Tried the game.
Cool game, although the guns and the crab do not really fit into the art style.
I'd suggest sticking to a simple colour pallete. For my game, I chose only about 7 colours. In case of your game, I could count up to 16 colours.
I'd also suggest never using black. Use a really dark shade of any colour. Really dark purple always worked for me.
And, don't outline too much. (you can, but you don't have to)
Here's a helpful video about what you should avoid while making pixel art
(You probably used some free assets, but it's still always good to learn something new, because you might use it later, maybe for another game jam)