Not much is needed for this. The only noteworthy point is that it doesn't work by changing the LHSL to "[the player's surroundings in upper case]": it cannot do this because "the player's surroundings" is not a value. Instead, "[the player's surroundings]" is a text substitution sometimes printing the name of a room, sometimes printing "Darkness", and so on. We must therefore load it into a text first, and then apply "…in upper case".
Test me with "e / s / e".
It is pitch dark, and you can't see a thing.