diff --git a/linuxdoom-1.10/r_bsp.cpp b/linuxdoom-1.10/r_bsp.cpp
index f43e2bb..70883cb 100644
--- a/linuxdoom-1.10/r_bsp.cpp
+++ b/linuxdoom-1.10/r_bsp.cpp
@@ -24,7 +24,6 @@
 #include "m_bbox.h"
 
 #include "r_main.h"
-#include "r_plane.h"
 #include "r_things.h"
 
 // State.
@@ -33,6 +32,7 @@
 import system;
 import sky;
 import setup;
+import plane;
 
 // 
 
diff --git a/linuxdoom-1.10/r_draw.h b/linuxdoom-1.10/r_draw.h
index ab330d2..d0d438c 100644
--- a/linuxdoom-1.10/r_draw.h
+++ b/linuxdoom-1.10/r_draw.h
@@ -21,6 +21,10 @@
 
 #pragma once
 
+#include <cstddef>
+
+#include "m_fixed.h"
+
 // This could be wider for >8 bit display.
 // Indeed, true color support is posibble
 //  precalculating 24bpp lightmap/colormap LUT.
diff --git a/linuxdoom-1.10/r_main.cpp b/linuxdoom-1.10/r_main.cpp
index 7ad56e7..75be4af 100644
--- a/linuxdoom-1.10/r_main.cpp
+++ b/linuxdoom-1.10/r_main.cpp
@@ -33,7 +33,6 @@
 #include "r_main.h"
 #include "r_draw.h"
 #include "r_things.h"
-#include "r_plane.h"
 #include "r_bsp.h"
 
 import system;
@@ -42,6 +41,7 @@ import sky;
 import setup;
 import main;
 import doom;
+import plane;
 
 // Fineangles in the SCREENWIDTH wide window.
 #define FIELDOFVIEW 2048
@@ -647,8 +647,6 @@ void R_Init(void) {
   printf("\nR_InitTables");
 
   R_SetViewSize(screenblocks, detailLevel);
-  R_InitPlanes();
-  printf("\nR_InitPlanes");
   R_InitLightTables();
   printf("\nR_InitLightTables");
   R_InitSkyMap();
diff --git a/linuxdoom-1.10/r_plane.h b/linuxdoom-1.10/r_plane.h
deleted file mode 100644
index 9a8a30e..0000000
--- a/linuxdoom-1.10/r_plane.h
+++ /dev/null
@@ -1,52 +0,0 @@
-// Emacs style mode select   -*- C++ -*-
-//-----------------------------------------------------------------------------
-//
-// $Id:$
-//
-// Copyright (C) 1993-1996 by id Software, Inc.
-//
-// This source is available for distribution and/or modification
-// only under the terms of the DOOM Source Code License as
-// published by id Software. All rights reserved.
-//
-// The source is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// FITNESS FOR A PARTICULAR PURPOSE. See the DOOM Source Code License
-// for more details.
-//
-// DESCRIPTION:
-//	Refresh, visplane stuff (floor, ceilings).
-//
-//-----------------------------------------------------------------------------
-
-#pragma once
-
-#include "r_data.h"
-
-// Visplane related.
-extern short *lastopening;
-
-typedef void (*planefunction_t)(int top, int bottom);
-
-extern planefunction_t floorfunc;
-extern planefunction_t ceilingfunc_t;
-
-extern short floorclip[SCREENWIDTH];
-extern short ceilingclip[SCREENWIDTH];
-
-extern fixed_t yslope[SCREENHEIGHT];
-extern fixed_t distscale[SCREENWIDTH];
-
-void R_InitPlanes(void);
-
-void R_ClearPlanes(void);
-
-void R_MapPlane(int y, int x1, int x2);
-
-void R_MakeSpans(int x, int t1, int b1, int t2, int b2);
-
-void R_DrawPlanes(void);
-
-visplane_t *R_FindPlane(fixed_t height, int picnum, int lightlevel);
-
-visplane_t *R_CheckPlane(visplane_t *pl, int start, int stop);
diff --git a/linuxdoom-1.10/r_segs.cpp b/linuxdoom-1.10/r_segs.cpp
index 98f3560..0d4b250 100644
--- a/linuxdoom-1.10/r_segs.cpp
+++ b/linuxdoom-1.10/r_segs.cpp
@@ -28,10 +28,10 @@
 #include "r_main.h"
 #include "r_things.h"
 #include "r_draw.h"
-#include "r_plane.h"
 
 import system;
 import sky;
+import plane;
 
 // OPTIMIZE: closed two sided lines as single sided
 
diff --git a/src/doom/doom.ixx b/src/doom/doom.ixx
index 86713ad..7a593ca 100644
--- a/src/doom/doom.ixx
+++ b/src/doom/doom.ixx
@@ -7,4 +7,4 @@ export import :ticcmd;
 export import :player;
 export import :event;
 export import :tables;
-export import :strings;
\ No newline at end of file
+export import :strings;
diff --git a/linuxdoom-1.10/r_plane.cpp b/src/doom/plane.ixx
similarity index 91%
rename from linuxdoom-1.10/r_plane.cpp
rename to src/doom/plane.ixx
index 24c5229..86092be 100644
--- a/linuxdoom-1.10/r_plane.cpp
+++ b/src/doom/plane.ixx
@@ -22,20 +22,36 @@
 //	Moreover, the sky areas have to be determined.
 //
 //-----------------------------------------------------------------------------
-
+module;
 #include <stdlib.h>
-
-
-#include "r_plane.h"
 #include "r_draw.h"
 #include "r_main.h"
 #include "r_things.h"
-
+export module plane;
 
 import system;
 import wad;
 import sky;
 
+// Visplane related.
+export inline short *lastopening;
+
+typedef void (*planefunction_t)(int top, int bottom);
+
+extern planefunction_t floorfunc;
+extern planefunction_t ceilingfunc_t;
+
+//
+// Clip values are the solid pixel bounding the range.
+//  floorclip starts out SCREENHEIGHT
+//  ceilingclip starts out -1
+//
+export inline short floorclip[SCREENWIDTH];
+export inline short ceilingclip[SCREENWIDTH];
+
+export inline fixed_t yslope[SCREENHEIGHT];
+export inline fixed_t distscale[SCREENWIDTH];
+
 planefunction_t floorfunc;
 planefunction_t ceilingfunc;
 
@@ -47,21 +63,12 @@ planefunction_t ceilingfunc;
 #define MAXVISPLANES 128
 visplane_t visplanes[MAXVISPLANES];
 visplane_t *lastvisplane;
-visplane_t *floorplane;
-visplane_t *ceilingplane;
+export visplane_t *floorplane;
+export visplane_t *ceilingplane;
 
 // ?
 #define MAXOPENINGS SCREENWIDTH * 64
 short openings[MAXOPENINGS];
-short *lastopening;
-
-//
-// Clip values are the solid pixel bounding the range.
-//  floorclip starts out SCREENHEIGHT
-//  ceilingclip starts out -1
-//
-short floorclip[SCREENWIDTH];
-short ceilingclip[SCREENWIDTH];
 
 //
 // spanstart holds the start of a plane span
@@ -76,8 +83,6 @@ int spanstop[SCREENHEIGHT];
 lighttable_t **planezlight;
 fixed_t planeheight;
 
-fixed_t yslope[SCREENHEIGHT];
-fixed_t distscale[SCREENWIDTH];
 fixed_t basexscale;
 fixed_t baseyscale;
 
@@ -86,14 +91,6 @@ fixed_t cacheddistance[SCREENHEIGHT];
 fixed_t cachedxstep[SCREENHEIGHT];
 fixed_t cachedystep[SCREENHEIGHT];
 
-//
-// R_InitPlanes
-// Only at game startup.
-//
-void R_InitPlanes(void) {
-  // Doh!
-}
-
 //
 // R_MapPlane
 //
@@ -158,7 +155,7 @@ void R_MapPlane(int y, int x1, int x2) {
 // R_ClearPlanes
 // At begining of frame.
 //
-void R_ClearPlanes(void) {
+export void R_ClearPlanes(void) {
   int i;
   angle_t angle;
 
@@ -185,7 +182,7 @@ void R_ClearPlanes(void) {
 //
 // R_FindPlane
 //
-visplane_t *R_FindPlane(fixed_t height, int picnum, int lightlevel) {
+export visplane_t *R_FindPlane(fixed_t height, int picnum, int lightlevel) {
   visplane_t *check;
 
   if (picnum == skyflatnum) {
@@ -222,7 +219,7 @@ visplane_t *R_FindPlane(fixed_t height, int picnum, int lightlevel) {
 //
 // R_CheckPlane
 //
-visplane_t *R_CheckPlane(visplane_t *pl, int start, int stop) {
+export visplane_t *R_CheckPlane(visplane_t *pl, int start, int stop) {
   int intrl;
   int intrh;
   int unionl;
@@ -298,7 +295,7 @@ void R_MakeSpans(int x, int t1, int b1, int t2, int b2) {
 // R_DrawPlanes
 // At the end of each frame.
 //
-void R_DrawPlanes(void) {
+export void R_DrawPlanes(void) {
   visplane_t *pl;
   int light;
   int x;