Aritm is a game that trains you in mental calculation. It only teaches what is necessary to know in order to calculate manually using pen and paper. It adapts and asks more about what you answered wrong before.
Aritm is written in pure Commander X16 BASIC v2 and uses X16 control codes for text and screen colors, and has sound effects.
Future versions will probably support larger text in game.
Aritm is available for many platforms including graphing calculators, Java phones, spread sheets, and common retro computers.
You can run using the "Try it now" button or from command line:
x16emu -prg ARITM-X16.PRG -run -echo
If you exit the program you can LIST it and copy the listing to an editor.
Aritm is open source (GPLv3) and is tested using an automatic testing system: https://github.com/mobluse/aritmjs