Tell people that their emulator sucks or their GBA is broken instead of just blinding them.

src/main.c

@@ -69,6 +69,8 @@ u8 gLinkVSyncDisabled;
 u32 IntrMain_Buffer[0x200];
 s8 gPcmDmaCounter;
 
+extern void CB2_FlashNotDetectedScreen(void); // for Crust's sake use mGBA, people!
+
 static EWRAM_DATA u16 gTrainerId = 0;
 
 //EWRAM_DATA void (**gFlashTimerIntrFunc)(void) = NULL;
@@ -114,7 +116,7 @@ void AgbMain()
     gSoftResetDisabled = FALSE;
 
     if (gFlashMemoryPresent != TRUE)
-        SetMainCallback2(NULL);
+        SetMainCallback2(CB2_FlashNotDetectedScreen);
 
     gLinkTransferringData = FALSE;
     sUnusedVar = 0xFC0;

src/save_failed_screen.c

@@ -401,3 +401,50 @@ static bool8 WipeSectors(u32 sectorBits)
     else
         return TRUE;
 }
+
+void CB2_FlashNotDetectedScreen(void){
+    static const struct WindowTemplate textWin[] = {
+        {
+            .bg = 0,
+            .tilemapLeft = 3,
+            .tilemapTop = 2,
+            .width = 24,
+            .height = 16,
+            .paletteNum = 15,
+            .baseBlock = 1,
+        }
+    };
+	
+    static const char errorMsg[] = _(
+        "{COLOR RED}Hey!\n"
+        "{COLOR DARK_GRAY}Flash memory not detected.\n\n"
+        "Please make sure you\nare playing the game\n"
+        "on the mGBA emu-\nlator"
+    );
+
+    if (!gMain.state){
+        SetGpuReg(REG_OFFSET_DISPCNT, 0);
+	SetGpuReg(REG_OFFSET_BLDCNT, 0);
+        SetGpuReg(REG_OFFSET_BG0CNT, 0);
+        SetGpuReg(REG_OFFSET_BG0HOFS, 0);
+        SetGpuReg(REG_OFFSET_BG0VOFS, 0);
+        DmaFill16(3, 0, VRAM, VRAM_SIZE);
+        DmaFill32(3, 0, OAM, OAM_SIZE);
+        DmaFill16(3, 0, PLTT, PLTT_SIZE);
+	ResetBgsAndClearDma3BusyFlags(0);
+        InitBgsFromTemplates(0, sBgTemplates, ARRAY_COUNT(sBgTemplates));
+        LoadBgTiles(0, gTextWindowFrame1_Gfx, 0x120, 0x214);
+        DeactivateAllTextPrinters();
+        ResetTasks();
+        ResetPaletteFade();
+	LoadPalette(gTextWindowFrame1_Pal, 0xE0, 0x20);
+        LoadPalette(gStandardMenuPalette, 0xF0, 0x20);
+	InitWindows(textWin);
+	DrawStdFrameWithCustomTileAndPalette(0, TRUE, 0x214, 0xE);
+        SaveFailedScreenTextPrint(errorMsg, 1, 0);
+	TransferPlttBuffer();
+	*(u16*)PLTT = RGB(17, 18, 31);
+	ShowBg(0);
+        gMain.state++;
+    }
+}