Personally, I like to play video games from time to time, especially arcade games (e.g. Tetris, pinball) or fast-paced games like Super Hexagon, which is known to be quite challenging.
However, for mathematics (that is not intended for kids) I have not found anything interesting so far.
What I am thinking about is a game where one has to do (increasingly difficult) calculus under a time constraints, with perhaps a 'health bar' that increase or decreases depending on how you are doing. Perhaps with music, nice visuals or other such things.
Does someone have a suggestion along these lines?
Also, I did find this related but otherwise very different question: Is there any gamified software for learning advanced mathematics?