Great game from the past
One thing that always annoyed me was the health pickups at the end of a level. I kinda understand if you don't want to activate a spike ball or you already have a nuke saved, but health? Just give it to me! You can still use it as a reward for finishing a wave, but just have it automatically come to me; it annoys me when low-skill stuff isn't just automatic. This would also solve the problem of accidentally clicking on yourself and attracting a ship, because there would be no point in being able to select yourself anymore.
That and i instinctively want to click on empty space to deselect a ship, but that doesn't work. It does make the game harder though, which is a good thing!