diff --git a/build.c b/build.c
index f1105827..957096a9 100644
--- a/build.c
+++ b/build.c
@@ -442,7 +442,7 @@ void OnBuild(StringList cli_args)
     D_Tag res_dir = D_TagFromPath(&perm, Lit("res"), D_TagKind_Dir);
     D_Tag icon_file = D_TagFromPath(&perm, Lit("icon.ico"), D_TagKind_File);
 
-    D_Tag inc_src_file = D_TagFromPath(&perm, Lit("src/inc.c"), D_TagKind_File);
+    D_Tag inc_src_file = D_TagFromPath(&perm, Lit("src/inc/inc_core.c"), D_TagKind_File);
     D_Tag rc_res_file = D_TagFromPath(&perm, StringF(&perm, Lit("%F/rc.res"), FmtStr(out_obj_dir_path)), D_TagKind_File);
 
     /* ========================== *
@@ -496,7 +496,6 @@ void OnBuild(StringList cli_args)
                                  "-fno-strict-aliasing "
                                  "-fno-finite-loops "
                                  "-fwrapv "
-                                 "-I src/ "
                                  "-msse4.1 "
                                  "-msse4.2 "));
 
@@ -962,14 +961,30 @@ void OnBuild(StringList cli_args)
 
             D_GetDirContents(&perm, &src_files, src_dir, 0);
             D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/base/base.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/prof/prof.cpp"), D_TagKind_File));
             D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/sys/sys.c"), D_TagKind_File));
             D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/gp/gp.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/resource/resource.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/watch/watch.c"), D_TagKind_File));
             D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/tar/tar.c"), D_TagKind_File));
             D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/ase/ase.c"), D_TagKind_File));
             D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/mp3/mp3.c"), D_TagKind_File));
             D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/json/json.c"), D_TagKind_File));
             D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/ttf/ttf.cpp"), D_TagKind_File));
             D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/dxc/dxc.cpp"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/sprite/sprite.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/font/font.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/sound/sound.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/draw/draw.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/inc/inc.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/host/host.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/asset_cache/asset_cache.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/mixer/mixer.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/settings/settings.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/space/space.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/collider/collider.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/app/app.c"), D_TagKind_File));
+            D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/playback/playback.c"), D_TagKind_File));
             D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/sim/sim.c"), D_TagKind_File));
             D_TagListAppend(&perm, &src_files, D_TagFromPath(&perm, Lit("src/user/user.c"), D_TagKind_File));
 
@@ -993,7 +1008,7 @@ void OnBuild(StringList cli_args)
                         if (PlatformWindows) {
                             ignore = !(StringEqual(name, Lit("sys_win32.c")) ||
                                        StringEqual(name, Lit("gp_dx12.c")) ||
-                                       StringEqual(name, Lit("playback_wasapi.c")) ||
+                                       StringEqual(name, Lit("playback_win32.c")) ||
                                        StringEqual(name, Lit("mp3_mmf.c")) ||
                                        StringEqual(name, Lit("ttf_dwrite.cpp")) ||
                                        StringEqual(name, Lit("dxc.cpp")));
diff --git a/src/app/app.c b/src/app/app.c
new file mode 100644
index 00000000..48498f5a
--- /dev/null
+++ b/src/app/app.c
@@ -0,0 +1,3 @@
+#include "app.h"
+
+#include "app_core.c"
diff --git a/src/app/app.h b/src/app/app.h
new file mode 100644
index 00000000..30635e04
--- /dev/null
+++ b/src/app/app.h
@@ -0,0 +1,24 @@
+#ifndef APP_H
+#define APP_H
+
+#include "../base/base.h"
+#include "../sys/sys.h"
+#include "../ttf/ttf.h"
+#include "../gp/gp.h"
+#include "../sim/sim.h"
+#include "../user/user.h"
+#include "../sprite/sprite.h"
+#include "../watch/watch.h"
+#include "../draw/draw.h"
+#include "../sound/sound.h"
+#include "../font/font.h"
+#include "../asset_cache/asset_cache.h"
+#include "../mixer/mixer.h"
+#include "../settings/settings.h"
+#include "../host/host.h"
+#include "../resource/resource.h"
+#include "../playback/playback.h"
+
+#include "app_core.h"
+
+#endif
diff --git a/src/app.c b/src/app/app_core.c
similarity index 96%
rename from src/app.c
rename to src/app/app_core.c
index a7253745..80c457c8 100644
--- a/src/app.c
+++ b/src/app/app_core.c
@@ -1,22 +1,3 @@
-#include "app.h"
-#include "base/base.h"
-#include "sys/sys.h"
-#include "ttf/ttf.h"
-#include "gp/gp.h"
-#include "sim/sim.h"
-#include "user/user.h"
-#include "playback.h"
-#include "resource.h"
-#include "asset_cache.h"
-#include "font.h"
-#include "sprite.h"
-#include "mixer.h"
-#include "sound.h"
-#include "settings.h"
-#include "draw.h"
-#include "host.h"
-#include "watch.h"
-
 GLOBAL struct {
     struct arena *arena;
     struct string write_path;
diff --git a/src/app.h b/src/app/app_core.h
similarity index 68%
rename from src/app.h
rename to src/app/app_core.h
index b178288e..bfbf7cbe 100644
--- a/src/app.h
+++ b/src/app/app_core.h
@@ -1,6 +1 @@
-#ifndef APP_H
-#define APP_H
-
 struct string app_write_path_cat(struct arena *arena, struct string filename);
-
-#endif
diff --git a/src/asset_cache/asset_cache.c b/src/asset_cache/asset_cache.c
new file mode 100644
index 00000000..bbf567ec
--- /dev/null
+++ b/src/asset_cache/asset_cache.c
@@ -0,0 +1,3 @@
+#include "asset_cache.h"
+
+#include "asset_cache_core.c"
diff --git a/src/asset_cache/asset_cache.h b/src/asset_cache/asset_cache.h
new file mode 100644
index 00000000..986277bd
--- /dev/null
+++ b/src/asset_cache/asset_cache.h
@@ -0,0 +1,9 @@
+#ifndef ASSET_CACHE_H
+#define ASSET_CACHE_H
+
+#include "../base/base.h"
+#include "../sys/sys.h"
+
+#include "asset_cache_core.h"
+
+#endif
diff --git a/src/asset_cache.c b/src/asset_cache/asset_cache_core.c
similarity index 98%
rename from src/asset_cache.c
rename to src/asset_cache/asset_cache_core.c
index a4398585..7fc6b1c1 100644
--- a/src/asset_cache.c
+++ b/src/asset_cache/asset_cache_core.c
@@ -1,7 +1,3 @@
-#include "asset_cache.h"
-#include "base/base.h"
-#include "sys/sys.h"
-
 /* ========================== *
  * Global state
  * ========================== */
diff --git a/src/asset_cache.h b/src/asset_cache/asset_cache_core.h
similarity index 91%
rename from src/asset_cache.h
rename to src/asset_cache/asset_cache_core.h
index d8ae7e9c..8e434950 100644
--- a/src/asset_cache.h
+++ b/src/asset_cache/asset_cache_core.h
@@ -1,9 +1,3 @@
-#ifndef ASSET_CACHE_H
-#define ASSET_CACHE_H
-
-#include "base/base.h"
-#include "sys/sys.h"
-
 enum asset_status {
     ASSET_STATUS_NONE,
 
@@ -49,5 +43,3 @@ struct asset_cache_store asset_cache_store_open(void);
 void asset_cache_store_close(struct asset_cache_store *store);
 
 u64 asset_cache_hash(struct string key);
-
-#endif
diff --git a/src/base/base.c b/src/base/base.c
index e03020d9..5a9298df 100644
--- a/src/base/base.c
+++ b/src/base/base.c
@@ -2,8 +2,9 @@
 
 #include "base_fiber.c"
 #include "base_arena.c"
-#include "base_buddy.c"
+#include "base_gstat.c"
 #include "base_memory.c"
+#include "base_buddy.c"
 #include "base_rand.c"
 #include "base_string.c"
 #include "base_bitbuff.c"
diff --git a/src/base/base.h b/src/base/base.h
index 75e1b9f4..dc072a17 100644
--- a/src/base/base.h
+++ b/src/base/base.h
@@ -1,11 +1,12 @@
 #ifndef BASE_H
 #define BASE_H
 
-#include "../gstat.h"
+#include "../prof/prof.h"
 
 #include "base_intrinsics.h"
 #include "base_atomic.h"
 #include "base_fiber.h"
+#include "base_gstat.h"
 #include "base_memory.h"
 #include "base_arena.h"
 #include "base_buddy.h"
diff --git a/src/gstat.c b/src/base/base_gstat.c
similarity index 73%
rename from src/gstat.c
rename to src/base/base_gstat.c
index 6cb0199e..9d33c4ba 100644
--- a/src/gstat.c
+++ b/src/base/base_gstat.c
@@ -1,5 +1,3 @@
-#include "gstat.h"
-
 #if GSTAT_ENABLED
 struct _gstats _g_gstats = ZI;
 #endif
diff --git a/src/gstat.h b/src/base/base_gstat.h
similarity index 91%
rename from src/gstat.h
rename to src/base/base_gstat.h
index 1cceffdc..035617e6 100644
--- a/src/gstat.h
+++ b/src/base/base_gstat.h
@@ -1,12 +1,7 @@
-#ifndef GSTAT_H
-#define GSTAT_H
-
 /* Program-wide statistics */
 
 #if GSTAT_ENABLED
 
-#include "base/base.h"
-
 struct _gstats {
     struct atomic64_padded GSTAT_SOCK_BYTES_SENT;
     struct atomic64_padded GSTAT_SOCK_BYTES_RECEIVED;
@@ -30,6 +25,3 @@ extern struct _gstats _g_gstats;
 #define gstat_get(name) 0
 
 #endif
-
-
-#endif
diff --git a/src/collider/collider.c b/src/collider/collider.c
new file mode 100644
index 00000000..af2f721b
--- /dev/null
+++ b/src/collider/collider.c
@@ -0,0 +1,3 @@
+#include "collider.h"
+
+#include "collider_core.c"
diff --git a/src/collider/collider.h b/src/collider/collider.h
new file mode 100644
index 00000000..65fe51e5
--- /dev/null
+++ b/src/collider/collider.h
@@ -0,0 +1,8 @@
+#ifndef COLLIDER_H
+#define COLLIDER_H
+
+#include "../base/base.h"
+
+#include "collider_core.h"
+
+#endif
diff --git a/src/collider.c b/src/collider/collider_core.c
similarity index 99%
rename from src/collider.c
rename to src/collider/collider_core.c
index 239ae0b6..587ff533 100644
--- a/src/collider.c
+++ b/src/collider/collider_core.c
@@ -1,7 +1,3 @@
-#include "collider.h"
-#include "base/base.h"
-#include "gstat.h"
-
 /* How close can non-overlapping shapes be before collision is considered */
 #define COLLISION_TOLERANCE     0.005f
 
diff --git a/src/collider.h b/src/collider/collider_core.h
similarity index 98%
rename from src/collider.h
rename to src/collider/collider_core.h
index 95d0f058..c751fefd 100644
--- a/src/collider.h
+++ b/src/collider/collider_core.h
@@ -1,6 +1,3 @@
-#ifndef COLLIDER_H
-#define COLLIDER_H
-
 struct collider_support_point {
     struct v2 p;
     u32 i;  /* Index of original point in shape */
@@ -70,5 +67,3 @@ f32 collider_time_of_impact(struct collider_shape *c0, struct collider_shape *c1
 
 struct v2_array menkowski(struct arena *arena, struct collider_shape *shape0, struct collider_shape *shape1, struct xform xf0, struct xform xf1, u32 detail);
 struct v2_array cloud(struct arena *arena, struct collider_shape *shape0, struct collider_shape *shape1, struct xform xf0, struct xform xf1);
-
-#endif
diff --git a/src/common.h b/src/common.h
index c4c57063..ef350747 100644
--- a/src/common.h
+++ b/src/common.h
@@ -680,17 +680,6 @@ INLINE f64 clamp_f64(f64 v, f64 min, f64 max) { return v < min ? min : v > max ?
 
 #include "config.h"
 
-/* ========================== *
- * Profiling
- * ========================== */
-
-#include "prof_tracy.h"
-
-#define PROF_THREAD_GROUP_FIBERS                -(i64)GIBI(1)
-#define PROF_THREAD_GROUP_SCHEDULER             -(i64)MEBI(3)
-#define PROF_THREAD_GROUP_WINDOW                -(i64)MEBI(2)
-#define PROF_THREAD_GROUP_MAIN                  -(i64)MEBI(1)
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/config.h b/src/config.h
index bb6667f2..9c7410fe 100644
--- a/src/config.h
+++ b/src/config.h
@@ -82,6 +82,11 @@
 /* If enabled, things like network writes & memory allocations will be tracked in a global statistics struct */
 #define GSTAT_ENABLED 1
 
+#define PROF_THREAD_GROUP_FIBERS                -(i64)GIBI(1)
+#define PROF_THREAD_GROUP_SCHEDULER             -(i64)MEBI(3)
+#define PROF_THREAD_GROUP_WINDOW                -(i64)MEBI(2)
+#define PROF_THREAD_GROUP_MAIN                  -(i64)MEBI(1)
+
 /* ========================== *
  * Settings
  * ========================== */
diff --git a/src/draw/draw.c b/src/draw/draw.c
new file mode 100644
index 00000000..857dc99d
--- /dev/null
+++ b/src/draw/draw.c
@@ -0,0 +1,3 @@
+#include "draw.h"
+
+#include "draw_core.c"
diff --git a/src/draw/draw.h b/src/draw/draw.h
new file mode 100644
index 00000000..691bb359
--- /dev/null
+++ b/src/draw/draw.h
@@ -0,0 +1,12 @@
+#ifndef DRAW_H
+#define DRAW_H
+
+#include "../base/base.h"
+#include "../gp/gp.h"
+#include "../sprite/sprite.h"
+#include "../font/font.h"
+#include "../collider/collider.h"
+
+#include "draw_core.h"
+
+#endif
diff --git a/src/draw.c b/src/draw/draw_core.c
similarity index 99%
rename from src/draw.c
rename to src/draw/draw_core.c
index fbea3c01..9cbc7bac 100644
--- a/src/draw.c
+++ b/src/draw/draw_core.c
@@ -1,9 +1,3 @@
-#include "draw.h"
-#include "base/base.h"
-#include "font.h"
-#include "sprite.h"
-#include "collider.h"
-
 GLOBAL struct {
     struct gp_resource *solid_white_texture;
 } G = ZI, DEBUG_ALIAS(G, G_draw);
diff --git a/src/draw.h b/src/draw/draw_core.h
similarity index 98%
rename from src/draw.h
rename to src/draw/draw_core.h
index cf36b7db..00703d81 100644
--- a/src/draw.h
+++ b/src/draw/draw_core.h
@@ -1,8 +1,3 @@
-#ifndef DRAW_H
-#define DRAW_H
-
-#include "gp/gp.h"
-
 struct font;
 struct font_startup_receipt;
 
@@ -138,5 +133,3 @@ struct draw_text_params {
 };
 
 struct rect draw_text(struct gp_render_sig *sig, struct draw_text_params params);
-
-#endif
diff --git a/src/font/font.c b/src/font/font.c
new file mode 100644
index 00000000..90ae31f5
--- /dev/null
+++ b/src/font/font.c
@@ -0,0 +1,3 @@
+#include "font.h"
+
+#include "font_core.c"
diff --git a/src/font/font.h b/src/font/font.h
new file mode 100644
index 00000000..dc745f33
--- /dev/null
+++ b/src/font/font.h
@@ -0,0 +1,12 @@
+#ifndef FONT_H
+#define FONT_H
+
+#include "../base/base.h"
+#include "../ttf/ttf.h"
+#include "../gp/gp.h"
+#include "../resource/resource.h"
+#include "../asset_cache/asset_cache.h"
+
+#include "font_core.h"
+
+#endif
diff --git a/src/font.c b/src/font/font_core.c
similarity index 98%
rename from src/font.c
rename to src/font/font_core.c
index 93eec2bf..60d098e0 100644
--- a/src/font.c
+++ b/src/font/font_core.c
@@ -1,10 +1,3 @@
-#include "font.h"
-#include "base/base.h"
-#include "ttf/ttf.h"
-#include "gp/gp.h"
-#include "asset_cache.h"
-#include "resource.h"
-
 #define LOOKUP_TABLE_SIZE (256)
 GLOBAL u32 g_font_codes[] = {
     0x20,0x21,0x22,0x23,0x24,0x25,0x26,0x27,0x28,0x29,0x2A,0x2B,0x2C,0x2D,0x2E,0x2F,0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39,0x3A,0x3B,0x3C,0x3D,0x3E,0x3F,0x40,0x41,0x42,0x43,0x44,0x45,0x46,0x47,0x48,0x49,0x4A,0x4B,0x4C,0x4D,0x4E,0x4F,0x50,0x51,0x52,0x53,0x54,0x55,0x56,0x57,0x58,0x59,0x5A,0x5B,0x5C,0x5D,0x5E,0x5F,0x60,0x61,0x62,0x63,0x64,0x65,0x66,0x67,0x68,0x69,0x6A,0x6B,0x6C,0x6D,0x6E,0x6F,0x70,0x71,0x72,0x73,0x74,0x75,0x76,0x77,0x78,0x79,0x7A,0x7B,0x7C,0x7D,0x7E,0x7F,0x80,0x81,0x82,0x83,0x84,0x85,0x86,0x87,0x88,0x89,0x8A,0x8B,0x8C,0x8D,0x8E,0x8F,0x90,0x91,0x92,0x93,0x94,0x95,0x96,0x97,0x98,0x99,0x9A,0x9B,0x9C,0x9D,0x9E,0x9F,0xA0,0xA1,0xA2,0xA3,0xA4,0xA5,0xA6,0xA7,0xA8,0xA9,0xAA,0xAB,0xAC,0xAD,0xAE,0xAF,0xB0,0xB1,0xB2,0xB3,0xB4,0xB5,0xB6,0xB7,0xB8,0xB9,0xBA,0xBB,0xBC,0xBD,0xBE,0xBF,0xC0,0xC1,0xC2,0xC3,0xC4,0xC5,0xC6,0xC7,0xC8,0xC9,0xCA,0xCB,0xCC,0xCD,0xCE,0xCF,0xD0,0xD1,0xD2,0xD3,0xD4,0xD5,0xD6,0xD7,0xD8,0xD9,0xDA,0xDB,0xDC,0xDD,0xDE,0xDF,0xE0,0xE1,0xE2,0xE3,0xE4,0xE5,0xE6,0xE7,0xE8,0xE9,0xEA,0xEB,0xEC,0xED,0xEE,0xEF,0xF0,0xF1,0xF2,0xF3,0xF4,0xF5,0xF6,0xF7,0xF8,0xF9,0xFA,0xFB,0xFC,0xFD,0xFE,0xFF
diff --git a/src/font.h b/src/font/font_core.h
similarity index 93%
rename from src/font.h
rename to src/font/font_core.h
index 4249e4c4..ad8bb9ee 100644
--- a/src/font.h
+++ b/src/font/font_core.h
@@ -1,8 +1,3 @@
-#ifndef FONT_H
-#define FONT_H
-
-#include "base/base.h"
-
 struct asset;
 struct asset_cache_startup_receipt;
 struct ttf_startup_receipt;
@@ -35,5 +30,3 @@ struct font *font_load_async(struct string path, f32 point_size);
 struct font *font_load(struct string path, f32 point_size);
 
 struct font_glyph *font_get_glyph(struct font *font, u32 codepoint);
-
-#endif
diff --git a/src/gp/gp.h b/src/gp/gp.h
index 5a264da0..5efd4495 100644
--- a/src/gp/gp.h
+++ b/src/gp/gp.h
@@ -6,6 +6,9 @@
 #include "../tar/tar.h"
 #include "../ase/ase.h"
 #include "../dxc/dxc.h"
+#include "../inc/inc.h"
+#include "../resource/resource.h"
+#include "../watch/watch.h"
 
 #include "gp_core.h"
 
diff --git a/src/gp/gp_core_dx12.c b/src/gp/gp_core_dx12.c
index 280cacd6..5ea4ef5d 100644
--- a/src/gp/gp_core_dx12.c
+++ b/src/gp/gp_core_dx12.c
@@ -1,8 +1,5 @@
-#include "../sprite.h"
-#include "../gstat.h"
-#include "../resource.h"
-#include "../inc.h"
-#include "../watch.h"
+/* TODO: Remove this */
+#include "../sprite/sprite.h"
 
 /* Include common shader types */
 #define SH_CPU 1
diff --git a/src/host/host.c b/src/host/host.c
new file mode 100644
index 00000000..55c45291
--- /dev/null
+++ b/src/host/host.c
@@ -0,0 +1,3 @@
+#include "host.h"
+
+#include "host_core.c"
diff --git a/src/host/host.h b/src/host/host.h
new file mode 100644
index 00000000..b45b2e48
--- /dev/null
+++ b/src/host/host.h
@@ -0,0 +1,9 @@
+#ifndef HOST_H
+#define HOST_H
+
+#include "../base/base.h"
+#include "../sys/sys.h"
+
+#include "host_core.h"
+
+#endif
diff --git a/src/host.c b/src/host/host_core.c
similarity index 99%
rename from src/host.c
rename to src/host/host_core.c
index fccaef09..6cecff1e 100644
--- a/src/host.c
+++ b/src/host/host_core.c
@@ -1,7 +1,3 @@
-#include "host.h"
-#include "base/base.h"
-#include "sys/sys.h"
-
 /* TODO:
  *
  * Rate limiting.
diff --git a/src/host.h b/src/host/host_core.h
similarity index 97%
rename from src/host.h
rename to src/host/host_core.h
index 09c7b4ba..6abe1135 100644
--- a/src/host.h
+++ b/src/host/host_core.h
@@ -1,9 +1,3 @@
-#ifndef HOST_H
-#define HOST_H
-
-#include "base/base.h"
-#include "sys/sys.h"
-
 #define HOST_CHANNEL_ID_NIL (struct host_channel_id) { .gen = 0, .idx = 0 }
 #define HOST_CHANNEL_ID_ALL (struct host_channel_id) { .gen = U32_MAX, .idx = U32_MAX }
 
@@ -137,5 +131,3 @@ INLINE b32 host_channel_id_is_nil(struct host_channel_id id) { return id.gen ==
 
 struct host_event_list host_update_begin(struct arena *arena, struct host *host);
 void host_update_end(struct host *host);
-
-#endif
diff --git a/src/inc/inc.c b/src/inc/inc.c
new file mode 100644
index 00000000..a89d040a
--- /dev/null
+++ b/src/inc/inc.c
@@ -0,0 +1,3 @@
+#include "inc.h"
+
+#include "inc_core.c"
diff --git a/src/inc/inc.h b/src/inc/inc.h
new file mode 100644
index 00000000..5a032d4c
--- /dev/null
+++ b/src/inc/inc.h
@@ -0,0 +1,8 @@
+#ifndef INC_H
+#define INC_H
+
+#include "../base/base.h"
+
+#include "inc_core.h"
+
+#endif
diff --git a/src/inc.c b/src/inc/inc_core.c
similarity index 92%
rename from src/inc.c
rename to src/inc/inc_core.c
index e183c53f..0e144a53 100644
--- a/src/inc.c
+++ b/src/inc/inc_core.c
@@ -1,6 +1,3 @@
-#include "inc.h"
-#include "base/base.h"
-
 /* This is the file that actually includes binary data meant to be embedded in
  * the executable. Embedded files should be added as dependencies to this source
  * file via the build system to ensure this translation unit is recompiled upon
diff --git a/src/inc.h b/src/inc/inc_core.h
similarity index 72%
rename from src/inc.h
rename to src/inc/inc_core.h
index c14138ed..e604ab46 100644
--- a/src/inc.h
+++ b/src/inc/inc_core.h
@@ -1,10 +1,5 @@
-#ifndef INC_H
-#define INC_H
-
 #if RESOURCES_EMBEDDED
 struct string inc_res_tar(void);
 #endif
 
 struct string inc_dxc_tar(void);
-
-#endif
diff --git a/src/mixer/mixer.c b/src/mixer/mixer.c
new file mode 100644
index 00000000..38b0235f
--- /dev/null
+++ b/src/mixer/mixer.c
@@ -0,0 +1,3 @@
+#include "mixer.h"
+
+#include "mixer_core.c"
diff --git a/src/mixer/mixer.h b/src/mixer/mixer.h
new file mode 100644
index 00000000..ce2ff76a
--- /dev/null
+++ b/src/mixer/mixer.h
@@ -0,0 +1,10 @@
+#ifndef MIXER_H
+#define MIXER_H
+
+#include "../base/base.h"
+#include "../sys/sys.h"
+#include "../sound/sound.h"
+
+#include "mixer_core.h"
+
+#endif
diff --git a/src/mixer.c b/src/mixer/mixer_core.c
similarity index 99%
rename from src/mixer.c
rename to src/mixer/mixer_core.c
index bcdd6116..82f8f52c 100644
--- a/src/mixer.c
+++ b/src/mixer/mixer_core.c
@@ -1,8 +1,3 @@
-#include "mixer.h"
-#include "base/base.h"
-#include "sys/sys.h"
-#include "sound.h"
-
 /* TODO: Cap max sounds playing. */
 
 /* Terminology:
diff --git a/src/mixer.h b/src/mixer/mixer_core.h
similarity index 96%
rename from src/mixer.h
rename to src/mixer/mixer_core.h
index 73c8684d..61abe1d5 100644
--- a/src/mixer.h
+++ b/src/mixer/mixer_core.h
@@ -1,6 +1,3 @@
-#ifndef MIXER_H
-#define MIXER_H
-
 struct sound;
 
 #define MIXER_FLAG_NONE         0x0
@@ -50,5 +47,3 @@ void mixer_set_listener(struct v2 pos, struct v2 dir);
 
 /* Mixing */
 struct mixed_pcm_f32 mixer_update(struct arena *arena, u64 frame_request_count);
-
-#endif
diff --git a/src/playback/playback.c b/src/playback/playback.c
new file mode 100644
index 00000000..42af1243
--- /dev/null
+++ b/src/playback/playback.c
@@ -0,0 +1,7 @@
+#include "playback.h"
+
+#if PLATFORM_WINDOWS
+# include "playback_core_win32.c"
+#else
+# error Playback core not implemented for this platform
+#endif
diff --git a/src/playback/playback.h b/src/playback/playback.h
new file mode 100644
index 00000000..c3a7c2b0
--- /dev/null
+++ b/src/playback/playback.h
@@ -0,0 +1,10 @@
+#ifndef PLAYBACK_H
+#define PLAYBACK_H
+
+#include "../base/base.h"
+#include "../sys/sys.h"
+#include "../mixer/mixer.h"
+
+#include "playback_core.h"
+
+#endif
diff --git a/src/playback.h b/src/playback/playback_core.h
similarity index 77%
rename from src/playback.h
rename to src/playback/playback_core.h
index 12bae469..0d63f8bc 100644
--- a/src/playback.h
+++ b/src/playback/playback_core.h
@@ -1,9 +1,4 @@
-#ifndef PLAYBACK_H
-#define PLAYBACK_H
-
 struct mixer_startup_receipt;
 
 struct playback_startup_receipt { i32 _; };
 struct playback_startup_receipt playback_startup(struct mixer_startup_receipt *mixer_sr);
-
-#endif
diff --git a/src/playback_wasapi.c b/src/playback/playback_core_win32.c
similarity index 98%
rename from src/playback_wasapi.c
rename to src/playback/playback_core_win32.c
index 8e349e28..fad38683 100644
--- a/src/playback_wasapi.c
+++ b/src/playback/playback_core_win32.c
@@ -5,12 +5,6 @@
  * https://gist.github.com/mmozeiko/5a5b168e61aff4c1eaec0381da62808f#file-win32_wasapi-h
  * ========================== */
 
-#include "playback.h"
-#include "base/base.h"
-#include "sys/sys.h"
-#include "mixer.h"
-#include "app.h"
-
 #define COBJMACROS
 #define WIN32_LEAN_AND_MEAN
 #define UNICODE
diff --git a/src/prof/prof.cpp b/src/prof/prof.cpp
new file mode 100644
index 00000000..e04e5cc6
--- /dev/null
+++ b/src/prof/prof.cpp
@@ -0,0 +1,3 @@
+#include "prof.h"
+
+#include "prof_core_tracy.cpp"
diff --git a/src/prof/prof.h b/src/prof/prof.h
new file mode 100644
index 00000000..2e4f2206
--- /dev/null
+++ b/src/prof/prof.h
@@ -0,0 +1,6 @@
+#ifndef PROF_H
+#define PROF_H
+
+#include "prof_core_tracy.h"
+
+#endif
diff --git a/src/prof/prof_core_tracy.cpp b/src/prof/prof_core_tracy.cpp
new file mode 100644
index 00000000..e69de29b
diff --git a/src/prof_tracy.h b/src/prof/prof_core_tracy.h
similarity index 99%
rename from src/prof_tracy.h
rename to src/prof/prof_core_tracy.h
index 6582732e..977848d1 100644
--- a/src/prof_tracy.h
+++ b/src/prof/prof_core_tracy.h
@@ -1,6 +1,3 @@
-#ifndef PROF_H
-#define PROF_H
-
 #if PROFILING
 
 #if COMPILER_MSVC
@@ -153,5 +150,3 @@ FORCE_NO_INLINE INLINE void __prof_fiber_leave(void) { TracyCFiberLeave; }
 #  define __prof_fiber_enter(fiber_name, profiler_group)
 #  define __prof_fiber_leave()
 #endif
-
-#endif
diff --git a/src/prof_tracy.cpp b/src/prof_tracy.cpp
deleted file mode 100644
index aecad03b..00000000
--- a/src/prof_tracy.cpp
+++ /dev/null
@@ -1,9 +0,0 @@
-#if PROFILING
-
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Weverything"
-#define TRACY_FIBERS
-# include TRACY_CLIENT_SRC_PATH
-#pragma clang diagnostic pop
-
-#endif
diff --git a/src/resource/resource.c b/src/resource/resource.c
new file mode 100644
index 00000000..4e9714cb
--- /dev/null
+++ b/src/resource/resource.c
@@ -0,0 +1,3 @@
+#include "resource.h"
+
+#include "resource_core.c"
diff --git a/src/resource/resource.h b/src/resource/resource.h
new file mode 100644
index 00000000..cfa0df62
--- /dev/null
+++ b/src/resource/resource.h
@@ -0,0 +1,14 @@
+#ifndef RESOURCE_H
+#define RESOURCE_H
+
+#include "../base/base.h"
+#include "../sys/sys.h"
+#include "../tar/tar.h"
+
+#if RESOURCES_EMBEDDED
+# include "../inc/inc.h"
+#endif
+
+#include "resource_core.h"
+
+#endif
diff --git a/src/resource.c b/src/resource/resource_core.c
similarity index 94%
rename from src/resource.c
rename to src/resource/resource_core.c
index 4a0a06aa..7df10f85 100644
--- a/src/resource.c
+++ b/src/resource/resource_core.c
@@ -1,17 +1,7 @@
-#include "resource.h"
-#include "app.h"
-#include "base/base.h"
-#include "sys/sys.h"
-#include "tar/tar.h"
-
 /* ========================== *
  * Global data
  * ========================== */
 
-#if RESOURCES_EMBEDDED
-# include "inc.h"
-#endif
-
 /* Add resource data to binary */
 
 GLOBAL struct {
diff --git a/src/resource.h b/src/resource/resource_core.h
similarity index 94%
rename from src/resource.h
rename to src/resource/resource_core.h
index ec0cb974..7637dd73 100644
--- a/src/resource.h
+++ b/src/resource/resource_core.h
@@ -1,8 +1,3 @@
-#ifndef RESOURCE_H
-#define RESOURCE_H
-
-#include "sys/sys.h"
-
 #define RESOURCE_NAME_LEN_MAX 256
 
 /* A resource contains data that can be retrieved globally by name.
@@ -53,5 +48,3 @@ struct resource resource_open(struct string name);
 #else
     #define resource_get_name(res_ptr) STRING((res_ptr)->_name_len, (res_ptr)->_name_text)
 #endif
-
-#endif
diff --git a/src/settings/settings.c b/src/settings/settings.c
new file mode 100644
index 00000000..3e05f5c3
--- /dev/null
+++ b/src/settings/settings.c
@@ -0,0 +1,3 @@
+#include "settings.h"
+
+#include "settings_core.c"
diff --git a/src/settings/settings.h b/src/settings/settings.h
new file mode 100644
index 00000000..8ed9a898
--- /dev/null
+++ b/src/settings/settings.h
@@ -0,0 +1,10 @@
+#ifndef SETTINGS_H
+#define SETTINGS_H
+
+#include "../base/base.h"
+#include "../sys/sys.h"
+#include "../json/json.h"
+
+#include "settings_core.h"
+
+#endif
diff --git a/src/settings.c b/src/settings/settings_core.c
similarity index 98%
rename from src/settings.c
rename to src/settings/settings_core.c
index 4dcfebbf..928b2c5d 100644
--- a/src/settings.c
+++ b/src/settings/settings_core.c
@@ -1,8 +1,3 @@
-#include "settings.h"
-#include "base/base.h"
-#include "sys/sys.h"
-#include "json/json.h"
-
 struct string settings_serialize(struct arena *arena, const struct sys_window_settings *settings)
 {
     __prof;
diff --git a/src/settings.h b/src/settings/settings_core.h
similarity index 84%
rename from src/settings.h
rename to src/settings/settings_core.h
index 6af5532c..59d69cbe 100644
--- a/src/settings.h
+++ b/src/settings/settings_core.h
@@ -1,9 +1,5 @@
-#ifndef SETTINGS_H
-#define SETTINGS_H
-
 struct sys_window_settings;
 
 struct string settings_serialize(struct arena *arena, const struct sys_window_settings *settings);
-struct sys_window_settings *settings_deserialize(struct arena *arena, struct string src, struct string *error_out);
 
-#endif
+struct sys_window_settings *settings_deserialize(struct arena *arena, struct string src, struct string *error_out);
diff --git a/src/sim/sim.h b/src/sim/sim.h
index 43cfc7ca..943c4d7e 100644
--- a/src/sim/sim.h
+++ b/src/sim/sim.h
@@ -2,11 +2,11 @@
 #define SIM_H
 
 #include "../base/base.h"
-#include "../collider.h"
-#include "../sprite.h"
-#include "../space.h"
-#include "../host.h"
-#include "../mixer.h"
+#include "../sprite/sprite.h"
+#include "../collider/collider.h"
+#include "../space/space.h"
+#include "../host/host.h"
+#include "../mixer/mixer.h"
 
 #include "sim_core.h"
 #include "sim_phys.h"
diff --git a/src/sound/sound.c b/src/sound/sound.c
new file mode 100644
index 00000000..aa22fe9e
--- /dev/null
+++ b/src/sound/sound.c
@@ -0,0 +1,3 @@
+#include "sound.h"
+
+#include "sound_core.c"
diff --git a/src/sound/sound.h b/src/sound/sound.h
new file mode 100644
index 00000000..ef384e10
--- /dev/null
+++ b/src/sound/sound.h
@@ -0,0 +1,12 @@
+#ifndef SOUND_H
+#define SOUND_H
+
+#include "../base/base.h"
+#include "../sys/sys.h"
+#include "../mp3/mp3.h"
+#include "../resource/resource.h"
+#include "../asset_cache/asset_cache.h"
+
+#include "sound_core.h"
+
+#endif
diff --git a/src/sound.c b/src/sound/sound_core.c
similarity index 97%
rename from src/sound.c
rename to src/sound/sound_core.c
index 384dce97..90210950 100644
--- a/src/sound.c
+++ b/src/sound/sound_core.c
@@ -1,10 +1,3 @@
-#include "sound.h"
-#include "base/base.h"
-#include "sys/sys.h"
-#include "resource.h"
-#include "asset_cache.h"
-#include "mp3/mp3.h"
-
 #define SOUND_SAMPLE_RATE 48000
 
 struct sound_task_params {
diff --git a/src/sound.h b/src/sound/sound_core.h
similarity index 92%
rename from src/sound.h
rename to src/sound/sound_core.h
index ad00b820..865e5398 100644
--- a/src/sound.h
+++ b/src/sound/sound_core.h
@@ -1,6 +1,3 @@
-#ifndef SOUND_H
-#define SOUND_H
-
 #define SOUND_FLAG_NONE         0x0
 #define SOUND_FLAG_STEREO       0x1
 
@@ -18,5 +15,3 @@ struct sound_startup_receipt sound_startup(struct asset_cache_startup_receipt *a
 struct asset *sound_load_asset(struct string path, u32 flags, b32 wait);
 struct sound *sound_load_async(struct string path, u32 flags);
 struct sound *sound_load(struct string path, u32 flags);
-
-#endif
diff --git a/src/space/space.c b/src/space/space.c
new file mode 100644
index 00000000..2d6c673c
--- /dev/null
+++ b/src/space/space.c
@@ -0,0 +1,3 @@
+#include "space.h"
+
+#include "space_core.c"
diff --git a/src/space/space.h b/src/space/space.h
new file mode 100644
index 00000000..dff648e0
--- /dev/null
+++ b/src/space/space.h
@@ -0,0 +1,9 @@
+#ifndef SPACE_H
+#define SPACE_H
+
+#include "../base/base.h"
+#include "../collider/collider.h"
+
+#include "space_core.h"
+
+#endif
diff --git a/src/space.c b/src/space/space_core.c
similarity index 99%
rename from src/space.c
rename to src/space/space_core.c
index cbad7dea..b9948268 100644
--- a/src/space.c
+++ b/src/space/space_core.c
@@ -1,7 +1,3 @@
-#include "space.h"
-#include "base/base.h"
-#include "collider.h"
-
 /* FIXME: Default space entry & cell pointers to nil */
 
 /* Offset in bytes from start of space struct to start of entry array (assume adjacently allocated) */
diff --git a/src/space.h b/src/space/space_core.h
similarity index 98%
rename from src/space.h
rename to src/space/space_core.h
index 1cc4ac20..f04e5ae2 100644
--- a/src/space.h
+++ b/src/space/space_core.h
@@ -1,6 +1,3 @@
-#ifndef SPACE_H
-#define SPACE_H
-
 struct space_cell_bin;
 
 struct space_entry {
@@ -132,5 +129,3 @@ void space_entry_update_aabb(struct space_entry *entry, struct aabb new_aabb);
 struct space_iter space_iter_begin_aabb(struct space *space, struct aabb aabb);
 struct space_entry *space_iter_next(struct space_iter *iter);
 #define space_iter_end(i)
-
-#endif
diff --git a/src/sprite/sprite.c b/src/sprite/sprite.c
new file mode 100644
index 00000000..c1dca241
--- /dev/null
+++ b/src/sprite/sprite.c
@@ -0,0 +1,3 @@
+#include "sprite.h"
+
+#include "sprite_core.c"
diff --git a/src/sprite/sprite.h b/src/sprite/sprite.h
new file mode 100644
index 00000000..5c93ec56
--- /dev/null
+++ b/src/sprite/sprite.h
@@ -0,0 +1,13 @@
+#ifndef SPRITE_H
+#define SPRITE_H
+
+#include "../base/base.h"
+#include "../sys/sys.h"
+#include "../gp/gp.h"
+#include "../ase/ase.h"
+#include "../resource/resource.h"
+#include "../watch/watch.h"
+
+#include "sprite_core.h"
+
+#endif
diff --git a/src/sprite.c b/src/sprite/sprite_core.c
similarity index 99%
rename from src/sprite.c
rename to src/sprite/sprite_core.c
index 696d17a5..04791532 100644
--- a/src/sprite.c
+++ b/src/sprite/sprite_core.c
@@ -1,12 +1,3 @@
-#include "sprite.h"
-#include "base/base.h"
-#include "sys/sys.h"
-#include "ase/ase.h"
-#include "resource.h"
-#include "app.h"
-#include "gp/gp.h"
-#include "watch.h"
-
 /* The evictor will begin evicting once cache usage is > threshold.
  * It will entries until the budget has shrunk < target. */
 #define CACHE_MEMORY_BUDGET_THRESHOLD (MEBI(256))
diff --git a/src/sprite.h b/src/sprite/sprite_core.h
similarity index 98%
rename from src/sprite.h
rename to src/sprite/sprite_core.h
index 3b194b69..ce6b01db 100644
--- a/src/sprite.h
+++ b/src/sprite/sprite_core.h
@@ -1,8 +1,3 @@
-#ifndef SPRITE_H
-#define SPRITE_H
-
-#include "base/base.h"
-
 struct sprite_sheet_span;
 struct sprite_sheet_slice_group;
 
@@ -136,5 +131,3 @@ struct sprite_sheet_slice sprite_sheet_get_slice(struct sprite_sheet *sheet, str
 
 /* Returns all slices with name in frame */
 struct sprite_sheet_slice_array sprite_sheet_get_slices(struct sprite_sheet *sheet, struct string name, u32 frame_index);
-
-#endif
diff --git a/src/sys/sys.h b/src/sys/sys.h
index 048a6bd2..5fd71073 100644
--- a/src/sys/sys.h
+++ b/src/sys/sys.h
@@ -2,8 +2,6 @@
 #define SYS_H
 
 #include "../base/base.h"
-#include "../app.h"
-#include "../gstat.h"
 
 #include "sys_snc.h"
 #include "sys_sleep.h"
diff --git a/src/ttf/ttf_core_dwrite.cpp b/src/ttf/ttf_core_dwrite.cpp
index f514fc1b..7d4edf4e 100644
--- a/src/ttf/ttf_core_dwrite.cpp
+++ b/src/ttf/ttf_core_dwrite.cpp
@@ -3,7 +3,7 @@
 
 extern "C"
 {
-#include "../font.h"
+#include "../font/font.h"
 }
 
 #pragma warning(push, 0)
diff --git a/src/user/user.h b/src/user/user.h
index 3ecb1b64..351a60a8 100644
--- a/src/user/user.h
+++ b/src/user/user.h
@@ -3,6 +3,12 @@
 
 #include "../base/base.h"
 #include "../sim/sim.h"
+#include "../gp/gp.h"
+#include "../sprite/sprite.h"
+#include "../font/font.h"
+#include "../collider/collider.h"
+#include "../draw/draw.h"
+#include "../host/host.h"
 
 #include "user_core.h"
 
diff --git a/src/user/user_core.c b/src/user/user_core.c
index 2959ee43..ccdfad0d 100644
--- a/src/user/user_core.c
+++ b/src/user/user_core.c
@@ -1,18 +1,3 @@
-#include "user.h"
-#include "base/base.h"
-#include "sys/sys.h"
-#include "gp/gp.h"
-#include "sim/sim.h"
-#include "font.h"
-#include "sprite.h"
-#include "draw.h"
-#include "asset_cache.h"
-#include "mixer.h"
-#include "collider.h"
-#include "host.h"
-#include "gstat.h"
-#include "app.h"
-
 struct bind_state {
     b32 is_held;                    /* Is this bind held down this frame */
     u32 num_presses;                /* How many times was this bind's pressed since last frame */
diff --git a/src/user/user_core.h b/src/user/user_core.h
index 3bb6eecf..c30960b1 100644
--- a/src/user/user_core.h
+++ b/src/user/user_core.h
@@ -1,6 +1,3 @@
-#include "base/base.h"
-#include "sys/sys.h"
-
 struct font_startup_receipt;
 struct sprite_startup_receipt;
 struct draw_startup_receipt;
diff --git a/src/watch/watch.c b/src/watch/watch.c
new file mode 100644
index 00000000..d97ac3cd
--- /dev/null
+++ b/src/watch/watch.c
@@ -0,0 +1,3 @@
+#include "watch.h"
+
+#include "watch_core.c"
diff --git a/src/watch/watch.h b/src/watch/watch.h
new file mode 100644
index 00000000..885ffb44
--- /dev/null
+++ b/src/watch/watch.h
@@ -0,0 +1,9 @@
+#ifndef WATCH_H
+#define WATCH_H
+
+#include "../base/base.h"
+#include "../sys/sys.h"
+
+#include "watch_core.h"
+
+#endif
diff --git a/src/watch.c b/src/watch/watch_core.c
similarity index 99%
rename from src/watch.c
rename to src/watch/watch_core.c
index adaa68b9..819135d8 100644
--- a/src/watch.c
+++ b/src/watch/watch_core.c
@@ -1,10 +1,5 @@
-#include "watch.h"
-
 #if RESOURCE_RELOADING
 
-#include "base/base.h"
-#include "sys/sys.h"
-
 struct watch_event {
     struct string name;
     struct watch_event *next;
diff --git a/src/watch.h b/src/watch/watch_core.h
similarity index 88%
rename from src/watch.h
rename to src/watch/watch_core.h
index d116ada1..dbb0c477 100644
--- a/src/watch.h
+++ b/src/watch/watch_core.h
@@ -1,6 +1,3 @@
-#ifndef WATCH_H
-#define WATCH_H
-
 #define WATCH_CALLBACK_FUNC_DEF(func_name, arg_name) void func_name(struct string arg_name)
 typedef WATCH_CALLBACK_FUNC_DEF(watch_callback, name);
 
@@ -11,5 +8,3 @@ void watch_register_callback(watch_callback *callback);
 #else
 #define watch_register_callback(callback)
 #endif
-
-#endif