diff --git a/source/bsp.h b/source/bsp.h
index b97d46535..2254976ad 100644
--- a/source/bsp.h
+++ b/source/bsp.h
@@ -18,8 +18,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __AJBSP_BSP_H__
-#define __AJBSP_BSP_H__
+#pragma once
 
 #include <string>
 
@@ -136,7 +135,5 @@ build_result_e BuildLevel(int lev_idx);
 
 } // namespace ajbsp
 
-#endif /* __AJBSP_BSP_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/bsp_local.h b/source/bsp_local.h
index 9fed0abeb..dfbbd6cfc 100644
--- a/source/bsp_local.h
+++ b/source/bsp_local.h
@@ -18,8 +18,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __AJBSP_LOCAL_H__
-#define __AJBSP_LOCAL_H__
+#pragma once
 
 #include <vector>
 
@@ -625,7 +624,5 @@ void RoundOffBspTree();
 
 } // namespace ajbsp
 
-#endif /* __AJBSP_LOCAL_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/bsp_utility.h b/source/bsp_utility.h
index bdef10d81..5e70f9dd4 100644
--- a/source/bsp_utility.h
+++ b/source/bsp_utility.h
@@ -17,8 +17,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __AJBSP_UTILITY_H__
-#define __AJBSP_UTILITY_H__
+#pragma once
 
 namespace ajbsp
 {
@@ -34,7 +33,5 @@ double ComputeAngle(double dx, double dy);
 
 } // namespace ajbsp
 
-#endif /* __AJBSP_UTILITY_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/bsp_wad.h b/source/bsp_wad.h
index 1af443f0f..cdb018406 100644
--- a/source/bsp_wad.h
+++ b/source/bsp_wad.h
@@ -16,8 +16,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __AJBSP_WAD_H__
-#define __AJBSP_WAD_H__
+#pragma once
 
 #include <vector>
 
@@ -327,7 +326,5 @@ class Wad_file
 
 } // namespace ajbsp
 
-#endif /* __AJBSP_WAD_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/csg_doom.cc b/source/csg_doom.cc
index 4487691be..4c2e977bc 100644
--- a/source/csg_doom.cc
+++ b/source/csg_doom.cc
@@ -24,7 +24,6 @@
 
 #include "csg_local.h"
 #include "csg_main.h"
-#include "dm_extra.h"
 #include "g_doom.h"
 #ifndef CONSOLE_ONLY
 #include "hdr_fltk.h"
diff --git a/source/csg_local.h b/source/csg_local.h
index 7999349b8..87dc99096 100644
--- a/source/csg_local.h
+++ b/source/csg_local.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OBLIGE_CSG_LOCAL_H__
-#define __OBLIGE_CSG_LOCAL_H__
+#pragma once
 
 #include <vector>
 
@@ -231,7 +230,5 @@ region_c *CSG_PointInRegion(double x, double y);
 
 void CSG_Shade();
 
-#endif /* __OBLIGE_CSG_LOCAL_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/csg_main.h b/source/csg_main.h
index 80f9858d6..0ebb409e7 100644
--- a/source/csg_main.h
+++ b/source/csg_main.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OBLIGE_CSG_MAIN_H__
-#define __OBLIGE_CSG_MAIN_H__
+#pragma once
 
 #include <stdint.h>
 
@@ -277,7 +276,5 @@ csg_property_set_c *CSG_LookupTexProps(std::string name);
 
 void CSG_LinkBrushToEntity(csg_brush_c *B, std::string link_key);
 
-#endif /* __OBLIGE_CSG_MAIN_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/dm_extra.cc b/source/dm_extra.cc
index 2cd355b37..73bcd21a5 100644
--- a/source/dm_extra.cc
+++ b/source/dm_extra.cc
@@ -19,8 +19,6 @@
 //
 //------------------------------------------------------------------------
 
-#include "dm_extra.h"
-
 #include "csg_main.h"
 #include "g_doom.h"
 #ifndef CONSOLE_ONLY
diff --git a/source/dm_extra.h b/source/dm_extra.h
deleted file mode 100644
index 90403de14..000000000
--- a/source/dm_extra.h
+++ /dev/null
@@ -1,28 +0,0 @@
-//------------------------------------------------------------------------
-//  EXTRA stuff for DOOM
-//------------------------------------------------------------------------
-//
-//  OBSIDIAN Level Maker
-//
-//  Copyright (C) 2021-2022 The OBSIDIAN Team
-//  Copyright (C) 2008-2017 Andrew Apted
-//
-//  This program is free software; you can redistribute it and/or
-//  modify it under the terms of the GNU General Public License
-//  as published by the Free Software Foundation; either version 2
-//  of the License, or (at your option) any later version.
-//
-//  This program is distributed in the hope that it will be useful,
-//  but WITHOUT ANY WARRANTY; without even the implied warranty of
-//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-//  GNU General Public License for more details.
-//
-//------------------------------------------------------------------------
-
-#ifndef __OBLIGE_DM_EXTRA_H__
-#define __OBLIGE_DM_EXTRA_H__
-
-#endif /* __OBLIGE_DM_EXTRA_H__ */
-
-//--- editor settings ---
-// vi:ts=4:sw=4:noexpandtab
diff --git a/source/dm_prefab.cc b/source/dm_prefab.cc
index 89f4fd529..2e6a4d690 100644
--- a/source/dm_prefab.cc
+++ b/source/dm_prefab.cc
@@ -58,8 +58,6 @@
 //
 //------------------------------------------------------------------------
 
-#include "dm_prefab.h"
-
 #include "csg_main.h"
 #include "g_doom.h"
 #include "poly.h"
diff --git a/source/dm_prefab.h b/source/dm_prefab.h
deleted file mode 100644
index cda334955..000000000
--- a/source/dm_prefab.h
+++ /dev/null
@@ -1,28 +0,0 @@
-//------------------------------------------------------------------------
-//  DOOM PREFAB loader
-//------------------------------------------------------------------------
-//
-//  OBSIDIAN Level Maker
-//
-//  Copyright (C) 2021-2022 The OBSIDIAN Team
-//  Copyright (C) 2008-2017 Andrew Apted
-//
-//  This program is free software; you can redistribute it and/or
-//  modify it under the terms of the GNU General Public License
-//  as published by the Free Software Foundation; either version 2
-//  of the License, or (at your option) any later version.
-//
-//  This program is distributed in the hope that it will be useful,
-//  but WITHOUT ANY WARRANTY; without even the implied warranty of
-//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-//  GNU General Public License for more details.
-//
-//------------------------------------------------------------------------
-
-#ifndef __OBLIGE_DM_PREFAB_H__
-#define __OBLIGE_DM_PREFAB_H__
-
-#endif /* __OBLIGE_DM_PREFAB_H__ */
-
-//--- editor settings ---
-// vi:ts=4:sw=4:noexpandtab
diff --git a/source/g_doom.h b/source/g_doom.h
index b6770cee8..0ee8fbb8a 100644
--- a/source/g_doom.h
+++ b/source/g_doom.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef G_DOOM_H_
-#define G_DOOM_H_
+#pragma once
 
 #include "m_lua.h"
 
@@ -290,7 +289,5 @@ struct raw_subsec_t
 
 } // namespace Doom
 
-#endif // G_DOOM_H_
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/hdr_fltk.h b/source/hdr_fltk.h
index 8fc46bc36..dbb132a3e 100644
--- a/source/hdr_fltk.h
+++ b/source/hdr_fltk.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OB_HDR_FLTK__
-#define __OB_HDR_FLTK__
+#pragma once
 
 /* FLTK - Widget Library */
 
@@ -69,6 +68,4 @@
 #include <FL/filename.H>
 #include <FL/fl_ask.H>
 #include <FL/fl_draw.H>
-#include <FL/platform.H>
-
-#endif // __OB_HDR_FLTK__
+#include <FL/platform.H>
\ No newline at end of file
diff --git a/source/hdr_lua.h b/source/hdr_lua.h
index d7a666bca..063b0b76c 100644
--- a/source/hdr_lua.h
+++ b/source/hdr_lua.h
@@ -19,11 +19,8 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OB_HDR_LUA__
-#define __OB_HDR_LUA__
+#pragma once
 
 /* LUA Scripting Language */
 
-#include "../../libraries/minilua/minilua.h"
-
-#endif // __OB_HDR_LUA__
+#include "../../libraries/minilua/minilua.h"
\ No newline at end of file
diff --git a/source/hdr_ui.h b/source/hdr_ui.h
index 88cfa6d16..ea4e6139c 100644
--- a/source/hdr_ui.h
+++ b/source/hdr_ui.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OB_HDR_UI_H__
-#define __OB_HDR_UI_H__
+#pragma once
 
 #include "ui_boxes.h"
 #include "ui_build.h"
@@ -29,6 +28,4 @@
 #include "ui_map.h"
 #include "ui_module.h"
 #include "ui_widgets.h"
-#include "ui_window.h"
-
-#endif /* __OB_HDR_UI_H__ */
+#include "ui_window.h"
\ No newline at end of file
diff --git a/source/headers.h b/source/headers.h
index 5eec117a0..ae0b4c4a5 100644
--- a/source/headers.h
+++ b/source/headers.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OBLIGE_INCLUDES_H__
-#define __OBLIGE_INCLUDES_H__
+#pragma once
 
 // we C++
 #ifdef NULL
@@ -76,7 +75,5 @@
 
 const char *ob_gettext(const char *s);
 
-#endif /* __OBLIGE_INCLUDES_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/images.h b/source/images.h
index 1c2418918..6cccc8b33 100644
--- a/source/images.h
+++ b/source/images.h
@@ -1,7 +1,6 @@
 // Various internal images used by Obsidian
 
-#ifndef __OBSIDIAN_LOGOS_H__
-#define __OBSIDIAN_LOGOS_H__
+#pragma once
 
 #include "headers.h"
 
@@ -5262,6 +5261,4 @@ const uint8_t image_data_RELIEF[64 * 64] = {
     31,  17,  17,  17,  20,  20,  20,  20,  20,  20,  20,  17,  20,  20,  20,  20,  20,  20,  17,  17,  20,  20,  20,
     20,  20};
 
-const logo_image_t logo_RELIEF = {"RELIEF", 64, 64, image_data_RELIEF};
-
-#endif /* __OBSIDIAN_LOGOS_H__ */
+const logo_image_t logo_RELIEF = {"RELIEF", 64, 64, image_data_RELIEF};
\ No newline at end of file
diff --git a/source/lib_argv.h b/source/lib_argv.h
index 8b103127f..8cdfa08cd 100644
--- a/source/lib_argv.h
+++ b/source/lib_argv.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef LIB_ARGV_H_
-#define LIB_ARGV_H_
+#pragma once
 
 #include <string>
 #include <unordered_set>
@@ -40,7 +39,5 @@ bool IsOption(int index);
 
 } // namespace argv
 
-#endif /* __LIB_ARGV_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/lib_parse.h b/source/lib_parse.h
index aab7fae33..f361ec6de1 100644
--- a/source/lib_parse.h
+++ b/source/lib_parse.h
@@ -16,8 +16,7 @@
 //
 //----------------------------------------------------------------------------
 
-#ifndef __AJ_PARSE_H__
-#define __AJ_PARSE_H__
+#pragma once
 
 #include <string>
 
@@ -87,7 +86,5 @@ bool   LEX_Boolean(const std::string &s);
 
 } // namespace ajparse
 
-#endif /* __AJ_PARSE_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/lib_tga.h b/source/lib_tga.h
index 1309c59f4..b72130114 100644
--- a/source/lib_tga.h
+++ b/source/lib_tga.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OBLIGE_TGA_LOADER_H__
-#define __OBLIGE_TGA_LOADER_H__
+#pragma once
 
 // this layout is compatible with Fl_Color (except for alpha)
 typedef unsigned int rgb_color_t;
@@ -58,7 +57,5 @@ class tga_image_c
 
 tga_image_c *TGA_LoadImage(const char *path);
 
-#endif /* __OBLIGE_TGA_LOADER_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/lib_util.h b/source/lib_util.h
index 82e54e604..864fdd270 100644
--- a/source/lib_util.h
+++ b/source/lib_util.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __LIB_UTIL_H__
-#define __LIB_UTIL_H__
+#pragma once
 
 #include <stdint.h>
 
@@ -156,7 +155,5 @@ std::pair<double, double> AlongCoord(double along, double px1, double py1, doubl
 
 bool VectorSameDir(double dx1, double dy1, double dx2, double dy2);
 
-#endif /* __LIB_UTIL_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/lib_wad.h b/source/lib_wad.h
index c085e5cbc..db0d576ba 100644
--- a/source/lib_wad.h
+++ b/source/lib_wad.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef LIB_WAD_H_
-#define LIB_WAD_H_
+#pragma once
 
 /* WAD reading */
 
@@ -69,7 +68,5 @@ struct raw_wad_lump_t
 };
 #pragma pack(pop)
 
-#endif
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/lib_zip.h b/source/lib_zip.h
index 23a0ac15d..c5dbb1f15 100644
--- a/source/lib_zip.h
+++ b/source/lib_zip.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef LIB_ZIP_H_
-#define LIB_ZIP_H_
+#pragma once
 
 #include <stdint.h>
 
@@ -33,7 +32,5 @@ bool ZIPF_AddFile(const std::string &filename, std::string directory);
 bool ZIPF_AddMem(std::string name, uint8_t *data, size_t length);
 bool ZIPF_CloseWrite();
 
-#endif
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/m_addons.h b/source/m_addons.h
index baf6f21a7..68acdcd6e 100644
--- a/source/m_addons.h
+++ b/source/m_addons.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OBLIGE_ADDONS_H__
-#define __OBLIGE_ADDONS_H__
+#pragma once
 
 #include <stdint.h>
 
@@ -57,7 +56,5 @@ extern std::vector<std::string> all_presets;
 
 extern std::map<std::string, int> initial_enabled_addons;
 
-#endif /* __OBLIGE_ADDONS_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/m_cookie.h b/source/m_cookie.h
index 1a81aab9f..5651ed0fa 100644
--- a/source/m_cookie.h
+++ b/source/m_cookie.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OBLIGE_COOKIE_H__
-#define __OBLIGE_COOKIE_H__
+#pragma once
 
 #include <cstdio>
 #include <string>
@@ -58,7 +57,5 @@ void Recent_AddFile(int group, std::string filename);
 void Recent_RemoveFile(int group, std::string filename);
 bool Recent_GetName(int group, int index, std::string name_buf, bool for_menu = false);
 
-#endif /* __OBLIGE_COOKIE_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/m_lua.h b/source/m_lua.h
index a0a63b93d..a59886f9f 100644
--- a/source/m_lua.h
+++ b/source/m_lua.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __SCRIPTING_HEADER__
-#define __SCRIPTING_HEADER__
+#pragma once
 
 #include <stdint.h>
 
@@ -67,7 +66,5 @@ std::string ob_get_password();
 
 bool ob_build_cool_shit();
 
-#endif /* __SCRIPTING_HEADER__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/m_trans.h b/source/m_trans.h
index fb0a5c976..6a9ec5191 100644
--- a/source/m_trans.h
+++ b/source/m_trans.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OBLIGE_I18N_H__
-#define __OBLIGE_I18N_H__
+#pragma once
 
 #include <string>
 
@@ -37,7 +36,5 @@ void Trans_UnInit();
 std::string Trans_GetAvailCode(int idx);
 std::string Trans_GetAvailLanguage(int idx);
 
-#endif /* __OBLIGE_I18N_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/main.h b/source/main.h
index 484c0b1cd..8bbbc5cc7 100644
--- a/source/main.h
+++ b/source/main.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OBSIDIAN_MAIN_H__
-#define __OBSIDIAN_MAIN_H__
+#pragma once
 
 #include <cstddef>
 #include <iostream>
@@ -320,7 +319,5 @@ extern game_interface_c *game_object;
 game_interface_c *Doom_GameObject();
 game_interface_c *Wolf_GameObject();
 
-#endif /* __OBSIDIAN_MAIN_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/poly.h b/source/poly.h
index 51a1aa30a..b2f5f0999 100644
--- a/source/poly.h
+++ b/source/poly.h
@@ -16,8 +16,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __AJPOLY_API_H__
-#define __AJPOLY_API_H__
+#pragma once
 
 // functions provided by the application
 
@@ -326,7 +325,5 @@ polygon_c *Polygon(int index);
 
 } // namespace ajpoly
 
-#endif /* __AJPOLY_API_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/poly_local.h b/source/poly_local.h
index ebdd623f7..d80565a29 100644
--- a/source/poly_local.h
+++ b/source/poly_local.h
@@ -16,8 +16,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __AJPOLY_LOCAL_H__
-#define __AJPOLY_LOCAL_H__
+#pragma once
 
 #include <ctype.h>
 #include <errno.h>
@@ -44,7 +43,5 @@ namespace ajpoly
 
 } // namespace ajpoly
 
-#endif /* __AJPOLY_LOCAL_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/poly_map.h b/source/poly_map.h
index f959db955..b7a18d42c 100644
--- a/source/poly_map.h
+++ b/source/poly_map.h
@@ -16,8 +16,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __AJPOLY_MAP_H__
-#define __AJPOLY_MAP_H__
+#pragma once
 
 #include "poly.h"
 
@@ -70,7 +69,5 @@ ajpoly::vertex_c *NewVertexFromSplit(ajpoly::edge_c *E, double x, double y);
 
 bool VerifyOuterLines();
 
-#endif /* __AJPOLY_MAP_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/poly_util.h b/source/poly_util.h
index ee9a5ddb6..e194c7805 100644
--- a/source/poly_util.h
+++ b/source/poly_util.h
@@ -16,8 +16,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __AJPOLY_UTIL_H__
-#define __AJPOLY_UTIL_H__
+#pragma once
 
 /* ----- FUNCTIONS ---------------------------------- */
 
@@ -27,7 +26,5 @@ void SetErrorMsg(const char *str, ...);
 // compute angle for a 2D vector
 double ComputeAngle(double dx, double dy);
 
-#endif /* __AJPOLY_UTIL_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/poly_wad.h b/source/poly_wad.h
index d11859a14..fd696b9e7 100644
--- a/source/poly_wad.h
+++ b/source/poly_wad.h
@@ -16,8 +16,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __AJPOLY_WAD_H__
-#define __AJPOLY_WAD_H__
+#pragma once
 
 #include <cstdio>
 #include <cstring>
@@ -107,7 +106,5 @@ class wad_c
 
 extern wad_c *the_wad;
 
-#endif /* __AJPOLY_WAD_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/raw_def.h b/source/raw_def.h
index 557928a5e..dd1b2889b 100644
--- a/source/raw_def.h
+++ b/source/raw_def.h
@@ -14,8 +14,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __AJBSP_RAW_DEF_H__
-#define __AJBSP_RAW_DEF_H__
+#pragma once
 
 #include <stdint.h>
 
@@ -496,7 +495,5 @@ typedef enum
 #define ZDOOM_PO_SPAWN_TYPE      9301
 #define ZDOOM_PO_SPAWNCRUSH_TYPE 9302
 
-#endif /* __AJBSP_RAW_DEF_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/slump.h b/source/slump.h
index 4d7a3ac7e..6f1f21392 100644
--- a/source/slump.h
+++ b/source/slump.h
@@ -29,6 +29,8 @@
  * - Please do not call any derivative of this program SLIGE.
  */
 
+#pragma once
+
 #include <stdint.h>
 #include <stdio.h>
 
diff --git a/source/sys_assert.h b/source/sys_assert.h
index cccf7f74a..67670549b 100644
--- a/source/sys_assert.h
+++ b/source/sys_assert.h
@@ -19,8 +19,7 @@
 //
 //----------------------------------------------------------------------------
 
-#ifndef __SYS_ASSERT__
-#define __SYS_ASSERT__
+#pragma once
 
 // -------- the macros --------
 
@@ -55,7 +54,5 @@ __attribute__((noreturn))
 void AssertFail(const char *msg, ...);
 // throw an assertion exception with the given message.
 
-#endif /* __SYS_ASSERT__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/sys_debug.h b/source/sys_debug.h
index 69639af78..507d8f3a5 100644
--- a/source/sys_debug.h
+++ b/source/sys_debug.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __SYS_DEBUG_H__
-#define __SYS_DEBUG_H__
+#pragma once
 
 #include <algorithm>
 #include <fstream>
@@ -87,7 +86,5 @@ using log_display_func_t = void (*)(std::string_view line, void *priv_data);
 
 void LogReadLines(log_display_func_t display_func, void *priv_data);
 
-#endif /* __SYS_DEBUG_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/sys_macro.h b/source/sys_macro.h
index 6ffc96ac3..778788a44 100644
--- a/source/sys_macro.h
+++ b/source/sys_macro.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef SYS_MACRO_H_
-#define SYS_MACRO_H_
+#pragma once
 
 #include <math.h>
 #include <stdint.h>
@@ -47,7 +46,5 @@ inline int RoundToInteger(double x)
     return (int)round(x);
 }
 
-#endif // SYS_MACRO_H_
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/sys_xoshiro.h b/source/sys_xoshiro.h
index 1348c884b..a0408ca14 100644
--- a/source/sys_xoshiro.h
+++ b/source/sys_xoshiro.h
@@ -1,5 +1,7 @@
 // Xoshiro256 Random Generator
 
+#pragma once
+
 #include "../../libraries/fastPRNG/fastPRNG.h"
 
 extern fastPRNG::fastXS64 xoshiro;
diff --git a/source/tx_forge.h b/source/tx_forge.h
index fde2bfdf6..fdb4f3675 100644
--- a/source/tx_forge.h
+++ b/source/tx_forge.h
@@ -2,14 +2,11 @@
 //  Spectral Synthesis (from ppmforge.c)
 //------------------------------------------------------------------------
 
-#ifndef __OBLIGE_TX_FORGE_H__
-#define __OBLIGE_TX_FORGE_H__
+#pragma once
 
 void TX_SpectralSynth(unsigned long long seed, float *buf, int width, double fracdim = 2.4, double powscale = 1.2);
 
 void TX_TestSynth(unsigned long long seed);
 
-#endif /* __OBLIGE_TX_FORGE_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/tx_skies.h b/source/tx_skies.h
index d08b61913..960899a39 100644
--- a/source/tx_skies.h
+++ b/source/tx_skies.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __OBLIGE_TX_SKIES_H__
-#define __OBLIGE_TX_SKIES_H__
+#pragma once
 
 #include <stdint.h>
 
@@ -39,7 +38,5 @@ void SKY_AddBuilding(unsigned long long seed, uint8_t *pixels, int W, int H, std
                      int width, int base_h, int top_h = 0, int win_prob = 50, int win_w = 2, int win_h = 2,
                      int antenna = 0);
 
-#endif /* __OBLIGE_TX_SKIES_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/ui_boxes.h b/source/ui_boxes.h
index 84499408b..9cdfbc8b9 100644
--- a/source/ui_boxes.h
+++ b/source/ui_boxes.h
@@ -1,5 +1,5 @@
-#ifndef OBSIDIAN_UI_BOXES_H_
-#define OBSIDIAN_UI_BOXES_H_
+#pragma once
+
 // Headers for custom FLTK box drawing routines so that Theme colors are honored
 // - Dasho
 
@@ -53,6 +53,4 @@ void cdown_box(int x, int y, int w, int h, Fl_Color c);
 void cengraved_frame(int x, int y, int w, int h, Fl_Color);
 void cengraved_box(int x, int y, int w, int h, Fl_Color c);
 void cembossed_frame(int x, int y, int w, int h, Fl_Color);
-void cembossed_box(int x, int y, int w, int h, Fl_Color c);
-
-#endif
+void cembossed_box(int x, int y, int w, int h, Fl_Color c);
\ No newline at end of file
diff --git a/source/ui_build.h b/source/ui_build.h
index 74b5e8c4a..1fd82c5c8 100644
--- a/source/ui_build.h
+++ b/source/ui_build.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __UI_BUILD_H__
-#define __UI_BUILD_H__
+#pragma once
 
 #include <string>
 #include <vector>
@@ -76,7 +75,5 @@ class UI_Build : public Fl_Group
     int FindStep(std::string name); // -1 if not found
 };
 
-#endif                              /* __UI_BUILD_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/ui_game.h b/source/ui_game.h
index 07b3c54e8..f3f4fb645 100644
--- a/source/ui_game.h
+++ b/source/ui_game.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __UI_GAME_H__
-#define __UI_GAME_H__
+#pragma once
 
 #include <cstddef>
 
@@ -75,7 +74,5 @@ class UI_Game : public Fl_Group
     static void quit_callback(Fl_Widget *, void *);
 };
 
-#endif /* __UI_GAME_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/ui_hyper.h b/source/ui_hyper.h
index 9da97ec3d..868fb505e 100644
--- a/source/ui_hyper.h
+++ b/source/ui_hyper.h
@@ -20,8 +20,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __UI_HYPER_H__
-#define __UI_HYPER_H__
+#pragma once
 
 #include <FL/Fl_Button.H>
 
@@ -75,7 +74,5 @@ class UI_ModHyperLink : public Fl_Button
     static void callback_Link(Fl_Widget *w, void *data);
 };
 
-#endif /* __UI_HYPER_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/ui_map.h b/source/ui_map.h
index 2afffcf6f..37b41834a 100644
--- a/source/ui_map.h
+++ b/source/ui_map.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __UI_MAP_H__
-#define __UI_MAP_H__
+#pragma once
 
 #include <stdint.h>
 
@@ -92,7 +91,5 @@ class UI_MiniMap : public Fl_Box
     }
 };
 
-#endif /* __UI_MAP_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/ui_module.h b/source/ui_module.h
index d3f62616c..8b37782b2 100644
--- a/source/ui_module.h
+++ b/source/ui_module.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __UI_MODS_H__
-#define __UI_MODS_H__
+#pragma once
 
 #include <map>
 #include <string>
@@ -206,7 +205,5 @@ class UI_CustomTabs : public Fl_Tabs
   public:
 };
 
-#endif /* __UI_MODS_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/ui_widgets.h b/source/ui_widgets.h
index 94d0f8a6e..688042977 100644
--- a/source/ui_widgets.h
+++ b/source/ui_widgets.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __UI_WIDGETS_H__
-#define __UI_WIDGETS_H__
+#pragma once
 
 #include <map>
 #include <string>
@@ -405,7 +404,5 @@ class UI_Clippy : public Fl_Double_Window
     int yoff;
 };
 
-#endif /* __UI_WIDGETS_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab
diff --git a/source/ui_window.h b/source/ui_window.h
index 240fe6bb1..8c2bf050f 100644
--- a/source/ui_window.h
+++ b/source/ui_window.h
@@ -19,8 +19,7 @@
 //
 //------------------------------------------------------------------------
 
-#ifndef __UI_WINDOW_H__
-#define __UI_WINDOW_H__
+#pragma once
 
 #include "hdr_fltk.h"
 #include "ui_build.h"
@@ -78,7 +77,5 @@ class UI_MainWin : public Fl_Double_Window
 
 extern UI_MainWin *main_win;
 
-#endif /* __UI_WINDOW_H__ */
-
 //--- editor settings ---
 // vi:ts=4:sw=4:noexpandtab