You would be excused if you thought this were just another of those Darwinian games, similar to flOw. Gobble up certain primordial creatures while avoiding other predators.

Osmos owes more to Newton than it does to Darwin. Certainly you do absorb other single cell organisms in the primordial goop, but it is the constant conisderation of Newtonian physics in the game play that sets Osmos apart from similar titles.

Economy of motion is at the heart of the gameplay.

The goal is to grow larger by absorbing other cell structures. Larger cells absorb smaller cells. If your cell runs into a larger cell, it is game over. If you run into a smaller cell, it is absorbed and you grow larger. Collisions between cells other than you own behave by the same rules, absorb or be absorbed. A cell you're hoping to absorb might suddenly be off-limits if it collides with another cell before you can reach it. The game keys you into cells you can absorb versus cells that will absorb you using a simple colour coding. Blue is safe. Red is danger.

Movement is exceptionally simple. Tap the screen. Where you tap, your cell will add some small amount of velocity in the opposite direction. The quicker you tap, the more velocity added.

The game opens with the following quote: "For every action, there is an equal and opposite reaction." That statement by Newton is at the heart of the strategy in this game. The trick, the Newtonian piece of this puzzle, is that whenever you move, you shed some small amount of mass in the opposite direction. Move to the right, shed mass to the left. Zipping around the primordial playing field will have your cell shedding so much mass so quickly, that soon there will be no cells smaller than your cell to absorb. Careful planning in every movement is required.

This is a game of patience, moving about as quickly as possible is not the goal, and could be a detriment to your cell's survival. That said, sometimes you'll be moving so slowly that it will try your patience. The game accommodates for this by allowing you to increase and decrease the flow of time. If things are becoming too crowded, too hectic, and you need time to figure out how to get out of a dangerous situation, a quick swipe to the left will slow down time, giving you those extra moments required for decision making. If you're in no immediate danger, a quick swipe to the right will speed up the passage of time.

This is a game about gobbling up your neighbours, but it is also a game about economy of motion.

For every action, there is an equal and opposite reaction.

There are two basic playfields. The first is a simple playfield where you freely move about without any outside forces affecting your vector — your speed and direction. The second consists of one or more gravitational bodies which have a constant effect on your vector of motion. Further complicating the challenges are cells with their own unique properties. Some are attractors. Some are repulsors. Some will evade or hunt you depending upon their relative size to your cell. All cells play by the same rules; when they initiate their own changes in velocity, they too shed mass. Chase an evasive cell and pick up the mass it sheds in its wake.

There are a myriad of strategies involved in the game which makes each of the challenges unique and offers a lot of replayability. Along with the ongoing challenge mode, there is an arcade mode, and a multiplayer mode.

The game is published by Hemisphere Games and is available for iOS and Android. There are also PC, Mac, and Linux versions, but the game seems much more suitable to mobile play than desktop.