There is a fish that can eat smaller fish. But this fish may be devoured in the jaws of one bigger, unless it eats many small fish, growing so it may gulp its predator. This is a game about that.

Osmos HD is an iPad port of recent PC/Mac/Linux game Osmos, modified for touch-screen controls. It is a game that won't look to you to be about fish — maybe water globules or stars, osmosis or cosmology. But it's all about "eat or be eaten."

The gameplay is descendant from Pac-Man. You control one circular mote set amid others in a confined playing field. Any contact you make with larger globules is fatal. Propelling your globule into contact with smaller ones lets you absorb them. As you absorb the smaller ones, you grow big, big enough to now absorb what used to be fatal. Sometimes you're in a rectangular arena full of other blobs. Sometimes you're all in orbit around a central body that exerts gravitational pull. You're always eating; you're always avoiding the hunt. Thanks to dreamy music and graphics that have lava-lamp hypnotic smoothness, you play this game in a trance. Best use of an iPad for gaming yet?

Loved

The Subtle Risk Of It All: On the iPad, you propel your little blue droplet with taps of your finger. Each tap made behind the droplet jets it away from that point. One tap barely moves it. Many taps shoots it across the screen. But each tap, big or small, ejects mass from the droplet, making your "character," the droplet/mote/cosmic-body smaller. This ingenious mechanic punishes rash movements. Imagine, for example, you see a smaller blog you want to fly over and absorb. Jetting over there too aggressively will cost you so much mass that you'll be smaller than that other blob by the time you get there, plunging your droplet into Game Over. Should you happen to steer and survive, you still have to deal with what you ejected during the propulsion… your trail of propellant possibly shooting into another blob, making it bigger and more of a threat to you. Or maybe your propellant will ricochet off a wall into itself and coalesce into its own blob. Your aggression breeds your problems. Your ability to calm down and move carefully is always best rewarded. I appreciated the iPad version's option to speed up and slow down the flow of time with the flick of your finger. Very helpful for precise control.

Interactive Art: In some levels you will start in a field of mostly red globules, so densely packed you might as well be a teardrop on red bubble wrap. Red globules are bigger. Blue are smaller. As you slowly find prey and grow, red will drain from the bodies of globules that are suddenly not much bigger than you. As you grow, they re-shade to blue. This is one of the purest and most beautiful demonstrations I've ever seen of the re-balancing of power in a video game. Many games make you feel gradually empowered. How lovely it is to see that conveyed here with a simple change in the colors of the enemies. Turn that field of red globs blue as you grow to be the biggest.

Just Enough Variation: Osmos HD has a couple-dozen main levels and then some increasingly-difficult iterations of the game types introduced in that campaign. Sometimes your level will involve a need to become the biggest in the playing field. Other times the goal will be to absorb globs that try to flee from you, or to ride the orbit of several star-like objects while not falling into their gravitational pull. The main gameplay mechanic is so pure in Osmos HD that even these variations are more than enough.

Watch a movie of Osmos HD — perhaps this one made by the developers — and imagine your fingertips nudging one drop of water or cosmos or whatever into dominance. Imagine being the biggest fish by outgrowing your predators and doing that will sometimes spooky, sometimes ethereal music plays in the background. This game may look like Pac-Man or Flow; it actually plays like a next-level Katamari Damacy in which the small objects you can pick up may themselves coalesce into a mass that could roll you up. This game is pure gameplay, something you haven't done before, can't imagine in any other medium. Justify your iPad purchase and play it.

Osmos HD was developed and published by Hemisphere Games on July 10 for the Apple iPad. Retails for $4.99 USD. A copy of the game was given to us by the publisher for reviewing purposes. Played through the campaign and several of the "arcade mode" variations.