Hammurabi

Note: the current iteration seems broken both online and playing through Gargoyle. I thoughtlessly typed 'help' as my first command and led me into a (bug) cycle I couldn't escape.

Hammurabi wants whole, positive numbers only.

I remember when this came out (the Hugo port, that is), and enjoyed it. It's a different thing than the usual IF, and these days I could see it being a good base for a mini-game or something within a larger work.