Boktai is a video game series created by Hideo Kojima and published by Konami. The series consists entirely of portable games for the Game Boy Advance and Nintendo DS, and is notable for its unique inclusion of a built-in solar sensor required for gameplay. The final game in the series made use of the solar sensor optional, and did not include one by default. The series revolves around vampire hunters who must use sunlight-based weaponry to combat evil undead creatures. Critics praised the games' unconventional design, although the requirement to play the game outdoors, in order to bring the most color out of the screen of the Game Boy Advance, ensured that it had only a niche audience, with the third game in the series not receiving a release outside of Japan.