Flow/Gameplay

Gameplay and design (Flash version)
Both Flow's play structure and aesthetic design are simple and intuitive. The player begins the game as a small, white, worm-like micro-organism on a bright, two-dimensional plane. Using the mouse, the player can guide the worm. Clicking and holding down on the left mouse button accelerates the speed of the worm. The objective of the game is to guide the worm to eat other micro-organisms and evolve. Eating cells increases length, however there are two special cells: one increases mouth size temporarily and the other evolves body segments. While many of these micro-organisms are defenseless, there are certain types of multicellular organisms that will attack the worm. To defeat these enemies, the player must guide the worm to eat the glowing cells that make up the bodies of the enemies. Different types of enemies have different ways of attacking the worm, so the player must determine a particular strategy to defeat each one.

Early on in the game, the worm swims in brighter planes. To progress into darker planes (where more difficult enemies dwell) the worm must eat the red micro-organism. Alternatively, the blue micro-organism enables the player to back-track to brighter planes. These special cells are always present, except on the brightest and darkest planes, where the creature can no longer travel in that specific direction. Players are capable of customizing the physical appearance of their organism based on the gameplay.

There are currently two creatures available to play. The first is the worm phase in which the player's avatar evolves into a multi-segmented worm. If the worm defeats the last, worm-like enemy on the final bottom level, the worm eats a special orange microorganism and floats to the top, is reborn as an infant "jellyfish" creature and the background screen changes from blue to orange. If the jellyfish replays all levels it will return to the surface and begin life again as a worm but not before fighting a boss, which turns out to be the first worm-like creature the player was previously. However, currently there is a bug that renders some players who defeat the boss in jellyfish mode unable to return to the surface.

Gameplay and design (PSN version)
On the PlayStation Network version of Flow, the look and feel of the game is very similar to that of the computer version. There is an increase in the number of items on-screen as compared to the computer game, and the game displays up to 1080p HDTV. The creature is controlled by tilting the controller in the direction that the creature should swim. Pressing any button (except start -- pause, select -- screenshot, or the Playstation button) will cause the creature to use its special ability.

The PS3 version of Flow has several added features, the most obvious being that there are six creatures to play as, all with different abilities. In addition, the player can also eat power-ups which will cause their creature to move faster, and have a bigger mouth to eat more organisms with.

The PS3 version has multiplayer action for up to 4 people. Other players can join in at any time and will be the same type of creature as the first player. With the addition of the addon pack released on November 20, 2007, each player joining in has the ability to choose what creature they wish to be.

Creatures
The player can control six different creatures, all with their own unique abilities. Each creature must eat other organisms to grow bigger so that it can go deeper under water until it finally reaches the bottom area. When the creature eats the ending piece, the game returns to the top so that the player can start over as a new creature.

Once unlocked, the player can play as any of the creatures at will. Midgame, pressing "Start" and eating the blue organism will take the player back to the creature selection area. By eating the creature's egg that the player wishes to use, the game will start over at the newly selected creature's first stage.

The creatures are unlocked in the following order:

Snake
The Snake is the first creature that the player starts with. It starts out as a minuscule organism and as it evolves it becomes greatly longer and grows wing-like flagella on its sides. The snake's special ability is gradually becoming faster.

Jelly
The Jelly is the second creature in Flow. It is very small to begin with, though slightly larger than the Snake. The Jelly's ability to spin in circles very fast causes a suction effect that causes small organisms to become entangled in it. Afterwords, the Jelly becomes dizzy, or stunned. This ability is highly effective in groups of organisms.

Manta
Manta is the third creature in Flow. It is the largest creature in the starting stages and starts out looking similar to a dolphin. It has a similar ability to the Snake. Rather than going faster forever, however, the Manta has short bursts of speed, similar to when dolphins are attacking a group of minnows. These bursts of speed have charges, and the charges appear as its tail. The more evolved the creature becomes, the more charges it will gain, and around midway through the creature's life cycle it will develop flaps, making it look like a Manta ray.

Rogue
The Rogue is another snake-like creature and is the 4th to appear in the game. It has a different, more sinister ability to paralyze its prey. The Rogue's special ability is to cloak itself. While it's cloaked, it will move at a slower pace, but when it bites another creature (e.g. Jelly) the bitten creature will be paralyzed and unable to swim away. As the Rogue evolves, it will grow very large wing-like flaps at its head, similar to a cloak. The rest of the creature's body also gets longer.

Hunter
Hunter is the 5th creature, and again looks like a snake. As it evolves its body begins to look like blades (mostly noticeable when it turns) and like the rest, it gets longer as it grows. Its ability allows it to move very quickly toward a target's weak spots, making it easier to eat them. It signals that it has targeted another creature by turning red.

Puffer
In the add-on pack, there is the a creature known as the Puffer, it is similar to a jelly, but has a different mouth and has blades. Its special ability is to form a shell that nothing can penetrate around it. When the player lets go of the "shell" button, the blades spin outward and can stun other creatures. It cannot keep up its shell forever and when the shell glows red, the creature will automatically do its spin attack. Like the Jelly it gets dizzy afterwards. It grows similarly to the Jelly, but as it evolves, it acquires more blades and can keep up its shell longer. According to a man interviewed in the 11th Annual Interactive Achievement Awards, the Puffer is "All about surprise." He also stated that the Puffer would become very aggressive and become more offensive to the opposing creature.

Credit Creature
The Credit Creature is very similar to the first Snake, with few differences. It has the same ability as the Snake but its body grows very much longer than the Snake's maximum length. It does not grow wing-like flaps on the side like the first Snake does. There are no enemies in this creature's environment, rather, it just swims around and eats the food that is next to the credits. When it reaches end of the credits and eats the final egg, the game will return to the top and the player starts over as the Snake again.