make some stuff you can't shoot down, will damage your plane/gun for a second or so. now its constant shooting and moving left to right to left. make some background, on 2-3 different underlaying layer and move down with parallax. this would increase your overall graphic quality a lot with only 5 minute work. all in all nice game. since I made my game in costruct too, an explanation on how to let this run on a page would be welcome to a brand new construct man :).
feel free to try-out and rate my game.
https://itch.io/jam/blackthornprodgamejam2/rate/379449
Kris