im thinking of making a game, but i think it may be a bit time-consuming, so i was wondering if i could make sprites and textures right now, and use them when im making my game.
part 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
This means that using pre-made assets is allowed. What the other user also said, it might take away from your jam experience to prepare assets in advance. It's also going to be hard to create your sprites etc. in advance, as you don't know the theme yet. I hope I answered your questions, let me know if you have any more!
