If you're interested in the math behind the first-person rendering algorithm, this tutorial was incredibly helpful: https://lodev.org/cgtutor/raycasting....

00:00 - Intro
00:46 - Basic Game
04:27 - More Mazes, Bigger Mazes
06:26 - Map List
07:56 - Non-linear Map List
11:10 - Colors
12:40 - Renderer
15:17 - Final Game