In some games, there are upgrades and level ups that exist to give the player a feeling of growth and accomplishment.
This is not one of those games.
In this game, the player is given a choice, that choice is to choose either speed or agility on level up. Except, I have no idea what that choice does, and it's ultimately meaningless, because you'll end up maxing them out anyway.
But that's not the only problem here. The fish distribution is horribly uneven, which can lead to your fish sticking to the bottom of the level and doing absolutely nothing until something small enough to eat shows up.
The powerups, while generally helpful, occasionally screw you over. Such as the supersize one, which can leave you in a bad place to return to normal size to, or can get you eaten anyway because there are still bigger fish.
If you ever make a sequel, I would recommend keeping every kind of fish at a set, specific size. That way, you know by quick visual reference which ones are good for eating.
The graphics are mediocre and passable, and the music is fine.
What's up with the invisibility power? The fish only scroll from side to side, so does it actually -do- anything? Other than make it harder to see your own fish, of course.
The next game needs;
Divergent evolution with different powers
Power-ups that help
A little less unforgiving on the difficulty.
This isn't a bad game, there are a few execution problems that really hurt it.
Also; getting the supersize power up turns off the invincibility cheat once it ends.