Hi Kurre, and welcome to the forum.

I was brave enough to try it out, but I wouldn't recommend anyone nowadays to download and run an "exe" file - it could be a virus, spyware or simply do nasty things to your computer. I am not saying YOU would, but it is just a principle OK?

Having got THAT out of the way - it looks like a good idea. The decreasing time bar sure put me under pressure.

You could have different difficulty levels, from single digit addition to multi-digit division. Even some algebra or word-based problems ("two trains are travelling ..." style)

But for the internet, don't use "exe"s try Java, Javascript or Flash.

I enjoy using SwishMax, which is a Flash development tool, they have a 15-day trial I think. If you like it then it is about $US 100 to buy, or you can buy Flash 8 Professional from Macromedia for $US 700. Your choice.