Boktai is a series of action RPG games for Game Boy Advance and Nintendo DS consoles. The game cartridges use a solar sensor to incorporate sunlight into the game. Depending on the amount of sunlight, places and events in the game are affected.
Boktai series (2003-2006), developed by Konami and produced by Hideo Kojima, consists of four games. The name Boktai comes from Japanese ‘Bokura no Taiyo’, meaning ‘Our Sun’. An attachment onto the game’s cartridge, a solar sensor, measures the amount of sunlight the game is played in. The sunlight is measured in blocks, with a maximum of eight blocks. Sunlight is a key factor to the gameplay of Boktai and necessary in order to progress. Via sunlight, the places, events, equipment etc. are significantly affected by different lighting conditions. In the first game, for example, the player character uses a solar gun that stores sunlight as its energy. This energy can be stored in solar stations which the player can withdraw and use when sunlight is not available. In order to charge the in-game weapon, the player must actually take their console outside in the daytime. Players also have the ability to store solar energy in solar bank to gain interest and pay debt.
All but the third Boktai game have been released in the West. The fourth game was renamed Lunar Knights in the translation, and the familiar character names were changed. The game does not require a light sensor, either.