Boktai 2: Solar Boy Django is a Game Boy Advance video game that uses a solar screen to power up some of the game's special abilities. It's a sequel to a game titled Boktai: The Sun is in Your Hand and was designed by Metal Gear veteran Hideo Kojima.
The game is very similar to the previous game in the series, though improvements and additions have been included. For example, once you free Violet's grandfather, he'll forge new weapons for you when you bring him two separate weapons. Plus, if there is no sun to be found then you'll be able to store up energy when there is and place it in a solar account. If you've used up all of the spare energy, then you'll be able to take out what are called Dark Loans, which unfortunately cost a hefty price.
In the beginning of the game, you'll be placed in the zombie infested town of San Miguel. A thief will steal all of your weapons, and you'll have to go on without them, eventually finding more to use against the game's various enemies. Early on you'll be granted with the Sol de Vice, which gains power via sun light. You'll have unlimited power via this weapon when in the sunlight, though watch out if you're indoors or if you're playing during a cloudy day.