Our first impression on booting up Osmos was, "Awww...purty colors." Our second impression, after a few minutes of playing, was that Osmos bears a certain resemblance to what Wii gamers experienced with Orbient, part of Nintendo's Artstyle series of WiiWare downloads. As you dig deeper into Osmos, it becomes clear that the Orbient resemblance largely ends after recognizing that both games feature floating orbs and ambient music. All the same, fans of Orbient that longed for more of this type of action should welcome Osmos with open arms. Not that they are remotely in competition, but of the two, you'll get more mileage out of Osmos.

The graphics in Osmos depict ethereal realms that remind one of looking down into a hi-def petri dish. It's not immediately clear that you're seeing organisms, but some of the objects swirling around while you play seem to have a definite purpose, in an action/reaction type of way. The music accompanying the visuals is a perfect match for the action, although some tracks felt a bit loopy for our tastes. Developer Hemisphere Games prefers the term "ambient" to describe the approach taken with Osmos, which we can buy. There certainly is room for discarding the "Casual" tag, that seems to be becoming more vague and broad with each passing day. Osmos can be played full-screen (glorious) or windowed, if you need to keep your eye on a few things at once. Playing with headphones or good audio is a must, since this game is very much about setting a mood and providing an experience that draws equally on inspiring sights and sounds.

Where Orbient was basically an entire game about gravity, Osmos takes a more varied approach. Sure, there's a piece of Osmos that has a gravity theme, but even in that area you have full control over your "craft," if you can call it that. Each level in Osmos has a measure for success that is almost always connected to merging your blobbish mass with other blobbish masses. At times this is the only goal, stated simply as, "Become the biggest." Other times, you'll grow in service of a secondary goal, like absorbing other sentient masses in the level. As with another "ambient" classic, flOw,, your surroundings in Osmos are fluid and dynamic. Most objects are just in motion, a la Asteroids, but some have a purpose. Some really great A.I. is at work here, such that smaller orbs (those that can move independently) seem aware of when to run away and when to go on the attack. "Survival of the largest" would be the Osmos translation of Darwin, and you'll find most levels are a mad scramble to accumulate smaller particles before they become absorbed.

Osmos doesn't conform to what most games present as "modes." A more subtle approach is used in almost everything about this game, which we loved. There are branching paths you will open up through success in earlier levels, and each path features levels with certain rules at play. Purely ambient play is all about gathering a majority percentage of the total mass in that level, without much external pressure. Other paths introduce different gameplay mechanics involving some aggressors that make your life more difficult, and some challenges for you. At least one style of play has you revolving around a large orb that is constantly pulling you closer as you become larger. Each level plays quickly and features several keyboard shortcuts that let you dial the speed up or down as you like. There's enough challenge to keep most players happy for a long while, and there's no doubt that while Osmos isn't strictly speaking a Casual title, it has those great pick-up/put-down qualities that make so-called Casual titles so easy to return to time and time again.

We mentioned that speed control, and it's interesting how this plays directly into adjusting difficulty in Osmos. Speeding up (using the mouse or keyboard) is a great way to accelerate a level that is clearly already won, or to just provide additional challenge. The slow-down feature is essential for clearing certain levels where even a slight mistake means a re-do. We found that some levels automatically felt frantic, until the speed was dropped back a ways. We loved how the music modulated along with the speed controls, but some might find it annoying. The A.I., as mentioned, is rock solid throughout Osmos. You'll find yourself thinking about how fun this would be as a 4-player co-op or competitive type of game, so maybe that will happen in the future. For now, the CPU is all you'll have to compete against, and there are some very challenging levels. Hemisphere uses those branching paths to provide something for (almost) everyone, ranging from super-relaxed casual players that only like exploring the ambient levels, to twitchy core gamers that want to beat every level in less time with a higher percentage clear. The last group is probably on the outer fringe of the market Osmos is targeting, but for those that want a steep challenge, there's always that speed-up setting!

Simple controls are the name of the game here, but Mac users without a two-button mouse may find it a bit less enjoyable to play between mouse and keyboard. We tried it both ways, and felt that the keyboard controls are preferable to scrolling with the mouse, since there's more precise control. Mac people are used to being left out in the cold by virtue of their non-standard mouse arrangement, and we have mad skillz when it comes to the mouse/keyboard coordination. Osmos does no great disservice by following the 2/3-button convention that 99% of other PC games out there use. Macs with the newest multi-touch mouse will find that they have at least the two-button functionality working in Osmos, right out of the box. Even with one of these, we eventually fell back on the keyboard because it just seemed more effective. Generating the motion and direction required for "piloting" your orb is all done with clicks. You position a targeting cursor against the side of your orb opposite the intended destination, and give a click. More clicks mean more inertia, but since your orb moves by expelling some mass, clicking faster means more loss in size. This very important dynamic in your game makes each click count, and often means that aggressive clickers will buy themselves a one-way ticket to Replay Town.

Replaying isn't a bad thing when you encounter something as unique and well designed as Osmos. Mac gamers should snap this one up immediately and consider themselves lucky. The extremely bargain priced Osmos is a great example of the kind of innovation and execution that makes videogames great. Calling it "art" isn't fair to Osmos, since the connotation then becomes something to ogle instead of something to roll up one's sleeves and dive into. Dive in we did, and happy to report that the water's just fine, motes and all...