Some may have mentioned it but the game needs checkpoints and not force players to start over.
Starting over a stage is one thing but restarting the game for losing all lives is another.
The "limited lives before game over" format is a relic of the past from arcade days.
There's no need for them to be around today.
I only got to stage 3 and because of this formatting, I can't be bothered to redo everything and upgrade my gun all over again just to see the rest of the game.
I haven't tried all the guns but it's creative to have different guns that with different effects, such as the shrink ray.
But I guess things got a little imbalanced when the shrink ray can be used to defeat everything with one shot.
I managed to upgrade my gun to maximum, so the shrink ray recharges quite fast.
I also dislike side-scrolling shooters where you can only shoot left or right.
Might be fun 30 years ago but not something I'd ask for in the current generation.