What is the Theme for the Game Jam?

To be more specific:

This competition is about making software that can run on actual game boy hardware.

• The final deliverable must consist of a GB or GBC ROM file.
• GBC features are allowed
• SGB features are allowed (but don't rely on them)
• You can use RGBDS (ASM), GBDK (C), ZGB (C), GB Studio, or anything that produces a valid ROM.