Ren'Py

Tom Rothamel started Ren'Py in 2004. A game is written like a screenplay: e "Hello." shows a line from the character e, show and scene change the images, menu offers the player a choice. When that isn't enough, ordinary Python can be embedded straight into the script, while the engine handles saves, dialogue rollback and translations.

Ren'Py long ran on Pygame, later on its own fork of it over SDL. By lowering the bar until a writer with no programming background could ship a game, it became the genre's de facto standard in the West. Doki Doki Literature Club (2017) is the best-known example, and part of its horror comes from the game tampering with its own files while you play.