I recently found a very simple, yet challenging game called Taxman. The principle is pretty simple:
- you get a grid of numbers from 1 to X (min. 20 usually)
- when you take a number, the taxman gets all the remaining factors of that number
- the picked number must give the taxman at least one new number.
- when you can't move any more, the taxman gets all the remaining numbers
- the goal is to collect more then Taxman (the sum of picked numbers)
Here is the original link as an example: http://davidbau.com/taxman/ in <iframe> bellow.
Credits for the code goes to David Bau, http://davidbau.com/
If you get frustrated go for the explanations here: http://mathdl.maa.org/images/upload_library/22/Evans/Horizons-Feb07-p18-20.pdf