Wait, there is a store?
Now that you said I looked for it, it is a dropdown menu in the start screen right? it is pretty hard to see. Now that I know that there are more ships, I don’t think that you need to change the speed of the first ship, it is OK the way it is. But perhaps it would be a good idea to make that menu easier to see.
The alien ship has two lifes? I think that the player will just avoid it instead of trying to destroy it, but this is just my opinion,
Another thing that happened to me a couple of times is that I tried to press the shot button but I missed it, perhaps if it was a little bit bigger it would be better (you don’t have to increase the size of the sprite, perhaps just the hitbox), but again, that is just my opinion, I’m a Shrek-sized person with a Shrek-sized finger, I usually miss even the letters when I’m typing in my cellphone