For the actual inner workings of that map: it was relatively simple. I had 2 raw images on top of each other, 1 being a render texture connected to a camera that views the whole map, and the other being a texture that I erased parts of with a script. I converted the players position from world space to coordinates on that texture, and then erased the pixels in a 7x7 square centered on the player.
I thought about how I was going to do this for a while in a break I took mid-jam, then outlined in my head the process I was going to take, and I sorta just started programming and it eventually worked. Making that map took up a lot of my time, I'd say around an hour or so. It might be worth noting that I did a whole lot of things to try and maximize my time developing things unique to this game (like I started from a template project I made a while ago that already had a basic main menu scene, and repurposed a bunch of scripts and assets from previous projects) and that definitely helped. However, I don't think I will do that for next jam as in this jam the map was pretty much the only thing I needed to code something entirely new for.
I hope that helped.