And it is released for these platforms Microsoft Windows,macOS, Linux.

flOw, by ThatGameCompany for PS3, also a Flash game: You start as what is apparently a fish, that eats things, to become bigger fish which help you eat the eat fish that tried / try to eat you. Feed and Grow: Fish is a brand-new animal survival simulation PC game developed.

Katamari Damacy - the objects that you're aggregating do not fight back, and you win at a certain maximum size.

Osmos with plenty of passive targets, but a branch has opponents that are active players.

Mope.io takes this more literally by using animals.

They are available online in the browser and have some power-ups as well (splitting your amoeba on demand for example).

Agar.io and Slither.io (multiplayer) are multiplayer games of this type - in Agar.io you control blobs/amoebas and in Slither.io you control snakes.

See also Muscles Are Meaningful and Miracle-Gro Monster. Note that you must only be able to defeat creatures smaller than you, most of the time (not counting power-ups).

What platforms is feed and grow fish on