diff --git a/Imgui/CMakeLists.txt b/Imgui/CMakeLists.txt
index e91fa671..1a2ba556 100644
--- a/Imgui/CMakeLists.txt
+++ b/Imgui/CMakeLists.txt
@@ -5,6 +5,7 @@ project(Diligent-Imgui CXX)
 set(SOURCE
     src/ImGuiDiligentRenderer.cpp
     src/ImGuiImplDiligent.cpp
+    src/ImGuiDiligentFileIO.cpp
     src/ImGuiUtils.cpp
 )
 
@@ -126,7 +127,7 @@ if(PLATFORM_UNIVERSAL_WINDOWS)
     target_compile_definitions(Diligent-Imgui PRIVATE IMGUI_DISABLE_WIN32_FUNCTIONS)
 endif()
 
-target_compile_definitions(Diligent-Imgui PUBLIC IMGUI_DEFINE_MATH_OPERATORS)
+target_compile_definitions(Diligent-Imgui PUBLIC IMGUI_USER_CONFIG="ImGuiDiligentConfig.h")
 
 if(PLATFORM_WIN32 AND MINGW_BUILD)
     # Link with dwmapi.lib as imgui_impl_win32.cpp skips
diff --git a/Imgui/interface/ImGuiDiligentConfig.h b/Imgui/interface/ImGuiDiligentConfig.h
new file mode 100644
index 00000000..1c40de11
--- /dev/null
+++ b/Imgui/interface/ImGuiDiligentConfig.h
@@ -0,0 +1,58 @@
+/*
+ *  Copyright 2026 Diligent Graphics LLC
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  In no event and under no legal theory, whether in tort (including negligence),
+ *  contract, or otherwise, unless required by applicable law (such as deliberate
+ *  and grossly negligent acts) or agreed to in writing, shall any Contributor be
+ *  liable for any damages, including any direct, indirect, special, incidental,
+ *  or consequential damages of any character arising as a result of this License or
+ *  out of the use or inability to use the software (including but not limited to damages
+ *  for loss of goodwill, work stoppage, computer failure or malfunction, or any and
+ *  all other commercial damages or losses), even if such Contributor has been advised
+ *  of the possibility of such damages.
+ */
+
+#pragma once
+
+#define IMGUI_DISABLE_DEFAULT_FILE_FUNCTIONS
+#define IMGUI_DEFINE_MATH_OPERATORS
+
+namespace Diligent
+{
+
+#if PLATFORM_WIN32
+class WindowsFile;
+using ImGuiFile = WindowsFile;
+#elif PLATFORM_UNIVERSAL_WINDOWS
+class WindowsStoreFile;
+using ImGuiFile = WindowsStoreFile;
+#elif PLATFORM_ANDROID
+class AndroidFile;
+using ImGuiFile = AndroidFile;
+#else
+class StandardFile;
+using ImGuiFile = StandardFile;
+#endif
+
+} // namespace Diligent
+
+using ImFileHandle = Diligent::ImGuiFile*;
+using ImU64        = unsigned long long;
+
+ImFileHandle ImFileOpen(const char* pFileName, const char* pMode);
+bool         ImFileClose(ImFileHandle pFile);
+ImU64        ImFileGetSize(ImFileHandle pFile);
+ImU64        ImFileRead(void* pData, ImU64 Size, ImU64 Count, ImFileHandle pFile);
+ImU64        ImFileWrite(const void* pData, ImU64 Size, ImU64 Count, ImFileHandle pFile);
diff --git a/Imgui/src/ImGuiDiligentFileIO.cpp b/Imgui/src/ImGuiDiligentFileIO.cpp
new file mode 100644
index 00000000..be67022b
--- /dev/null
+++ b/Imgui/src/ImGuiDiligentFileIO.cpp
@@ -0,0 +1,85 @@
+/*
+ *  Copyright 2026 Diligent Graphics LLC
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  In no event and under no legal theory, whether in tort (including negligence),
+ *  contract, or otherwise, unless required by applicable law (such as deliberate
+ *  and grossly negligent acts) or agreed to in writing, shall any Contributor be
+ *  liable for any damages, including any direct, indirect, special, incidental,
+ *  or consequential damages of any character arising as a result of this License or
+ *  out of the use or inability to use the software (including but not limited to damages
+ *  for loss of goodwill, work stoppage, computer failure or malfunction, or any and
+ *  all other commercial damages or losses), even if such Contributor has been advised
+ *  of the possibility of such damages.
+ */
+
+#include <cstring>
+
+#include "ImGuiDiligentConfig.h"
+#include "imgui.h"
+#include "imgui_internal.h"
+#include "FileSystem.hpp"
+
+using namespace Diligent;
+
+ImFileHandle ImFileOpen(const char* pFileName, const char* pMode)
+{
+    if (!pFileName || !pMode || !pMode[0])
+        return nullptr;
+
+    const bool HasPlus = std::strchr(pMode, '+') != nullptr;
+
+    EFileAccessMode AccessMode = EFileAccessMode::Read;
+
+    switch (pMode[0])
+    {
+        case 'w': AccessMode = HasPlus ? EFileAccessMode::OverwriteUpdate : EFileAccessMode::Overwrite; break;
+        case 'a': AccessMode = HasPlus ? EFileAccessMode::AppendUpdate : EFileAccessMode::Append; break;
+        case 'r': AccessMode = HasPlus ? EFileAccessMode::ReadUpdate : EFileAccessMode::Read; break;
+        default: AccessMode = HasPlus ? EFileAccessMode::ReadUpdate : EFileAccessMode::Read; break;
+    }
+
+    return static_cast<ImFileHandle>(FileSystem::OpenFile({pFileName, AccessMode}));
+}
+
+bool ImFileClose(ImFileHandle pFile)
+{
+    if (!pFile)
+        return false;
+    delete pFile;
+    return true;
+}
+
+ImU64 ImFileGetSize(ImFileHandle pFile)
+{
+    if (!pFile)
+        return static_cast<ImU64>(-1);
+    return static_cast<ImU64>(pFile->GetSize());
+}
+
+ImU64 ImFileRead(void* pData, ImU64 ElemSize, ImU64 ElemCount, ImFileHandle pFile)
+{
+    if (!pFile || ElemSize == 0 || ElemCount == 0)
+        return 0;
+    const size_t TotalSize = static_cast<size_t>(ElemSize * ElemCount);
+    return pFile->Read(pData, TotalSize) ? ElemCount : 0;
+}
+
+ImU64 ImFileWrite(const void* pData, ImU64 ElemSize, ImU64 ElemCount, ImFileHandle pFile)
+{
+    if (!pFile || ElemSize == 0 || ElemCount == 0)
+        return 0;
+    const size_t TotalSize = static_cast<size_t>(ElemSize * ElemCount);
+    return pFile->Write(pData, TotalSize) ? ElemCount : 0;
+}
diff --git a/NativeApp/Apple/Source/Classes/OSX/AppDelegate.m b/NativeApp/Apple/Source/Classes/OSX/AppDelegate.m
index fd52cc43..e6e8bcc6 100644
--- a/NativeApp/Apple/Source/Classes/OSX/AppDelegate.m
+++ b/NativeApp/Apple/Source/Classes/OSX/AppDelegate.m
@@ -17,6 +17,9 @@ @implementation AppDelegate
 - (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
     NSWindow* mainWindow = [[NSApplication sharedApplication]mainWindow];
     [mainWindow setAcceptsMouseMovedEvents:YES];
+
+    // Force dark appearance for the entire application
+    [NSApp setAppearance:[NSAppearance appearanceNamed:NSAppearanceNameDarkAqua]];
 }
 
 - (void)applicationWillTerminate:(NSNotification *)aNotification {
diff --git a/NativeApp/Apple/Source/Classes/OSX/ModeSelectionViewController.mm b/NativeApp/Apple/Source/Classes/OSX/ModeSelectionViewController.mm
index 7121647d..8f1e6cc1 100644
--- a/NativeApp/Apple/Source/Classes/OSX/ModeSelectionViewController.mm
+++ b/NativeApp/Apple/Source/Classes/OSX/ModeSelectionViewController.mm
@@ -33,10 +33,19 @@ @implementation ModeSelectionViewController
 {
 }
 
-- (void) setWindowTitle:(NSString*) title
+- (void) setWindowTitle:(NSString*) title forWindow:(NSWindow*) window
 {
-    NSWindow* mainWindow = [[NSApplication sharedApplication]mainWindow];
-    [mainWindow setTitle:title];
+    [window setTitle:title];
+}
+
+- (void) maximizeWindow:(NSWindow*)window
+{
+    if (window)
+    {
+        // Fill the entire visible screen area (excluding Dock and menu bar)
+        NSRect screenFrame = window.screen.visibleFrame;
+        [window setFrame:screenFrame display:YES animate:YES];
+    }
 }
 
 - (void)viewDidLoad
@@ -97,8 +106,9 @@ - (void) terminateApp:(NSString*) error
 
 - (IBAction)goOpenGL:(id)sender
 {
+    NSWindow* window = self.view.window;
     ViewController* glViewController = [self.storyboard instantiateControllerWithIdentifier:@"GLViewControllerID"];
-    self.view.window.contentViewController = glViewController;
+    window.contentViewController = glViewController;
 
     GLView* glView = (GLView*)[glViewController view];
     NSString* error = [glView getError];
@@ -108,13 +118,15 @@ - (IBAction)goOpenGL:(id)sender
     }
 
     NSString* name =  [glView getAppName];
-    [self setWindowTitle:name];
+    [self setWindowTitle:name forWindow:window];
+    [self maximizeWindow:window];
 }
 
 - (IBAction)goVulkan:(id)sender
 {
+    NSWindow* window = self.view.window;
     ViewController* metalViewController = [self.storyboard instantiateControllerWithIdentifier:@"MoltenVKViewControllerID"];
-    self.view.window.contentViewController = metalViewController;
+    window.contentViewController = metalViewController;
 
     MetalView* mtlView = (MetalView*)[metalViewController view];
     NSString* error = [mtlView getError];
@@ -124,14 +136,16 @@ - (IBAction)goVulkan:(id)sender
     }
 
     NSString* name =  [mtlView getAppName];
-    [self setWindowTitle:name];
+    [self setWindowTitle:name forWindow:window];
+    [self maximizeWindow:window];
 }
 
 - (IBAction)goMetal:(id)sender
 {
+    NSWindow* window = self.view.window;
     ViewController* metalViewController = [self.storyboard instantiateControllerWithIdentifier:@"MetalViewControllerID"];
     MetalView* mtlView = (MetalView*)[metalViewController view];
-    self.view.window.contentViewController = metalViewController;
+    window.contentViewController = metalViewController;
 
     NSString* error = [mtlView getError];
     if(error != nil)
@@ -140,14 +154,16 @@ - (IBAction)goMetal:(id)sender
     }
 
     NSString* name =  [mtlView getAppName];
-    [self setWindowTitle:name];
+    [self setWindowTitle:name forWindow:window];
+    [self maximizeWindow:window];
 }
 
 - (IBAction)goWebGPU:(id)sender
 {
+    NSWindow* window = self.view.window;
     ViewController* webgpuViewController = [self.storyboard instantiateControllerWithIdentifier:@"WebGPUViewControllerID"];
     WebGPUView* webgpuView = (WebGPUView*)[webgpuViewController view];
-    self.view.window.contentViewController = webgpuViewController;
+    window.contentViewController = webgpuViewController;
 
     NSString* error = [webgpuView getError];
     if(error != nil)
@@ -156,7 +172,8 @@ - (IBAction)goWebGPU:(id)sender
     }
 
     NSString* name = [webgpuView getAppName];
-    [self setWindowTitle:name];
+    [self setWindowTitle:name forWindow:window];
+    [self maximizeWindow:window];
 }
 
 @end
diff --git a/NativeApp/Apple/Source/Classes/OSX/WindowController.mm b/NativeApp/Apple/Source/Classes/OSX/WindowController.mm
index cdb15fec..45e4f2b6 100644
--- a/NativeApp/Apple/Source/Classes/OSX/WindowController.mm
+++ b/NativeApp/Apple/Source/Classes/OSX/WindowController.mm
@@ -40,6 +40,25 @@ - (instancetype)initWithWindow:(NSWindow *)window
     return self;
 }
 
+- (void)windowDidLoad
+{
+    [super windowDidLoad];
+
+    NSWindow* window = self.window;
+
+    // Force dark appearance to match the application UI
+    window.appearance = [NSAppearance appearanceNamed:NSAppearanceNameDarkAqua];
+
+    // Make the titlebar transparent so it blends with the window background
+    window.titlebarAppearsTransparent = YES;
+
+    // Set window background color matching ImGuiColors::TitleBg (~0.07, 0.08, 0.11)
+    window.backgroundColor = [NSColor colorWithRed:0.07 green:0.08 blue:0.11 alpha:1.0];
+
+    // Hide the title text (the app name is shown in the content area)
+    window.titleVisibility = NSWindowTitleHidden;
+}
+
 - (void) goFullscreen
 {
     // If app is already fullscreen...