- Any mechanics.
- Code - it's appreciated that it's yours and that the game was written from scratch - (in my opinion it's the whole point of game jams unless it's specified that any code can be used). You can use other code, but you have to write what parts are not yours.
- If you work without artist It's OK to use assets (remember to give credits, also specify even if they are CC0).
I want to add one thing, don't be scared if your modeling or anything like that isn't as good as you would like. Sometimes even bad graphics give very good feel of the game, it's own style - just say that you planned it to look like this :). I encourage you to create everything on your own, It's a lot more pleasure in the end when you created everything on your own - doesn't matter how it looks!
Point of game jams are to develop yourself and find your weaknesses, also to have a lot of fun :).
I hope with every new jam you will be more skilled in code or modeling or anything that is about game development and more.
That was my bad not to specify things like code and modeling in the description and I promise I will fix this on the next game jam. Now I'm going to edit description of this jam about these questions. Also I will add criterias of voting.