Nice concept, but initially I tried to go up to hit the spaceship: it wasn't clear to me the goal was just to survive (which is very hard). :)

You could expand your concept further in the future, for example by letting the player move a whole group of invaders instead of just one. :)

Very challenging game! I included it in my compilation video series of all of the GBJam 5 games, if you'd like to take a look :)