The eight icons may be played as though they were part of an instrument. In this way, Songs are learned, which work like spells; each Song creates a different effect. The earliest Song you'll learn is Shield, which protects Naija from projectiles for 30 seconds. Along the way, you'll learn more and more potent Songs to help you survive your journey. Fortunately, the playing of a Song isn't rhythm-based; merely hitting the proper sequence suffices to enact the effect. You can always refresh your memory of how to play each Song by going into inventory and hovering over the Song icon; clicking on the icon will bring up Naija's narration of the in-world effect.

Aquaria follows the save point mechanism of games; you'll run across giant red crystals from time to time, and there you'll be able to save your progress. Additionally, the mapping functionality is extremely useful. Not only is the entire current section of the underwater network displayed, but each unvisited portion is shown as darker than visited portions, and important areas are marked with large icons. In fact, the game goes you one further by providing smaller markers that you can place over areas you want to remember, and even annotate with a short descriptor -- very handy when you need to remember where that previously-inaccessible passageway was.

Finally, Aquaria is full of enemies. These all take the form of undersea creatures from the mundane -- large jellyfish that emit harmful pulses of light; nudibranchs that are harmful when brushed against -- to the exotic -- tiny leaping homunculi that attempt to bash into Naija; projectile-spewing brain-things whose shots very nearly seem to operate like homing missiles. At first, Naija is defenseless against them all, forcing you to focus on evasion, but later she'll learn new Songs that help her fight back. Like any good adventure game, there are minibosses, and they'll take mastery of Naija's movement and skillful application of the proper Song to defeat.

There are a couple of minor quibbles about Aquaria. It can be a little difficult to tell friend from foe; each creature is graphically equal to the other. There's no red outline denoting an enemy, so sometimes you won't realize you're in danger until actually attacked. An example: the very first critters you'll encounter are a bunch of small jellyfish that follow you around for some reason. They're completely intangible to Naija, so I was under the impression that all jellyfish were safe. This turned out not to be the case.

The other issue is the backtracking, which I refer to as the Metroid Mechanic. Early in the game, you'll frequently run across passages that are blocked by boulders and thus impassable. It's not until you've traveled quite a bit of distance later that you come across the Song required to remove these obstacles and must then travel back to these areas to see if you've missed something important.

These aside, however, Aquaria is a wonderful surprise -- this is the game that won the Independent Games Festival Grand Prize in 2007, and now the world will know why. Give the 30-day trial a spin right here on Big Download.