Desktop gadget (Windows only). The simulation of a real horizontal sundial, dependent on a geographic position (latitude). Size can be chosen between big and small. It can use current (computer) time, or user-specified date&time.
A shareware game called begin was released in 1984: a tactical starship game with a good AI and fair rules (the computer had no advantage) I've hacked assembly code to make it a multiplayer game, so that folk can challenge each other rather than the AI.
Real-time collision detection library for physical simulations in virtual environments. Includes support for self colliding objects as needed for simulation of textiles and clothes.