Our second game project was based around symbiosis, cooperation. So we made a co-op game!
Since we were making a 2-player game we needed simultaneous two player input. I made a system where you could play either using 2 gamepads or 1 keyboard + 1 gamepad, and the players get to choose individually how they want to play it.
I created a lot of prefabs for the puzzles and triggers for the designers to play around with.