Maths!

I am sitting in front of the computer, and I will write a lengthier, additional post, but first I have a question:

If you are/were a math teacher or know someone who is/was, or if you are/were a student in a math class: Would you mind sharing any math games or activities with me? Preferably ones that require no materials, or at least not materials for which I can find no substitute in The Gambia. For example, Buzz! is a great game to practice multiples that until recently I'd completely forgotten. The games/activities could be for topics like fractions, negative numbers, factors, simple linear equations...

Thanks!