The soundtrack is awesome :)
And with that in my ears, I would have loved to get on the leaderboard, but the problem is well known.
I always like having multiple skins, but I would like it even better if the skins were connected with added value. So that each skin offers the player a different added value (better shield, better movement, more points per 10 seconds...).
Recharging the shield would also be conceivable.
Further improvements:
Darken the background with its stars a little (the bullets should be more visible than the background). Perhaps planets could also be integrated and adding a parallax effect might give the whole thing a nice depth. In the same vein, the power-ups in space could also be given a little movement!
Small bug: The shield was not centered correctly for me.
Overall, thank you very much for this hour of gaming fun. I really enjoyed it!