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+
+The aim of Chocolate Doom is to behave as closely to Vanilla Doom as
+possible.  As a result, you may experience problems that you would
+also experience when using Vanilla Doom.  These are not "bugs" as
+Chocolate Doom is behaving as intended.
+
+This is not intended to be a comprehensive list of Vanilla Doom bugs.
+For more information, consult the "engine bugs" page of the Doom Wiki.
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+== Game exits after title screen with message about game version ==
+
+The game may exit after the title screen is shown, with a message like
+the following:
+
+    Demo is from a different game version!
+    (read 106, should be 109)
+
+    *** You may need to upgrade your version of Doom to v1.9. ***
+        See: http://doomworld.com/files/patches.shtml
+        This appears to be v1.6/v1.666.
+
+This usually indicates that your IWAD file that you are using to play
+the game (usually named doom.wad or doom2.wad) is out of date.
+Chocolate Doom only supports the v1.9 IWAD file.
+
+To fix the problem, you must upgrade to the v1.9 IWAD file.  The URL
+in the message has downloadable upgrade patches that you can use to
+upgrade.
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+== Game exits in demo loop when playing Final Doom ==
+
+When playing with the Final Doom IWAD files (tnt.wad, plutonia.wad),
+if you leave the game at the title screen to play through the demo
+loop, it will eventually exit with the following error message:
+
+    W_GetNumForName: demo4 not found!
+
+This is the same behavior as the Vanilla executables that were
+bundled with Final Doom.  When Ultimate Doom was developed, a fourth
+demo was added to the demo loop, and this change was retained in the
+Final Doom version of the executable.  However, the Final Doom IWADs
+do not include a fourth demo, so the game crashes.
+
+One way to work around this problem is to make the game emulate the
+original (pre-Ultimate Doom) v1.9 executable.  To do this, add the
+command line argument "-gameversion 1.9" when running the game.
+However, be aware this version does have some subtle differences that
+will affect the playback of Final Doom demos (lost soul bouncing,
+teleport behavior).
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+== Game exits when accessing the options menu ==
+
+The game may exit with the message "Bad V_DrawPatch" when accessing
+the options menu, if you have your mouse sensitivity set high.
+
+The Doom options menu has a slider that allows the mouse sensitivity
+to be controlled; however, it has only a very limited range. It is
+common for experienced players to set a mouse sensitivity that is much
+higher than what can be set via the options menu. The setup program
+allows a larger range of values to be set.
+
+However, setting very high sensitivity values causes the game to exit
+when accessing the options menu under Vanilla Doom. Because Chocolate
+Doom aims to emulate Vanilla Doom as closely as possible, it does the
+same thing.
+
+One solution to the problem is to set a lower mouse sensitivity.
+Alternatively, all of the settings in the options menu can be
+controlled through Doom's key bindings anyway:
+
+    End game: F7
+    Messages on/off: F8
+    Graphic detail high/low: F5
+    Screen size smaller/larger: -/+
+    Sound volume menu: F4
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+== Game exits with "Savegame buffer overrun" when saving the game ==
+
+If you are playing on a particularly large level, it is possible that
+when you save the game, the game will quit with the message "Savegame
+buffer overrun".
+
+Vanilla Doom has a limited size memory buffer that it uses for saving
+games.  If you are playing on a large level, the buffer may be too
+small for the entire savegame to fit.  Chocolate Doom allows the limit
+to be disabled: in the setup tool, go to the "compatibility" menu and
+disable the "Vanilla savegame limit" option.
+
+If this error happens to you, your game has not been lost!  A file
+named temp.dsg is saved; rename this to doomsav0.dsg to make it appear
+in the first slot in the "load game" menu.  (On Unix systems, you will
+need to look in the .chocolate-doom/savegames directory in your home
+directory)
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+== Game ends suddenly when recording a demo ==
+
+If you are recording a very long demo, the game may exit suddenly.
+Vanilla Doom has a limited size memory buffer that it uses to save the
+demo into.  When the buffer is full, the game exits.  You can tell if
+this happens, as the demo file will be around 131,072 bytes in size.
+
+You can work around this by using the -maxdemo command line parameter
+to specify a larger buffer size.  Alternatively, the limit can be
+disabled: in the setup tool, go to the compatibility menu and disable
+the "Vanilla demo limit" option.
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+== Game exits with a message about "visplanes" ==
+
+The game may exit with one of these messages:
+
+    R_FindPlane: no more visplanes
+    R_DrawPlanes: visplane overflow (129)
+
+This is known as the "visplane overflow" limit and is one of the most
+well-known Vanilla Doom engine limits.  You should only ever experience
+this when trying to play an add-on level.  The level you are trying to
+play is too complex; it was most likely designed to work with a limit
+removing source port.
+
+More information can be found here:
+
+    http://rome.ro/lee_killough/editing/visplane.shtml
+