Stabfish.io is based on the idea that players are not only competing against each other but also against the environment. The more you kill, the more resources you gain to help your weapon and armor improve. It is similar to Cuphead.
There is also a survival game where it’s just you versus other players. You will have to survive as long as possible in many different environments and fight off other players. In particular, you can upgrade your character and weapons after eliminating each opponent. You can see this feature in Smash Karts.
Slide your mouse to move your fish. Click the left mouse button to speed up. Control and use your weapon to attack your enemies to kill them. It is easier than Cuphead because of the one-button controls of this fighting game. You don't need to use other buttons to play.