Commander Keen Episode 4: Secret of the Oracle

Commander Keen Episode 4: Secret of the Oracle
Also known as: Commander Keen: Secret of the Oracle Developer: id Software Publisher: Apogee Software Platform: DOS Released internationally: December 15, 1991 This game has unused graphics. This game has debugging material.

Commander Keen Episode 4: Secret of the Oracle is the first Commander Keen game with a soundtrack and is the first part of the Goodbye, Galaxy! duology, alongside being the debut of the world-famous Dopefish.

Debug Mode

During gameplay, pressing A, 2, and ↵ Return all at once will activate debug mode. (Early versions of the game do not require this step.) Once activated, these keys will perform the following functions:

• F10 + B - Change border color.
• F10 + C - Show number of active/inactive objects in the level.
• F10 + D - Record a demo. Allows for warping to more levels than the level warp cheat.
• F10 + E - Instantly clears the current level.
• F10 + G - Toggles God Mode.
• F10 + I - "Free items!" Gives you 3000 more points, 99 ammo, all four keys and the wetsuit.
• F10 + J - Toggles the "Jump Cheat", similar to the pogo flight God Mode enables in the Invasion of the Vorticons games.
• F10 + M - Display how much memory is in use. Causes graphical corruption when exiting the dialog.
• F10 + N - Turn clipping on and off.
• F10 + P - Pauses the game until the next keypress.
• F10 + S - Turns on and off slow motion.
• F10 + T - View the currently loaded sprites in memory.
  
• F10 + V - "Add Extra VBLs" Makes the game wait for the specified number of CRT refreshes at each cycle of the main game loop.
• F10 + W - Warp to the given level number.
• F10 + Y - Replaces solid tiles with garbage graphics, revealing hidden passageways. This effect persists until quitting to DOS.
  
• F10 + Z - Sets lives to 0 and kills the player (provided God Mode is off).

This also applies to Commander Keen Episodes 5 and 6.

Unused Graphic

It seems that a desert town was planned for Episode 4, but it was removed for unknown reasons. An overworld graphic still exists for this.

(Source: Shikadi - Keen Wiki)

Keen Dreams Leftovers

The level-loading routine from Keen Dreams alongside its version of the "Now Loading" dialog still exists inside the code of Secret of the Oracle, however during game initialization the pointer to said routine gets overwritten. A patch can be used to replace the pointer overwrite with NOPs and see the old loading bar in-game:

# Patch file for Keen - use with CK4PATCH.EXE
%ext ck4
%version 1.4
# Use alternative cache-box from ID_CA.C
%patch $38FF $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90
             $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90 $90
%end

(Source: NY00123, VileR)