It is pretty obvious that the weapon downgrade needs fixing. It is also obvious that the maker of this game does not give a hoot about improving it. Get off your high horse, take some suggestions to heart and fix this game. It has potential, it just needs some polishing.
This game can be difficult but not impossible. Firstly, learn to dodge and evade. Also, I find the rocket gun -fully upgraded- to be the best weapon. It is also essential to upgrade player stats as well. Speed, armor and bombs can make a difference. When setting off bombs, move across the screen to increase the area of the explosion. This does of course come at the expense of sustaining damage. More enemies appear as time passes, so do not use the bombs too early in the game. My only complaint is that there is no weapon type indicator. That is to say, it is difficult to figure out which weapon is being used. Changing the shape of the ship is of no help, especially when many look quite similar.