Hi John! played your game for some time :) Here is my short review, tried to be aligned with your request of features that need to be improved:
First of all, I think you should consider to improving your sprites. Mainly the monsters - try to add more details to the face. Also maybe add some idle animation? for example the monsters mouth open and closes, or the spaceship engines buzzing.
Regarding the backgrounds transition, maybe make those more slick - instead of the flickering maybe make the movement more continuous - as in the opening screen.
Another minor issue is that the monster can be created on the player, which cause the spaceship to crash automatically :)
Anyway nice game, really loved the music!
Hope this review was helpful :)
Shifful Studio
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