There's already dark mod?
But good job! I love it!
I'm sorry to be honest I worked on it during the afternoon and then posted it when I decided it was good enough, I simply forgot to check.
Line of sight.
Ie, anything blocked by solids from your player is blacked out.
Maybe even incuding whats behind your charater....
That would be tricky, I'd also have to develop a better understanding of game maker code (I was working with that it was similar to java) but what I would be more afraid of is how constantly processing that in game would affect the frame rate or even lag.