This is a fun game.
The Space Invaders inspiration is clear, but the game has been set up very well. From the bright and colourful UI through to the little noise when a ship dies.
The power up makes the levels go a bit quick, for the jam this means you can get through the whole game in a few minutes. If you decide to more with this, I would say add more levels, or have the power up spawn a bit later in the level.
Thanks for the game.