Another browser based thing I was working on but never went very far with before returning to focusing on Wii homebrew was a game called Maze Slugs. It was a top down shooter similar to They Do Not Die but obviously browser based. As the name suggested it also uses randomly generated mazes instead of pre made maps. I didn’t get very much done before growing bored with it. You can move and shoot but it has no effect on the enemies and they have no effect on you. A lot about how it was written is sloppy and just slow. Still it might be somewhat useful if you want to read an example of how to generate mazes in Java Script and it should be fairly easy to adapt that to any other language.
Something else worth ignoring