Really fun little game, I didnt think i'd be playing this for as long as I did.
First of all the graphics are cute, the tune is chipper, the fact that there is more makes it less repetitive, the ink spewing to hold enemies back, and the fact that your ink meter is your own saturation is amazing imo, neat little detail.
The fact that multiple colored and styled walls are used makes the navigation easier.
The power-up only killing one fish is a bit meh, I did miss a rampage where i could just headbutt all the fishes, but the fact that you can play basically bowling with the fishes, by hitting one into another kinda makes up for it.
But I do think that the game is a bit bland. Every level is basically the same. Eat shrimpos (the chaining mechanic is nice) and kill fishes. I would have liked to see different powerups per level (where you shoot something else than ink or gives you different abilities , different enemies, or just really anything that gives you a reason to play. Currently, once you played the first level you saw everything that the game has to offer.
But these added things most probably detract from the type of old school arcade game feel that you are going for, and made really well!