I have seen the "world" of flOw referred to as a "biosphere" or a "universe," but it appears to me that flOw actually takes place on a microscope slide.

The graphics in flOw are absolutely beautiful, as you can see in the screenshots. The organisms themselves have very simple designs, and the color palette used is nearly monochromatic, with occasional flashes of color indicating that an organism is becoming aggressive or is being injured.

The sound effects are composed primarily of simple tones that ring out when you consume a smaller organism, attack something or get attacked yourself. These simplistic sound effects are at differing pitches, however, keeping the game from being too repetitive or aggravating and, in fact, are quite relaxing, much like listening to wind chimes. This was a refreshing change of pace from the typical blood-pumping musical assault that most games feature.

In flOw, you control a very simple organism that can swim around in a circular area and interact with other organisms. The twist here is that, as they say, "You are what you eat." That is, each time you consume another organism, you not only get a meal, but your organism evolves and becomes a larger, more complex organism. Furthermore, your health is indicated by the number of body parts that are brightly lit up; each time you are injured, another section of your creature goes from a bright white color to a dimly lit greyish-white pallor. To regain health, you'll need to consume more simple organisms.

While flOw has all the necessary elements to be a game, it is a very simple game and tends to be more about exploration, making it feel more akin to "play" than to other games. The closest game I would compare flOw to would be Feeding Frenzy (Xbox Live Arcade), or similar, where you are trying to keep your organism alive. The microscopic world does serve as a surreal backdrop for this type of game, however, as well as present a world that is alien enough to inspire the strong discovery gameplay element found in flOw.

The PSP version of flOw is not the first version out there, mind you, and the PS3 version has larger levels, but I found the PSP version of flOw to be a perfect fit for a handheld system and, more specifically, the really simplistic control scheme kept the PSP's controls from being problematic. You move around with the analog nub and almost anything else you hit activates your organism's special "boost" effect - for some organisms, this is an attack, for others, it's defensive or simply a speed boost.

Multiplayer play in flOw supports up to 4 players, via an ad-hoc wireless connection. There is no menu item to select multiplayer, however; if there is another player within range, the PSPs automatically sync and you join a game together. In other words, if you don't want to play a multiplayer game, you'll need to turn your wireless off while playing flOw. I played a two player game with J.R. Nip, and it's a cooperative gameplay experience (you can't hurt each other - directly, anyway) where you each explore a level together. If one organism (or player) does something that would change the "level" that you're on, all players change the level together. This includes the "pause level" reached by hitting the Start button. The multiplayer game can be a nice way to introduce a friend to flOw; I basically gave J.R. Nip a guided tour. Also, while it's built to be cooperative, the ability for one player to cause both players to change levels together has the potential to introduce a competitive aspect to the game.

The only complaint I would have about flOw would be that it is too short. Each organism has its own set of levels, but there are only six different organisms, including the last one, whose levels display credits and have nothing that can hurt you. The game is relaxing and almost therapeutic, however, and the goals aren't too overly defined, so you can play just to relax or to see how quickly you can get through the whole game... the replay value is, essentially, limited to your imagination and your interest. I can see myself picking this game up in the future, if I need to kick back for a bit.

While the controls and the graphics were simplistic, the game of flOw is, to a great extent, a game of discovery. As you play, you'll determine what is good to eat, what is poisonous, how to navigate around the watery world and how to use what you can see to your best advantage. On that point, one thing that just screamed "microscope" to me is this strange, layered world in which you play. The "world" consists of a series of parallel layers, and you can just make out next layer in the background of the current one. If you've ever used a microscope, you're probably familiar with this effect, as different layers can be seen, while only one can be in focus at a given time.

This multi-layer view is not only a cool visual effect that really helps to reinforce the feeling of a microscopic playing field, but it also serves as an excellent tool for planning how - and when - you want to approach the next level. Usually you can determine, at least to some degree, what the next level has in store for you. You can tell if there are large creatures moving around or if there are merely a lot of small creatures. You can tell if there is another creature similar to you and whether it's larger or smaller than yours. You can see if there are new types of organisms you haven't encountered before, even though you're not sure what they are. This "recon" information can prove very helpful, if used carefully. Watch how the organisms move. Are they fast or slow? Do they move in a snake-like fashion, float about or stay mostly still? Sizing up organisms before you enter the same plane can make the game easier to play.

The other thing that can adjust the difficulty is, quite frankly, the game itself. flOw has a self-adjusting difficulty feature. When you get to a point that you lose all of your health, you get knocked backwards a level. In this method, you can progress at your own pace. A word of warning, however: you might not want to clear everything as you progress. Otherwise, you will find "health" hard to find on previous levels.

As a little strategy tip, the "Start" button will pause the game, but the way flOw pauses is to move your organism to a threat-free "limbo" level, where you can eat the red organism to return to the level at hand or eat the blue organism to return to the game's main menu. Usually, entering this pause level and returning to the game in progress will cause hostile enemies to "cool off." Additionally, you can return to your game by pressing "Start" again, making it possible to "drop-in" in a more surgical and strategic way. I was able to use this method to drop into levels inside of another organism, getting past its defenses. It's not the only way, but it's a nice trick to have up your sleeve.

If you're interested in User Interface design, flOw is an excellent example of a minimalist approach that works. There is, essentially, no detectable U.I. in flOw; everything you do is presented as in-game actions, whether it be selecting an organism to play as or the Pause menu, there is never anything that takes you out of the game's submersion. Even the multiplayer functionality doesn't require a menu. If you're playing near others and you have your WiFi switch turned on, you'll play multiplayer. If not, you're playing a single player game. This is an amazingly simple way to handle these things, causing one to wonder why this hasn't been done before.

Some people might not "get" a game like flOw. There are no guns, no explosions, no blood-pumping soundtrack. What there is, however, is a goal: to survive, grow and evolve. There are dangers to avoid and objectives to be met. flOw is a game; it's just a lot more laid back than most other games.

The adjustable difficulty level feature works on its own and without any interaction, but some gamers may be confused by the fact that you can't "die," per se. Truthfully, the only difference here is that you never meet with "total failure" and have to start over at the beginning or are told that you have lost. You may have to back up a little bit, but flOw's system for adjusting difficulty automatically avoids many of the normal trappings of videogames that send you hurtling back to the beginning of a level or, worse yet, the entire game, or causes you to want to save your progress every few seconds.

Instead, flOw presents a videogame that can actually be relaxing, as it is devoid of many of the things that make videogames stressful and it allows for safe areas in the areas you've cleared, even if you leave smaller "component" organisms behind... Small organisms that serve as food can't hurt you, they just float around until its lunchtime.

A videogame that can be described as "relaxing" is a rare thing indeed. A PSP game whose controls aren't the least bit clunky is just as rare. flOw provides both of these in a beautiful package while challenging everything we know about user interfaces in games. I highly recommend flOw; it's one of those rare games we like to call, "unique."