Pretty hard too. The Elite Five is not included in the gym leader section, but the music that plays when you fight them is the same. Another cool feature that's only for the Gameboy is the internal clock system. Once you do this, the gameboy will do everything according to your time. So if it's nighttime at your place right now, then the Gameboy will also be nighttime.
Same thing goes with daytime.
And that concludes my info section.