diff --git a/common/include/editor/editor.h b/common/include/editor/editor.h
index dbc2df6ac..407b8971f 100644
--- a/common/include/editor/editor.h
+++ b/common/include/editor/editor.h
@@ -31,7 +31,6 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "ui.h"
 #include "fmtcheck.h"
 
-#ifdef __cplusplus
 #include "fwd-window.h"
 #include "fwd-segment.h"
 #include "objnum.h"
@@ -558,5 +557,3 @@ extern void close_all_windows(void);
 //	Amount to stretch a texture map by.
 //	The two different ones are for the two dimensions of a texture map.
 extern fix Stretch_scale_x, Stretch_scale_y;
-
-#endif
diff --git a/common/include/editor/texpage.h b/common/include/editor/texpage.h
index 01d0cdb2a..5c4371504 100644
--- a/common/include/editor/texpage.h
+++ b/common/include/editor/texpage.h
@@ -28,8 +28,8 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 
 #include "ui.h"
 
-#ifdef __cplusplus
 #include "fwd-event.h"
+#include "fwd-segment.h"
 
 extern int TextureLights;
 extern int TextureEffects;
@@ -45,5 +45,3 @@ void texpage_close();
 int texpage_do(const d_event &event);
 
 #endif
-
-#endif
diff --git a/common/main/automap.h b/common/main/automap.h
index bc300d44c..bfd26c7d9 100644
--- a/common/main/automap.h
+++ b/common/main/automap.h
@@ -27,7 +27,6 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 
 #include "pstypes.h"
 
-#ifdef __cplusplus
 #include <cstddef>
 #include "fwd-segment.h"
 #include "dxxsconf.h"
@@ -42,7 +41,6 @@ namespace dsx {
 void do_automap();
 void automap_clear_visited(d_level_unique_automap_state &LevelUniqueAutomapState);
 }
-#endif
 
 #if defined(DXX_BUILD_DESCENT_II)
 #include "object.h"
@@ -50,6 +48,7 @@ void automap_clear_visited(d_level_unique_automap_state &LevelUniqueAutomapState
 #include "d_array.h"
 #include "d_range.h"
 #include "fwd-event.h"
+#include "fwd-game.h"
 #include "segment.h"
 
 namespace dsx {
@@ -91,5 +90,4 @@ extern marker_message_text_t Marker_input;
 extern d_marker_state MarkerState;
 }
 #endif
-
 #endif
diff --git a/common/main/d_levelstate.h b/common/main/d_levelstate.h
index 8831bcb26..03d20815d 100644
--- a/common/main/d_levelstate.h
+++ b/common/main/d_levelstate.h
@@ -10,6 +10,7 @@
 #include "object.h"
 #include "morph.h"
 
+#ifdef dsx
 namespace dcx {
 
 struct d_level_unique_morph_object_state
@@ -58,3 +59,4 @@ struct d_level_unique_object_state
 extern d_level_unique_object_state LevelUniqueObjectState;
 
 }
+#endif
diff --git a/common/main/fwd-wall.h b/common/main/fwd-wall.h
index 8bf073248..45bc63a3c 100644
--- a/common/main/fwd-wall.h
+++ b/common/main/fwd-wall.h
@@ -11,7 +11,6 @@
 #include <type_traits>
 #include <physfs.h>
 #include "piggy.h"
-#include "maths.h"
 #include "textures.h"
 #include "fwd-object.h"
 #include "fwd-segment.h"
diff --git a/common/main/fwd-weapon.h b/common/main/fwd-weapon.h
index 2ac6b5cd7..8174c6c08 100644
--- a/common/main/fwd-weapon.h
+++ b/common/main/fwd-weapon.h
@@ -25,7 +25,6 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 
 #pragma once
 
-#ifdef __cplusplus
 #include "pack.h"
 #include "pstypes.h"
 #include "maths.h"
@@ -36,13 +35,12 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 
 #include "fwd-powerup.h"
 
+#ifdef dsx
 #if defined(DXX_BUILD_DESCENT_II)
 #define LASER_HELIX_MASK        7   // must match number of bits in flags
 #define MAX_SUPER_LASER_LEVEL   laser_level::_6   // Note, laser levels are numbered from 0.
 #endif
 
-#if defined(DXX_BUILD_DESCENT_I) || defined(DXX_BUILD_DESCENT_II)
-
 struct PHYSFS_File;
 #if 0
 void weapon_info_write(PHYSFS_File *, const weapon_info &);
@@ -219,9 +217,7 @@ extern void smega_rock_stuff(void);
 extern void init_smega_detonates(void);
 #endif
 }
-#endif
 
-#ifdef dsx
 namespace dsx {
 void InitWeaponOrdering();
 void CyclePrimary(player_info &);
@@ -238,5 +234,3 @@ void DropCurrentWeapon(player_info &);
 void DropSecondaryWeapon(player_info &);
 }
 #endif
-
-#endif
diff --git a/common/main/gauges.h b/common/main/gauges.h
index 72c7d6ed9..4cc2b504b 100644
--- a/common/main/gauges.h
+++ b/common/main/gauges.h
@@ -31,6 +31,7 @@ struct bitmap_index;
 
 #include "fwd-object.h"
 #include "kconfig.h"
+#include "game.h"
 
 //from gauges.c
 
diff --git a/common/main/kmatrix.h b/common/main/kmatrix.h
index 472b1c70e..fb6cf7786 100644
--- a/common/main/kmatrix.h
+++ b/common/main/kmatrix.h
@@ -47,7 +47,10 @@ enum class kmatrix_network : uint8_t
 }
 
 #ifdef dsx
+#include "kconfig.h"
+
 namespace dsx {
+
 kmatrix_result kmatrix_view(kmatrix_network network, control_info &Controls); // shows matrix screen. Retruns 0 if aborted (quitting game) and 1 if proceeding to next level if applicable.
 kmatrix_result multi_endlevel_score();
 }
diff --git a/common/main/newdemo.h b/common/main/newdemo.h
index 3e539c598..76a24a0cf 100644
--- a/common/main/newdemo.h
+++ b/common/main/newdemo.h
@@ -128,9 +128,9 @@ void newdemo_record_multi_score(unsigned pnum, int score);
 extern void newdemo_record_primary_ammo(int new_ammo);
 extern void newdemo_record_secondary_ammo(int new_ammo);
 void newdemo_record_door_opening(segnum_t segnum, int side);
-void newdemo_record_laser_level(laser_level old_level, laser_level new_level);
 
 #ifdef dsx
+void newdemo_record_laser_level(laser_level old_level, laser_level new_level);
 namespace dsx {
 #if defined(DXX_BUILD_DESCENT_II)
 void newdemo_record_player_afterburner(fix afterburner);
diff --git a/common/main/piggy.h b/common/main/piggy.h
index f3669e7ba..4f9440a99 100644
--- a/common/main/piggy.h
+++ b/common/main/piggy.h
@@ -32,7 +32,6 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "fwd-partial_range.h"
 #include "dxxsconf.h"
 #include "dsx-ns.h"
-#include <array>
 
 #ifdef dsx
 namespace dsx {
@@ -114,7 +113,6 @@ constexpr std::integral_constant<unsigned, 2620> MAX_BITMAP_FILES{};
 #define MAX_SOUND_FILES     MAX_SOUNDS
 
 
-#ifdef dsx
 namespace dsx {
 extern void piggy_bitmap_page_in( bitmap_index bmp );
 void piggy_bitmap_page_out_all();
@@ -129,10 +127,7 @@ static inline void _piggy_page_in(bitmap_index bmp) {
         piggy_bitmap_page_in( bmp );
     }
 }
-}
-#endif
 
-namespace dsx {
 #if defined(DXX_BUILD_DESCENT_I)
 void piggy_read_sounds(int pc_shareware);
 #elif defined(DXX_BUILD_DESCENT_II)
diff --git a/common/main/sounds.h b/common/main/sounds.h
index e35cbee6a..b4e615439 100644
--- a/common/main/sounds.h
+++ b/common/main/sounds.h
@@ -28,6 +28,9 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #define _SOUNDS_H
 
 #include <array>
+#include <cstdint>
+#include <type_traits>
+#include "dsx-ns.h"
 
 #ifdef dsx
 #if defined(DXX_BUILD_DESCENT_I)