I've just started adding an in-game menu. Making the state-machine was surprisingly easy to pull out with the architecture of the game engine. It should be pretty smooth sailing from here to allow me to reuse code while still keeping the gameplay and editor separate.
New Textures and Simple UI Buttons
I added a different texture pack to start from. Still not my own textures but it'll serve as a base point for a while as we slowly start making our own textures. Also added a way to easily add buttons to the UI. I went with a method proposed by Casey Muratori called "Immediate Mode GUI" (https://www.youtube.com/watch?v=Z1qyvQsjK5Y). It was surprisingly easy to implement.