Yet Another MOBA (In 13kb of JavaScript)

For the third year in a row, I participated in JS13k 2021, where you're tasked with making a game in 13kB of JavaScript. Each year I enter participate I try to learn something new I didn't know how to do before. This year's motivation: I wanted to make a multiplayer game with some nontrivial networking aspects. So below you'll find a description of my experience building a MOBA in (barely) under 13kB of JavaScript.