Mazified was originally made as a school project for my CS class, but has since expanded way past that.
Coded entirely in Java with JFrame. I would have saved myself over 100 hours of pain if I had used an actual game engine (rip).
If I had to say what was the worst part of making this, it would by far be the network code. It's not even close.
My favorite part was writing the game logic system itself.