It's a nice day outside, and the power's out - but the video game addiction lingers. Solution? Boktai, the action/RPG that is already stirring up excitement thanks to the big name and the big concept behind it. Hideo Kojima, of Metal Gear fame, has cooked up a title for the Game Boy Advance that requires real, outdoor sunlight for successful play.

Many readers would have already read that the sunlight's function in Boktai is to power up the protagonist's Gun del Sol, which he uses to fight darkness-loving enemies. It would be more accurate to say that the cartridge's detection of real life sun rays causes the game's digital sun to come out, which allows the Gun to charge and gives the protagonist, Django, other benefits. The sensor that detects the sunlight is contained in a one centimeter long lip on top of the GBA cart, which hangs out of the system. The sensor can differentiate between real sunlight and artificial light, keeping in tone with Mr. Kojima's goal of taking gamers out of doors. The sensor must be fairly sensitive, because the entire game world changes in proportion to the brightness of the sun. When it is sunny in real life, it is sunny in the game world, with flowers blooming and healthy fruits to be found. When Django holds up the Gun to charge it in these conditions, it charges up very quickly. However, when fog or bad orbital timing diminishes the RL sunlight, it becomes dark in the game world, and zombies begin to spring up. Under these conditions, charging is a slow process, so power must be conserved. If Django is indoors (as he often is thanks to the game's many dungeons), then he will have to find a window or a crack in the ceiling to recharge his Gun. Of course, if it isn't sunny outside, there won't be any sun filtering in through these.

The developers have cut the indoor trolls among us some slack. Django can collect potions that add to the charge of the gun, even in complete darkness. Then there's the other end of the spectrum: too much sun for a prolonged period causes the Gun to overheat, and become useless for three minutes, give or take. The ever-considerate Mr. Kojima also has concerns about his fan base contracting skin cancer, apparently.

Mr. Kojima's fingerprints can also be seen on the less complex elements of the gameplay. The lack of ammunition means that Django will often have to avoid his enemies by "attaching" himself to walls and sneaking around, and occasionally distract foes with wall taps. A particularly useful strategy is to lure them into the sunlight, where they are destroyed instantaneously. Not that there's any one way to do these things, as different enemies have different ways of detecting Django. For example, mummies are blind, but they have excellent hearing, necessitating the sneaking. Others have the opposite set of attributes, so Django needs to get them from behind.

The process in which Django fights the vampire bosses is especially interesting. After dispatching the foe initially, our hero seals him in a coffin and has to drag it to a Piledriver, a special imprint in the ground left by the benevolent sunflower, Otenko. Dragging the coffin is a hazard in itself, because the vampire makes a fuss and tries to escape. Django occasionally has to let go of the coffin; otherwise he'll take damage. Once he reaches the Pildriver, he has to position a set of mirrors to pick up the light and hit the coffin.

Indeed, Boktai often plays more like an action game than an RPG. It does have an RPG-style menu system for managing items, and it does have secondary characteristics such as dungeon maps and plenty of puzzle-solving, but it lacks an experience system. Instead, Django's powers increase by collecting upgrades for the Gun, normally found in treasure chests. These upgrades include batteries that increase the energy storage capacity, and different lenses that allow new attacks, such as a spread shot or a twirl-attack. Each attack consumes a different amount of solar energy.

Boktai's graphics are already earning high praise. The textures are well done, and filled with detail. The vamps live in style in castles built from rocks of multiple shades, and ordained with interesting statues and other decorations. All this, plus the quirky angle, gives Boktai a look that is unprecedented on the GBA.

The music is befitting the game's darkish tone: for all the sunlight, the game is about a vampire hunter, after all. The soundtrack succeeds in being creepy when circumstances call for it, and the beat pumps intensely during boss battles.

The sun sensor is more than a gimmick; it is a device used to put the driving force in solid gameplay elements. Boktai aims to please gamers in as many ways possible - it even has a multiplayer mode where players can load up their Djangos and pit them against each other. Whether it succeeds in all respects remains to be seen, but Boktai has already shown that a little bit of creativity can garner a lot of interest.