Here's some feedback that in my opinion could be beneficial for this game and wouldn't take too much time:
- Incrementing the fire rate of the player
- Once the fire rate has been incremented, you could increment the enemy speed and make some of them move randomly
- Add some limits/colliders so that the player can't go outside the screen.
- Some type of score/time counter that encourages the player to survive longer.
Having said that, considering this is your first jam and you had one week of time, its a good game. Great job and keep making videogames!