Physics engines are so much fun to play with. Just had a first project based #gamedev session with a new student, and went from zero to a player controlled #godot block bouncing around and bashing evil red godot faces out of the way - all in under an hour.
And there's just so much built in entertainment from what you're working with. Most (not all) bugs are just randomly funny rather than deeply frustrating - watching the player drop off the screen because there's no floor, firing them out of view because you typed an extra zero, etc...