Ikaruga is a shoot-em-up (shmup) title designed by Treasure and produced by Atari. The game was first released as an arcade, then ported to the Dreamcast, Gamecube, and most recently as a download on XBox Live Arcade.
Ikaruga is a curtain-fire style shmup, which is to say there are many bullets in intricate patterns on-screen; with the added dynamic of polarity. You can align your ship to light or dark, and absorb bullets of the color whose affinity your ship matches. Bullets of the opposing affinities will destroy your ship. The way the game manages to challenge you despite being able to absorb at least half of the bullets on-screen at any given time is impressive, with consideration to clever level design and beautifully scripted bullet patterns.
It's easy to forget which affinity I am on the fly.
Graphically speaking, the game feels dated by modern standards, but it's still visually appealing. The bullet patterns in battle are often less elegant than other Shmup titles, but the level design and other aesthetic elements make up for it during normal level progression.
Unlike most other top-scrolling Shmups, Ikaruga has elaborate level designs, which provide a sort of haven from the usual elements found in games like these. Because of this, it provides unique gameplay that is refreshing to progress through in regard to design elements and atmosphere.
As well as level design, Ikaruga uses the polarity system interestingly. Because the entire game is polarity-centric, there is a lot of strategy involved with how the player progresses through the level. The enemy's polarity also deals a large part in how players may need to approach the game from a strategic standpoint. It's a great mechanic that performs well, and doesn't make the game too easy.
Co-Op provides another interesting layer of gameplay.
The music is very fitting for this game. It's in my most highly rated soundtracks for gaming, and certainly lends something beautiful to the play experience. The sound is sometimes whimsical and sometimes tense, which works well with the light and airy feel of certain levels as well as the harder, grittier combat sections.
Although, this game can be frustratingly difficult. Even after many hours of practice, simple mistakes and extremely challenging situations can make even millimeters the only distance between you and death. Despite this, the difficulty is never quite enough to make it worth quitting, but will be frustrating.
Simply put, Ikaruga is not for everyone. There's almost no way to play Ikaruga casually, so it's all-or-nothing. The difficulty makes this a strange title to recommend because there's so much opinion variance from player to player. The difficulty curve is also rather steep, which challenges the player's patience many times throughout the experience.
Bottom Line: It's a great game that has many fantastic concepts behind it, a strong following, but it isn't the type of game that many casual gamers will enjoy.
Recommendation: Rent it/Download the Demo. That's not to say it isn't worth keeping or playing in full, but it's a game that appeals to a niche-community. If you like shmups, then don't hesitate to buy this game immediately.