I still love Cosmic Osmo for what it is, even all these years later. It's not much of a game, much closer to a "toy", you play with it, but it doesn't really have anything that defines it as a game by modern standards; There is no winning or losing, there are no time limits, there are no objectives. You wander around neat places, interact with silly stuff, play with things you find, et cetera.
And, being a Cyan game, Cosmic Osmo shows that they have beautifully detailed and expressive art design, even in straight-up black and white. Damn! Look at those monochomatic pixels, they're great!
This is a great game for kids if you need to keep them entertained for a while, also good for grown-up kids who want to unwind to a game with zero expectations and a lot of content/hidden fun for you to discover.
Since this game cannot be purchased on its own, I can only tell you whether or not it is a worthwhile addition to the Cyan Collection:Hell yes it is.