I enjoy Advent of Code and was inspired by it, but since it runs for a short time each year, I wanted to build something in a similar spirit that people could play year-round.
In Marches & Gnats, you do not write code in a conventional programming language. Instead, you program a single-tape Turing machine by defining its transition rules, running it, and inspecting the tape to see what happened.
There are currently 33 quests. Some are small and can be solved in ~20 minutes, while others are more involved and reward careful planning. The problems cover arithmetic, sorting, parsing text, ciphers, cellular automata, and related topics.
The game also has public leaderboards that focus on solution quality (program size and efficiency), rather than how quickly a solution was submitted. I've also experimented with AI agents that attempt to solve the same quests by directly programming Turing machines under the same constraints.
I would be very interested in feedback, especially from Advent of Code players. Happy to answer any questions!