If I make an inventory system and do most of the art for my game ahead of time.
I want to compete solo and art takes me a long time, it is cool if I do these things ahead of time?
Sorry, the production of the game should take place during the week.
The rules mention you can use premade assets and preexisting code, but the rationale is that these exist for reasons other than the game you are going to create.
You can always cheat and say you are making a generic lib that you will then use for your game, but that will take away the fun of the challenge.