real challenge as of yet. However, I can see the progression in the puzzles and can see it getting reasonably tough (ie there are 8 slots for jellybeans, as of now it's only ever used 4). But the controls are slick, and you can easily alter the flight path of jellybeans etc. Not much of a learning curve, but it teaches you how to multi-use transformations - such as trapping enemies with the "hole".
The game is beautiful and cute as hell. There is a hug button for crying out loud.