Boktai: The Sun Is in Your Hand

Hideo Kojima, the man best known for bringing the Metal Gear Solid series to life, has come up with an extremely ambitious idea for the Game Boy Advance: harness the energy of sunlight for a video game. This is Boktai, a vampire-hunting action and adventure game that not only encourages players to get out into the fresh air, but actually requires them to do so. Using a special cartridge with a built-in sun sensor, the amount of sunlight outside the game determines how much sunlight is seen in the actual adventure. And since the player's weapon is powered by sunlight, the more sunlight you get, the stronger and more powerful you are in the game.