Sorry for the long abscence, I was very busy the last months.
I tested the frontlight, but I noticed, that it's impossible to see what the display is showing...
Does somebody have an idea for a solution? By the way, the result is worse when using a diffused protection film on the Gameboy display, so I used a clear protection film.
The display shows the mainscreen of "The Legend of Zelda: Oracle of Seasons".