diff --git a/Makefile b/Makefile
index 6f8951d378..52bfe1e93f 100644
--- a/Makefile
+++ b/Makefile
@@ -41,11 +41,16 @@ REVISION     := 0
 TEST         ?= 0
 ANALYZE      ?= 0
 UNUSED_ERROR ?= 0
+DEBUG        ?= 0
 
 ifeq (check,$(MAKECMDGOALS))
   TEST := 1
 endif
 
+ifeq (debug,$(MAKECMDGOALS))
+  DEBUG := 1
+endif
+
 CPP := $(PREFIX)cpp
 
 ROM_NAME := pokeemerald.gba
@@ -60,6 +65,7 @@ MAP = $(ROM:.gba=.map)
 SYM = $(ROM:.gba=.sym)
 
 TEST_OBJ_DIR_NAME := build/modern-test
+DEBUG_OBJ_DIR_NAME := build/modern-debug
 
 TESTELF = $(ROM:.gba=-test.elf)
 HEADLESSELF = $(ROM:.gba=-test-headless.elf)
@@ -86,7 +92,8 @@ TEST_BUILDDIR = $(OBJ_DIR)/$(TEST_SUBDIR)
 ASFLAGS := -mcpu=arm7tdmi --defsym MODERN=1
 
 CC1              = $(shell $(PATH_ARMCC) --print-prog-name=cc1) -quiet
-override CFLAGS += -mthumb -mthumb-interwork -O2 -mabi=apcs-gnu -mtune=arm7tdmi -march=armv4t -fno-toplevel-reorder -Wno-pointer-to-int-cast -std=gnu17 -Werror -Wall -Wno-strict-aliasing -Wno-attribute-alias -Woverride-init
+override CFLAGS += -mthumb -mthumb-interwork -mabi=apcs-gnu -mtune=arm7tdmi -march=armv4t -fno-toplevel-reorder -Wno-pointer-to-int-cast -std=gnu17 -Werror -Wall -Wno-strict-aliasing -Wno-attribute-alias -Woverride-init
+
 ifeq ($(ANALYZE),1)
 override CFLAGS += -fanalyzer
 endif
@@ -101,6 +108,12 @@ OBJ_DIR := $(OBJ_DIR_NAME)
 LIBPATH := -L "$(dir $(shell $(PATH_ARMCC) -mthumb -print-file-name=libgcc.a))" -L "$(dir $(shell $(PATH_ARMCC) -mthumb -print-file-name=libnosys.a))" -L "$(dir $(shell $(PATH_ARMCC) -mthumb -print-file-name=libc.a))"
 LIB := $(LIBPATH) -lc -lnosys -lgcc -L../../libagbsyscall -lagbsyscall
 
+ifeq ($(DEBUG),1)
+override CFLAGS += -Og -g
+else
+override CFLAGS += -O2
+endif
+
 ifeq ($(TESTELF),$(MAKECMDGOALS))
   TEST := 1
 endif
@@ -108,6 +121,10 @@ endif
 ifeq ($(TEST),1)
 OBJ_DIR := $(TEST_OBJ_DIR_NAME)
 endif
+ifeq ($(DEBUG),1)
+OBJ_DIR := $(DEBUG_OBJ_DIR_NAME)
+endif
+
 
 CPPFLAGS := -iquote include -iquote $(GFLIB_SUBDIR) -Wno-trigraphs -DMODERN=1 -DTESTING=$(TEST)
 
@@ -146,7 +163,7 @@ MAKEFLAGS += --no-print-directory
 # Secondary expansion is required for dependency variables in object rules.
 .SECONDEXPANSION:
 
-.PHONY: all rom clean compare tidy tools check-tools mostlyclean clean-tools clean-check-tools $(TOOLDIRS) $(CHECKTOOLDIRS) libagbsyscall agbcc modern tidymodern tidynonmodern check history
+.PHONY: all rom clean compare tidy tools check-tools mostlyclean clean-tools clean-check-tools $(TOOLDIRS) $(CHECKTOOLDIRS) libagbsyscall agbcc modern tidymodern tidynonmodern check history debug
 
 infoshell = $(foreach line, $(shell $1 | sed "s/ /__SPACE__/g"), $(info $(subst __SPACE__, ,$(line))))
 
@@ -154,7 +171,7 @@ infoshell = $(foreach line, $(shell $1 | sed "s/ /__SPACE__/g"), $(info $(subst
 # Disable dependency scanning for clean/tidy/tools
 # Use a separate minimal makefile for speed
 # Since we don't need to reload most of this makefile
-ifeq (,$(filter-out all rom compare agbcc modern check libagbsyscall syms $(TESTELF),$(MAKECMDGOALS)))
+ifeq (,$(filter-out all rom compare agbcc modern check libagbsyscall syms $(TESTELF) debug,$(MAKECMDGOALS)))
 $(call infoshell, $(MAKE) -f make_tools.mk)
 else
 NODEP ?= 1
@@ -246,7 +263,7 @@ clean-tools:
 clean-check-tools:
 	@$(foreach tooldir,$(CHECKTOOLDIRS),$(MAKE) clean -C $(tooldir);)
 
-mostlyclean: tidynonmodern tidymodern tidycheck
+mostlyclean: tidynonmodern tidymodern tidycheck tidydebug
 	find sound -iname '*.bin' -exec rm {} +
 	rm -f $(MID_SUBDIR)/*.s
 	find . \( -iname '*.1bpp' -o -iname '*.4bpp' -o -iname '*.8bpp' -o -iname '*.gbapal' -o -iname '*.lz' -o -iname '*.rl' -o -iname '*.latfont' -o -iname '*.hwjpnfont' -o -iname '*.fwjpnfont' \) -exec rm {} +
@@ -256,7 +273,7 @@ mostlyclean: tidynonmodern tidymodern tidycheck
 	rm -f $(AUTO_GEN_TARGETS)
 	@$(MAKE) clean -C libagbsyscall
 
-tidy: tidymodern tidycheck
+tidy: tidymodern tidycheck tidydebug
 
 tidymodern:
 	rm -f $(ROM_NAME) $(ELF_NAME) $(MAP_NAME)
@@ -266,6 +283,8 @@ tidycheck:
 	rm -f $(TESTELF) $(HEADLESSELF)
 	rm -rf $(TEST_OBJ_DIR_NAME)
 
+tidydebug:
+	rm -rf $(DEBUG_OBJ_DIR_NAME)
 
 include graphics_file_rules.mk
 include map_data_rules.mk
@@ -305,6 +324,11 @@ ifeq ($(DINFO),1)
 override CFLAGS += -g
 endif
 
+ifeq ($(NOOPT),1)
+override CFLAGS := $(filter-out -O1 -Og -O2,$(CFLAGS))
+override CFLAGS += -O0
+endif
+
 # The dep rules have to be explicit or else missing files won't be reported.
 # As a side effect, they're evaluated immediately instead of when the rule is invoked.
 # It doesn't look like $(shell) can be deferred so there might not be a better way.
@@ -443,6 +467,8 @@ agbcc:
 
 modern: all
 
+debug: all
+
 LD_SCRIPT_TEST := ld_script_test.ld
 
 $(OBJ_DIR)/ld_script_test.ld: $(LD_SCRIPT_TEST) $(LD_SCRIPT_DEPS)
diff --git a/data/scripts/debug.inc b/data/scripts/debug.inc
index 12dc693fd0..4851c87c40 100644
--- a/data/scripts/debug.inc
+++ b/data/scripts/debug.inc
@@ -1,4 +1,3 @@
-.if DEBUG_OVERWORLD_MENU == TRUE
 Debug_MessageEnd:
 	waitmessage
 	waitbuttonpress
@@ -448,5 +447,3 @@ Debug_EventScript_EWRAMCounters::
 Debug_EventScript_EWRAMCounters_Text::
 	.string "Follower Steps: {STR_VAR_1}.\n"
 	.string "Fishing Chain: {STR_VAR_2}.$"
-
-.endif
diff --git a/src/battle_ai_main.c b/src/battle_ai_main.c
index ffaa058a08..f554da437d 100644
--- a/src/battle_ai_main.c
+++ b/src/battle_ai_main.c
@@ -196,14 +196,12 @@ void BattleAI_SetupFlags(void)
     else
         AI_THINKING_STRUCT->aiFlags[B_POSITION_PLAYER_LEFT] = 0; // player has no AI
 
-#if DEBUG_OVERWORLD_MENU == TRUE
-    if (gIsDebugBattle)
+    if (DEBUG_OVERWORLD_MENU && gIsDebugBattle)
     {
         AI_THINKING_STRUCT->aiFlags[B_POSITION_OPPONENT_LEFT] = gDebugAIFlags;
         AI_THINKING_STRUCT->aiFlags[B_POSITION_OPPONENT_RIGHT] = gDebugAIFlags;
         return;
     }
-#endif
 
     if (IsWildMonSmart() && !(gBattleTypeFlags & (BATTLE_TYPE_LINK | BATTLE_TYPE_TRAINER)))
     {
diff --git a/src/battle_main.c b/src/battle_main.c
index 319c26bcfa..c77c325db2 100644
--- a/src/battle_main.c
+++ b/src/battle_main.c
@@ -517,9 +517,7 @@ static void CB2_InitBattleInternal(void)
     gBattle_BG3_X = 0;
     gBattle_BG3_Y = 0;
 
-#if DEBUG_OVERWORLD_MENU == TRUE
-    if (!gIsDebugBattle)
-#endif
+    if (!DEBUG_OVERWORLD_MENU || (DEBUG_OVERWORLD_MENU && !gIsDebugBattle))
     {
         gBattleTerrain = BattleSetup_GetTerrainId();
     }
@@ -552,9 +550,7 @@ static void CB2_InitBattleInternal(void)
     else
         SetMainCallback2(CB2_HandleStartBattle);
 
-#if DEBUG_OVERWORLD_MENU == TRUE
-    if (!gIsDebugBattle)
-#endif
+    if (!DEBUG_OVERWORLD_MENU || (DEBUG_OVERWORLD_MENU && !gIsDebugBattle))
     {
         if (!(gBattleTypeFlags & (BATTLE_TYPE_LINK | BATTLE_TYPE_RECORDED)))
         {
diff --git a/src/debug.c b/src/debug.c
index a2bf55d95a..a3978fbd40 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -68,7 +68,6 @@
 #include "constants/weather.h"
 #include "save.h"
 
-#if DEBUG_OVERWORLD_MENU == TRUE
 // *******************************
 enum DebugMenu
 {
@@ -5129,5 +5128,3 @@ static void DebugAction_Util_CheckEWRAMCounters(u8 taskId)
 {
     Debug_DestroyMenu_Full_Script(taskId, Debug_EventScript_EWRAMCounters);
 }
-
-#endif //DEBUG_OVERWORLD_MENU == TRUE
diff --git a/src/field_control_avatar.c b/src/field_control_avatar.c
index 582617d555..9452e1273e 100644
--- a/src/field_control_avatar.c
+++ b/src/field_control_avatar.c
@@ -135,13 +135,14 @@ void FieldGetPlayerInput(struct FieldInput *input, u16 newKeys, u16 heldKeys)
     else if (heldKeys & DPAD_RIGHT)
         input->dpadDirection = DIR_EAST;
 
-#if DEBUG_OVERWORLD_MENU == TRUE && DEBUG_OVERWORLD_IN_MENU == FALSE
-    if ((heldKeys & DEBUG_OVERWORLD_HELD_KEYS) && input->DEBUG_OVERWORLD_TRIGGER_EVENT)
+    if(DEBUG_OVERWORLD_MENU && !DEBUG_OVERWORLD_IN_MENU)
     {
-        input->input_field_1_2 = TRUE;
-        input->DEBUG_OVERWORLD_TRIGGER_EVENT = FALSE;
+        if ((heldKeys & DEBUG_OVERWORLD_HELD_KEYS) && input->DEBUG_OVERWORLD_TRIGGER_EVENT)
+        {
+            input->input_field_1_2 = TRUE;
+            input->DEBUG_OVERWORLD_TRIGGER_EVENT = FALSE;
+        }
     }
-#endif
 }
 
 int ProcessPlayerFieldInput(struct FieldInput *input)
@@ -201,15 +202,13 @@ int ProcessPlayerFieldInput(struct FieldInput *input)
     if (input->pressedSelectButton && UseRegisteredKeyItemOnField() == TRUE)
         return TRUE;
 
-#if DEBUG_OVERWORLD_MENU == TRUE && DEBUG_OVERWORLD_IN_MENU == FALSE
-    if (input->input_field_1_2)
+    if(input->input_field_1_2 && DEBUG_OVERWORLD_MENU && !DEBUG_OVERWORLD_IN_MENU)
     {
         PlaySE(SE_WIN_OPEN);
         FreezeObjectEvents();
         Debug_ShowMainMenu();
         return TRUE;
     }
-#endif
 
     return FALSE;
 }
diff --git a/src/librfu_rfu.c b/src/librfu_rfu.c
index 152bb716e9..cd7cb6cc5a 100644
--- a/src/librfu_rfu.c
+++ b/src/librfu_rfu.c
@@ -762,7 +762,7 @@ static void rfu_CB_pollConnectParent(u8 reqCommand, u16 reqResult)
     u16 id;
     u8 slot;
     u8 bm_slot_flag, i;
-    struct RfuTgtData *target_p;
+    struct RfuTgtData *target_p = NULL;
     struct RfuTgtData target_local;
 
     if (reqResult == 0)
diff --git a/src/pokemon_sprite_visualizer.c b/src/pokemon_sprite_visualizer.c
index c83716aeda..a0b7ddabc2 100644
--- a/src/pokemon_sprite_visualizer.c
+++ b/src/pokemon_sprite_visualizer.c
@@ -41,7 +41,6 @@
 #include "constants/items.h"
 #include "constants/event_objects.h"
 
-#if DEBUG_POKEMON_SPRITE_VISUALIZER == TRUE
 extern const struct BattleBackground sBattleTerrainTable[];
 extern const struct CompressedSpriteSheet gSpriteSheet_EnemyShadow;
 extern const struct SpriteTemplate gSpriteTemplate_EnemyShadow;
@@ -1763,5 +1762,3 @@ static void Exit_PokemonSpriteVisualizer(u8 taskId)
         m4aMPlayVolumeControl(&gMPlayInfo_BGM, TRACKS_ALL, 0x100);
     }
 }
-
-#endif
diff --git a/src/pokemon_summary_screen.c b/src/pokemon_summary_screen.c
index a1ebc2b188..bf6ab45a2a 100644
--- a/src/pokemon_summary_screen.c
+++ b/src/pokemon_summary_screen.c
@@ -1640,15 +1640,13 @@ static void Task_HandleInput(u8 taskId)
             PlaySE(SE_SELECT);
             BeginCloseSummaryScreen(taskId);
         }
-    #if DEBUG_POKEMON_SPRITE_VISUALIZER == TRUE
-        else if (JOY_NEW(SELECT_BUTTON) && !gMain.inBattle)
+        else if (DEBUG_POKEMON_SPRITE_VISUALIZER && JOY_NEW(SELECT_BUTTON) && !gMain.inBattle)
         {
             sMonSummaryScreen->callback = CB2_Pokemon_Sprite_Visualizer;
             StopPokemonAnimations();
             PlaySE(SE_SELECT);
             CloseSummaryScreen(taskId);
         }
-    #endif
     }
 }
 
diff --git a/src/start_menu.c b/src/start_menu.c
index 0525ccf70d..71ab87363c 100644
--- a/src/start_menu.c
+++ b/src/start_menu.c
@@ -784,10 +784,11 @@ static bool8 StartMenuDebugCallback(void)
     RemoveExtraStartMenuWindows();
     HideStartMenuDebug(); // Hide start menu without enabling movement
 
-#if DEBUG_OVERWORLD_MENU == TRUE
-    FreezeObjectEvents();
-    Debug_ShowMainMenu();
-#endif
+    if (DEBUG_OVERWORLD_MENU)
+    {
+        FreezeObjectEvents();
+        Debug_ShowMainMenu();
+    }
 
 return TRUE;
 }