diff --git a/BUILD-SYSTEM.adoc b/BUILD-SYSTEM.adoc
index 9ed85ec1..b634eee0 100644
--- a/BUILD-SYSTEM.adoc
+++ b/BUILD-SYSTEM.adoc
@@ -51,8 +51,8 @@ following diagram illustrates the process:
 The following are the resulting WAD files generated by the build
 system:
 
- * +freedoom1.wad+: Phase 1, the _Ultimate Doom_ IWAD file.
- * +freedoom2.wad+: Phase 2, the _Doom II_ IWAD file.
+ * +freedoom1.wad+: Phase 1, the _Ultimate Doom_-compatible IWAD file.
+ * +freedoom2.wad+: Phase 2, the _Doom II_-compatible IWAD file.
  * +freedm.wad+: FreeDM IWAD file, containing deathmatch levels
 
 == Source configuration files
@@ -71,9 +71,8 @@ The +buildcfg.txt+ file is processed using a Python script named
 tool (C Preprocessor).  Variables are defined on the command line,
 based on the type of output target desired:
 
- * +DOOM2+: Build for a Doom II WAD.
- * +DOOM1+: Build for a Doom I WAD.
- * +ULTDOOM+: Include episode four levels.
+ * +PHASE1+: Build for the Phase 1 IWAD.
+ * +PHASE2+: Build for the Phase 2 IWAD.
 
 === Texture configuration file (+lumps/textures/textures.cfg+)
 
@@ -83,20 +82,19 @@ patch names) and +texture2.lmp+ (Doom I only). They are generated
 by the +build-textures+ script; deutex’s internal texture builder
 is deliberately not used for compatibility reasons.
 
-Similarly to the build configuration file, different textures are
-included depending on the output WAD type. The file is passed through
-the +simplecpp+ script to include the appropriate textures. Command
-line variables are defined based on the desired build settings:
+Unlike id’s Doom games, Freedoom includes nearly every texture
+possible in all three of its IWADs.  There are a handful of textures
+that must differ between Phase 1 and 2 for compatibility with Doom 1
+and 2 mods, since their definitions changed in the Doom games.  We
+also include logo textures for FreeDM levels.  The file is passed
+through the +simplecpp+ script to account for the variant textures.
+Command line variables are defined based on the desired build
+settings:
 
- * +DOOM1+: Include textures that only exist in Doom I.
- * +DOOM2+: Include textures that only exist in Doom II.
- * +ULTDOOM+: Include textures that only exist in Ultimate Doom.
+ * +DOOM1_VERSIONS+: Include textures in Phase 1 that would conflict
+   with Phase 2.
  * +FREEDM+: Include textures that are needed for FreeDM.
 
-Note that +DOOM1+ and +DOOM2+ are not mutually exclusive, and the
-default for a Doom II build is to include all of the textures for
-both.
-
 == Generated files
 
 The following files are generated automatically by automated scripts
@@ -118,8 +116,8 @@ configurations for each IWAD file.
 [frame="topbot",grid="none",options="header"]
 |===============================================================
 | Subdirectory             | WAD File        | CPP Variables
-| +lumps/textures/phase1/+ | +freedoom1.wad+ | DOOM1, ULTDOOM
-| +lumps/textures/phase2/+ | +freedoom2.wad+ | DOOM1, DOOM2
+| +lumps/textures/phase1/+ | +freedoom1.wad+ | PHASE1
+| +lumps/textures/phase2/+ | +freedoom2.wad+ | PHASE2
 | +lumps/textures/freedm/+ | +freedm.wad+    | FREEDM
 |===============================================================
 
@@ -135,9 +133,8 @@ WAD files that are built:
 [frame="topbot",grid="none",options="header"]
 |===============================================================
 | Filename             | WAD File           | CPP Variables
-| +wadinfo.txt+        | Resource WAD files | DOOM2
-| +wadinfo_phase1.txt+ | +freedoom1.wad+    | DOOM1, ULTDOOM
-| +wadinfo_phase2.txt+ | +freedoom2.wad+    | DOOM2
+| +wadinfo_phase1.txt+ | +freedoom1.wad+    | PHASE1
+| +wadinfo_phase2.txt+ | +freedoom2.wad+    | PHASE2
 | +wadinfo_freedm.txt+ | +freedm.wad+       | FREEDM
 |===============================================================
 
@@ -180,19 +177,17 @@ It reads level names from the dehacked lumps.
 
 === +playpal.py+
 
-Found in +lumps/cph/misc-lumps+, this script builds the +PLAYPAL+
-lump which contains the 256-color palettes used for special
-effects (injured “red” flash, the green “radiation suit” effect,
-etc.)
+Found in +lumps/playpal+, this script builds the +PLAYPAL+ lump which
+contains the 256-color palettes used for special effects (injured
+“red” flash, the green “radiation suit” effect, etc.)
 
 === +colormap.py+
 
-Found in +lumps/cph/misc-lumps+, this script builds the +COLORMAP+
-lump that is used for the diminished lighting within the game.
-This script is also reused to generate additional colormaps that
-can be used for special effects. It has a number of command line
-options that allow it to do various different colorizing and
-“fog” effects.
+Found in +lumps/colormap+, this script builds the +COLORMAP+ lump that
+is used for the diminished lighting within the game.  This script is
+also reused to generate additional colormaps that can be used for
+special effects. It has a number of command line options that allow it
+to do various different colorizing and “fog” effects.
 
 === +mkgenmidi+