A GameBoy Advance title "Boktai" uses sunlight as an essential part of the game. The amount of light determines the amount of power your hero has to defeat his enemies.

There is a solar sensor ! The game contents changes also with the intensity or amount of sunlight that the solar sensor receives.

When there is strong sunlight, solar energy charges up quickly. When weak, it charges up slowly. Sunlight is required mainly to charge energy to the solar gun which is the player's only weapon, and to fight the boss at the Pile Driver. And during moments other than these, the sensor will detect solar energy, causing the game content to change.

There are two gauges at the bottom right of the screen. The one on the top is the "solar gun gauge" that shows how much is left in the battery of the solar gun. The one on the bottom is the "solar gauge" that shows how strong the sunlight detected by the solar sensor at real time is. In order to charge solar energy to the solar gun, press the A Button when the solar gauge is responding.

- The stronger the sunlight, the stronger the wind in certain areas. - There are enemies that reveal themselves when the sunlight is weak. - There are enemies that slow down when the sunlight is weak. - The Pile Driver becomes more powerful.