There's a certain Atari-like charm and an interesting gameplay loop idea to this game, but imo it needs some polish. During the shmup section of the game, some of the little enemies are liable to almost teleport in front of you. I also had to maximise the window because some stuff, like coins, were hard to identify at first? I thought they were enemy shots.
The cave is an interesting concept, I just wish that the controls weren't divided between mouse and keyboard. Fortunately, the keyboard controls are pleasingly simple so it's not too much of a dissonance.