TubeTwist is an interesting game. I've only played the demo so far, but I really like it. It's one of those games where you have to deliver a ball from X to Y using various forms of tubes. It's like TIM except that you only have balls and tubes.
The game even has a story, not a very useful story but it kinda makes sense.
The demo only has 6 levels, the full game has 80. It took me some while to complete those 6. It's a great game to simply play when you have some spare time. The demo has one annoying bug and that is that it doesn't work very well with a multi monitor setup. If it's fixed in the full version I'm going to buy it.