I've been playing around with various procedural generation techniques and wrote a little tool for creating generative string grammars. It's 104 tokens and the code is on github under an MIT license.
Demos
This first one generates side-scroller/platformer levels. Each character of the generated string represent a four tile wide column of the map. I didn't add a player because I just wanted to showcase the level generation itself so the map just scrolls automatically from the start to the end. Reload the cart to generate a new level. It's just an example so the levels aren't particularly interesting but you could add a few "post-production" passes over the generated strings to clean things up, generate enemies, add additional rules for pre-made features, etc.
I am going to work on this. Later I will remake this with actual line intersection code for raycast hits and vector objects. For now this is just a little 1D raymarching program that is a bit sluggish and uses the map for checking ray hits.
But this is what it would look like living in a 2D universe. You would see a 1D image. I will later remake this, probably in Godot engine, as a high resolution stereoscopic 2D VR adventure game.

Today I am thinking of a game called Pop'n Music Pico 8 edition. It's just like Pop'n music GB, but with more techniques.
Here are some characters that need to be in the game.
Akane [LT] (2P)
Alicia [19]
Alice [9]
Aloe [13]
ALT 2.0 [20]
Arisa [SP]
Ash [8]
Black [LT]
Canopus [SP]
Cherumin [Usa]
Dino [20]
Fuga [pe]
Fukagawa Funawo [12]
Guwanzesama [portable 2]
Harpya [LT]
? (Hatena)[15]
Hiumi [LT]
Jin [ec]
Kanta [13] (2P)
Kicoro [18]
Kobozu [19]
Kojirou [16]
Leicars [7]
Lill [Usa]
Micchan [SP]
Mikoko [12]
Milk [8]
Mimi [LT]
Nyami [LT]
Minit's [SP]
Miyu [LT] (2P)
Mutsuki [14]
MZD [20]
Navi [Usa]
Nia [LT]
Toa [LT]
Nornir [pe] 2P
Oni-Be [13] (2P)
Paku [20]
Pino [13]
Pochiko [SP]
Poet