Wish Upon A Star
Wish Upon A Star is an online moderated board game I've been hosting on and off for ten years. The basic premise is simple. Everbody starts on the start space, players can move five spaces per turn, and whoever collects the most gold coins wins the game.
However, all of this changes, due to the presence of the Altar. When a player arrives at the Altar, which is a space that's always present on the board, they can make a wish to change the game's mechanics or the shape of the board in some way. There are a few common sense restrictions, but outside of that, anything within reason can be wished for, which makes the game self-modifying.
Players have taken this game in some very creative directions. In the past, we've made the board three-dimensional, sent players to the past and future, summoned mystical genies, simulated Conway's Game of Life, and even implemented a working lighting engine for a fog-of-war variant.
The interactive board for Wish Upon A Star is currently hosted on my old website, where you can also find some more of the history and rules of the game, as well as some of the more complex wishes that have been made.
The rendering program used to generate the game board images, as well as the metadata for the interactive board, is available on GitHub. This renderer is also capable of computing lighting in three dimensions and can handle a variety of Conway-style spreading mechanics for terrain and elemental spaces.