I tried this mechanic before. The main problem is that the light should bounce the walls, otherwise you are close to a wall and cannot orientate yourself. It should also follow the mouse, because moving to flash again disorientate you.
I think the "corners" to pass or move to another area are way to tight, making it hard to keep moving.
Interacting to pick up the key is a bit awkward, I was expecting taking it while I pass on the top of it. Probably you wanted to the player to be aware that the key was there? maybe a "shiny" effect when you flash it would help too
You could use the idea to look for ghosts :)