Just try and come up with some cool and unique ideas to put into your game along with the combat. Maybe try and mix game concepts you've seen before. Go crazy. I actually don't know why I'm trying to help you, I am your worst nightmare.

Also, any theme can be made into your platformer. You want horror, sadness, the fear of never getting out? As long as it's interesting. 

Your platformer doesn't need to have a story it's optional, just make it interesting. 

Any game engine is allowed, just make it interesting. 

If you really don't have experience making games, I have to say, you are the most stupid person I've ever met. Who enters a game jam new to the concept of code? But nonetheless. If you feel that you REALLY need a tutorial, I'm not stopping you. But don't use it for everything, you gotta learn something from this right?

Also please don't feel pressured if you enter, this is for fun! And if you lose, everyone in society will hate you! Your whole life will collapse slowly as you watch your demise! Remember everything you used to have know and love? It's all gone! And all because you lost that game jam! Gosh diddly darn! I guess I'll go for 2nd place next time!

Seriously though, don't beat yourself up over it. And if you lose,  it just makes you a better game designer. So maybe you want to lose? I don't know!

I seriously forgot to mention, the prize is a surprize. SO DO IT!! IT MAY NOT EVEN BE WORTH IT BUT DO IT!!