After considering many different types of variables to use, I settled on 64-bit fixed point numbers. These numbers are stable for all integers in their range, yet give you three decimal places. I wanted you to be able to have decimal point numbers so you could do the math you need for things like ring menus, smooth movement, etc. but still be able to use them to index arrays or IDs. Floating point numbers can do strange things when being converted into integers as they reach larger values, and they're slower to work with than integers.

This trick had been done on 32-bit numbers with three decimal places accuracy, but it limits you to numbers of about 2 million in either direction (positive numbers and negative numbers). I've commonly run into problems with this limit when trying to write RPG systems on 32-bit fixed point variable game engines (like old versions of ACKNEX and WDL script). Using 64-bit fixed point numbers gives you an insane limit you could probably count the stars in our galaxy with. I think it will do for an arbitrary RPG game.