You are the goldfish.
Use the arrow keys to move the goldfish around to eat other fish.
You can only eat the fish that are smaller than you are.
With every level you get bigger, so you can eat more fish.
In Level 1, you can eat the little red fish.
In Level 2, you can also eat the red-yellow fish, which give you more points.
In Level 3, you can eat the purple fish as well, which give you even more points.
Don't forget that if you can't eat the fish, they can eat you. When you get eaten you lose a life.