When I am not busy at work or rearing four kids, I like to take some time to play Fantastic Contraption. Here is the idea:
You are given five objects. A wheel that rotates clock-wise, one that rotates counter-clockwise, and one that is neutral. You also have a solid rod and a liquid rod. Nothing can pass through the solid rod while most objects can pass through the liquid rod. You also have a construction area, a goal area and a goal object. You simply try to get the goal object (a ball or square or combinations) into the goal.
The best part is that you can pay a one-time $10 fee and design your own levels and play other people designs.
Hope this wastes a lot of time for you, because this is pretty fantastic.
And so it goes.