Tile-based Collision Detection and Correction is working!
I managed to implement a system for all Entity objects that allows them to correct their position so they don't pass through walls.
I've also added a thing so that the 'camera' want to center on the middle of the dungeon, but will move when the player gets too close to the sides of the screen.
I think I'll try to implement an attack animation for the player next. After that, I'm thinking I'll be making my first baddie.