God Tower is a very difficult puzzle game. Each level presents you with an image, and the point of the game is to guess the riddle that the picture presents. You input the answer to the riddle ( all lowercase one word), and then you proceed to the next level. I only had enough patience to get to level five (with a hint on level 3.)
I learned about God Tower from jay is games. Jay runs a fantastic blog about web games and game design. If you’re looking for something to burn some extra time, jay is games is a good place to start.
I second the "very difficult" part. I’m not sure why the game instructions are in Thai, but it certainly increases the learning curve. The game is both fun and very frustrating. Don’t go if you don’t have time to kill!