Wow, this game is really fun! It took me a couple tries, but I started to understand the mechanics of the multiple bullets and how to destroy the rockets. For me, I love games that allow me to find the answers on my own but I feel that you could've put in a small "How to play" on your splash page for others who might be struggling.
In terms of other feedback, I would say to indicate the line where rockets will end up exploding on the screen. The line didn't seem to be as low as I would've though the first time around and it's hard to tell which rocket to destroy first because I can't visually see which is the closest when there is eventually too many rockets on screen. As a player, I need that information.
For your first game jam, this is an amazing start. Love the mechanic and how intuitive it is. Keep it up!