Check the rules on the Overview page:
"The only rule we have is that your game must not include any NSFW and offensive/discriminatory content. We wish for the games to be playable by everyone!
Apart from that you are allowed to use any game engine or framework, you can also use assets not made by you, but make sure you have the proper license to use them and crediting is of course encouraged! Making everything from scratch is not mandatory, but if you do you get to be extra proud of yourself at the end!"