Thanks for checking it out! It is incredibly simple and I was really pressed for time and really rusty with XNA/MonoGame when I signed up for this. I've spent so much time in the past making very large complicated games and never finishing them. So I figured I'd try and actually finish some smaller projects and publish them. Having a game jam deadline was good for that, but I had to scale it way back to get it finished.
To the question about MonoGame, it is quite a bit different from Unity, but is also a great way to build games using C# (I may be biased though as I am a contributor who helps work on it now) . Unity is a full featured commercially viable game engine, while MonoGame is an Open Source low-level game development framework. It is a re-implementation of Microsoft's XNA game framework from the 2000s that they ended support for in 2013. Basically, MonoGame is a programmer first way of making games without an editor or pre-built engine. You build the game engine yourself and can either create it all in code, make your own editor, or use a third party editor like Tiled or Ldtk and integrate it with your game code. MonoGame is an abstraction layer that sits above the underlying graphics and input APIs like SDL/Open GL and DirectX. It gives you a way to manage frames (Update just like in Unity), and a way to draw every frame as well (SpriteBatch). There is also a built in content pipeline for loading and working with your assets, and a useful Math library that is optimized for use in games. I work as a programmer in my day job and C# is one of my more proficient languages, so it's a good fit for me. It means I spend less time learning how to use the Editor and more time just building what I want to build. It has some downsides though like it is much harder to get started with, and you literally have to build everything so it's not for everybody! I started doing some hobbyist game dev with XNA back when I was in High School and College, and then I switched to Unity when Microsoft ended support for XNA in 2013. I've spent the last few years using Unity to build a bunch of complicated 3D games with low-poly assets that I never finished or released. Finally decided last year to go back to my roots, get a bit more serious, do simpler 2D games, and push myself to finish somethings. Making myself publish them whether I think they're good enough or not.
I have some more interesting games in the works and one of them (albeit a simple puzzle game) should be releasing soon (finishing up some of the final music and artwork for it). The puzzle game takes some of the learnings I had from this like adding a shader, full screen capability, and using better techniques to scale pixel art assets. In it I challenged myself to create something where I did all of the artwork, music, and of course built the game-engine, whereas this game I did a mix of off the shelf stuff and some of my own work. So it will be simple too, but I learned a lot from it (like how bad I really am at art, and how I should rely on others for that lol). And I've already started the next two games I'll be making after that. Both also pushing me to do some things I haven't done yet, or that I want to learn more about.