[CNN.com] 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.

The content of the game changes according to time:
- the Undead come out at night and stay in dungeons during the day

and according to sunlight:
- Solar Gun power is charged by sunlight.
- Puddles dry up if exposed to sunlight continuously.
- 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.