Try cutting down on scope. The idea is good and could be implemented in a great way, but for now, try having just one type of enemy, and make the assets like art and music very basic. You could download assets online if you credit them. When i got my game idea, i had a huge scope in mind but i had to cut down on a LOT of stuff. Just make the game really small for now, and you can expand on it in the future after the game jam if you want