Some actions in the game cause glitches in the graphics.
Problem
Some specific actions in the game cause glitches in the graphics.
(1) Using Alt+L to show the map without any items will show all tiles outside of the PC's LOS as lit, even if they're darkened. If you light a torch, then extinguish it and use Alt+L again, it will only show the tile you unequipped the torch on, and others you walked to since then, as dark.
(2) Kicking a door down while blind, then casting Darkness, will show the door you kicked down in gray color.
(3) If you enable 'h'ighlight mode, you will often see white blocks in the message area. (Tested in the Windows port)