Software, GameDev, Photo...
GoldSrc engine (Half-Life, Counter-Strike 1.6) re-implemented with Vulkan as its rendering engine.
I have grown up with Counter-Strike (my first nickname was created in about 1 minute as I needed it for small LAN party), I later discovered Half-Life itself and even Valve Hammer Editor (AFAIK none was hosted on any server), diving deeper into the game/engine was, at least for me, natural.
It all started by looking around for documentation on BSP/WAD files. Found one project called hlbsp with good-enough documentation.