Edge Online has highlighed a couple of really creative casual games that are worth five minutes of your time. In the first, you use a paint brush to “draw” walls, fire lines, and plant formations (which grow), in order to creatively contain falling lines of sand. In another, you manipulate a single thread which condemned souls can grab onto (if you let them.) Swing the thread in the right way, and you’ll fling the souls up into heaven.
Both games suffer from the lack of a victory condition and/or point system and/or levels (any one of these would give me more reason to play the game repeatedly over the long term). That said, I really enjoyed the gameplay. It’s a lot of fun experimenting with the tools you’ve been given; seeing what works and what doesn’t.
I can easily imagine versions with interesting victory conditions which lead to progressively more challenging gameplay. For example, level two of the hell game could have a little demon who occassionally skewers the souls you’re trying to rescue. :)