The game now has a simple line of sight algorithm. Its simplicity is based on the restriction that the game world is made up of corridors a single tile wide, and does not contain larger open spaces. Line of sight is therefore always along corridors, in four directions. In addition, tiles that are directly adjacent to a visible corridor are also visible, so you can see around the corner a little bit.
Visible tiles are drawn in full brightness, explored but not currently visible tiles are darker, and unexplored tiles are empty. Only entities that are on a visible tile are drawn.