Bring WinUI app to feature/visual parity with WPF, fix drag-and-drop and branding assets

- Restyle Fluent controls (buttons, fields, dialogs, ListView) to match the
  app's navy dark/light palette and consistent corner radii/sizing
- Fix ContentDialog (Settings, exit-confirm, error) styling by binding
  PrimaryButtonStyle/CloseButtonStyle explicitly via new DialogHelper,
  since ContentDialog ignores implicit Button styles and forces accent
  color onto whichever button is DefaultButton
- Remove MicaBackdrop and theme the title bar directly so it no longer
  shows a gray tint mismatched with the app's navy background
- Replace placeholder Assets/*.png (unused VS template art) with the real
  AmiReel logo at all required tile/splash/store sizes
- Set explicit default window size (1280x860, matching the old WPF app)
  with DPI-aware centering and a minimum size, instead of sizing to content
- Fix drag-and-drop silently failing: InputList_Drop needs a
  DragOperationDeferral before the first await or the DataView is torn
  down before GetStorageItemsAsync completes
- Add Preview player path setting (was present in WPF, missing in WinUI)
  and error handling for preview playback
- Accept all ffmpeg-readable video formats (mp4, mov, mkv, webm, ...) for
  file picker and drag-and-drop, not just .avi
- Add exit-confirmation dialog to WinUI, mirroring the WPF app

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

AmiReel.WinUI/App.xaml

@@ -23,6 +23,54 @@
                     <SolidColorBrush x:Key="ButtonBrush" Color="#243554"/>
                     <SolidColorBrush x:Key="ButtonHoverBrush" Color="#2E446C"/>
                     <SolidColorBrush x:Key="PrimaryTextBrush" Color="#07111D"/>
+
+                    <!-- Fluent control theme-brush overrides so built-in controls match the palette -->
+                    <SolidColorBrush x:Key="TextControlBackground" Color="#1D2940"/>
+                    <SolidColorBrush x:Key="TextControlBackgroundPointerOver" Color="#233252"/>
+                    <SolidColorBrush x:Key="TextControlBackgroundFocused" Color="#1D2940"/>
+                    <SolidColorBrush x:Key="TextControlBorderBrush" Color="#2B3A58"/>
+                    <SolidColorBrush x:Key="TextControlBorderBrushPointerOver" Color="#4AB8FF"/>
+                    <SolidColorBrush x:Key="TextControlBorderBrushFocused" Color="#4AB8FF"/>
+                    <SolidColorBrush x:Key="TextControlForeground" Color="#F5F7FB"/>
+                    <SolidColorBrush x:Key="TextControlForegroundFocused" Color="#F5F7FB"/>
+                    <SolidColorBrush x:Key="TextControlHeaderForeground" Color="#9FB1CC"/>
+                    <SolidColorBrush x:Key="TextControlPlaceholderForeground" Color="#7488A6"/>
+
+                    <SolidColorBrush x:Key="ComboBoxBackground" Color="#1D2940"/>
+                    <SolidColorBrush x:Key="ComboBoxBackgroundPointerOver" Color="#233252"/>
+                    <SolidColorBrush x:Key="ComboBoxBorderBrush" Color="#2B3A58"/>
+                    <SolidColorBrush x:Key="ComboBoxForeground" Color="#F5F7FB"/>
+                    <SolidColorBrush x:Key="ComboBoxHeaderForeground" Color="#9FB1CC"/>
+                    <SolidColorBrush x:Key="ComboBoxItemBackgroundSelected" Color="#13324F"/>
+                    <SolidColorBrush x:Key="ComboBoxDropDownBackground" Color="#10192B"/>
+
+                    <SolidColorBrush x:Key="ButtonBackground" Color="#243554"/>
+                    <SolidColorBrush x:Key="ButtonBackgroundPointerOver" Color="#2E446C"/>
+                    <SolidColorBrush x:Key="ButtonBackgroundPressed" Color="#1B2A44"/>
+                    <SolidColorBrush x:Key="ButtonForeground" Color="#F5F7FB"/>
+                    <SolidColorBrush x:Key="ButtonForegroundPointerOver" Color="#F5F7FB"/>
+                    <SolidColorBrush x:Key="ButtonBorderBrush" Color="#2B3A58"/>
+
+                    <SolidColorBrush x:Key="ContentDialogBackground" Color="#162033"/>
+                    <SolidColorBrush x:Key="ContentDialogForeground" Color="#F5F7FB"/>
+                    <SolidColorBrush x:Key="ContentDialogBorderBrush" Color="#35507D"/>
+
+                    <SolidColorBrush x:Key="ListViewItemBackgroundSelected" Color="#13324F"/>
+                    <SolidColorBrush x:Key="ListViewItemBackgroundPointerOver" Color="#1A2740"/>
+                    <SolidColorBrush x:Key="ListViewItemForeground" Color="#F5F7FB"/>
+
+                    <SolidColorBrush x:Key="CheckBoxCheckBackgroundFillUnchecked" Color="#1D2940"/>
+                    <SolidColorBrush x:Key="CheckBoxCheckBackgroundStrokeUnchecked" Color="#2B3A58"/>
+                    <SolidColorBrush x:Key="CheckBoxCheckBackgroundFillChecked" Color="#4AB8FF"/>
+                    <SolidColorBrush x:Key="CheckBoxCheckBackgroundStrokeChecked" Color="#4AB8FF"/>
+                    <SolidColorBrush x:Key="CheckBoxCheckGlyphForegroundChecked" Color="#07111D"/>
+                    <SolidColorBrush x:Key="CheckBoxForegroundUnchecked" Color="#F5F7FB"/>
+                    <SolidColorBrush x:Key="CheckBoxForegroundChecked" Color="#F5F7FB"/>
+
+                    <SolidColorBrush x:Key="ProgressBarForeground" Color="#4AB8FF"/>
+                    <SolidColorBrush x:Key="ProgressBarBackground" Color="#1D2940"/>
+
+                    <SolidColorBrush x:Key="HeroBorderBrush" Color="#35507D"/>
                 </ResourceDictionary>
                 <ResourceDictionary x:Key="Light">
                     <SolidColorBrush x:Key="PageBrush" Color="#F4F7FB"/>
@@ -37,11 +85,65 @@
                     <SolidColorBrush x:Key="ButtonBrush" Color="#E5EDF7"/>
                     <SolidColorBrush x:Key="ButtonHoverBrush" Color="#D7E4F4"/>
                     <SolidColorBrush x:Key="PrimaryTextBrush" Color="#FFFFFF"/>
+
+                    <SolidColorBrush x:Key="TextControlBackground" Color="#F7FAFD"/>
+                    <SolidColorBrush x:Key="TextControlBackgroundPointerOver" Color="#EEF4FB"/>
+                    <SolidColorBrush x:Key="TextControlBackgroundFocused" Color="#FFFFFF"/>
+                    <SolidColorBrush x:Key="TextControlBorderBrush" Color="#C7D3E3"/>
+                    <SolidColorBrush x:Key="TextControlBorderBrushPointerOver" Color="#0E9AEF"/>
+                    <SolidColorBrush x:Key="TextControlBorderBrushFocused" Color="#0E9AEF"/>
+                    <SolidColorBrush x:Key="TextControlForeground" Color="#122033"/>
+                    <SolidColorBrush x:Key="TextControlForegroundFocused" Color="#122033"/>
+                    <SolidColorBrush x:Key="TextControlHeaderForeground" Color="#5F7390"/>
+                    <SolidColorBrush x:Key="TextControlPlaceholderForeground" Color="#8194AC"/>
+
+                    <SolidColorBrush x:Key="ComboBoxBackground" Color="#F7FAFD"/>
+                    <SolidColorBrush x:Key="ComboBoxBackgroundPointerOver" Color="#EEF4FB"/>
+                    <SolidColorBrush x:Key="ComboBoxBorderBrush" Color="#C7D3E3"/>
+                    <SolidColorBrush x:Key="ComboBoxForeground" Color="#122033"/>
+                    <SolidColorBrush x:Key="ComboBoxHeaderForeground" Color="#5F7390"/>
+                    <SolidColorBrush x:Key="ComboBoxItemBackgroundSelected" Color="#D6EEFF"/>
+                    <SolidColorBrush x:Key="ComboBoxDropDownBackground" Color="#FFFFFF"/>
+
+                    <SolidColorBrush x:Key="ButtonBackground" Color="#E5EDF7"/>
+                    <SolidColorBrush x:Key="ButtonBackgroundPointerOver" Color="#D7E4F4"/>
+                    <SolidColorBrush x:Key="ButtonBackgroundPressed" Color="#C7D9EE"/>
+                    <SolidColorBrush x:Key="ButtonForeground" Color="#122033"/>
+                    <SolidColorBrush x:Key="ButtonForegroundPointerOver" Color="#122033"/>
+                    <SolidColorBrush x:Key="ButtonBorderBrush" Color="#C7D3E3"/>
+
+                    <SolidColorBrush x:Key="ContentDialogBackground" Color="#FFFFFF"/>
+                    <SolidColorBrush x:Key="ContentDialogForeground" Color="#122033"/>
+                    <SolidColorBrush x:Key="ContentDialogBorderBrush" Color="#C7D3E3"/>
+
+                    <SolidColorBrush x:Key="ListViewItemBackgroundSelected" Color="#D6EEFF"/>
+                    <SolidColorBrush x:Key="ListViewItemBackgroundPointerOver" Color="#EEF4FB"/>
+                    <SolidColorBrush x:Key="ListViewItemForeground" Color="#122033"/>
+
+                    <SolidColorBrush x:Key="CheckBoxCheckBackgroundFillUnchecked" Color="#F7FAFD"/>
+                    <SolidColorBrush x:Key="CheckBoxCheckBackgroundStrokeUnchecked" Color="#C7D3E3"/>
+                    <SolidColorBrush x:Key="CheckBoxCheckBackgroundFillChecked" Color="#0E9AEF"/>
+                    <SolidColorBrush x:Key="CheckBoxCheckBackgroundStrokeChecked" Color="#0E9AEF"/>
+                    <SolidColorBrush x:Key="CheckBoxCheckGlyphForegroundChecked" Color="#FFFFFF"/>
+                    <SolidColorBrush x:Key="CheckBoxForegroundUnchecked" Color="#122033"/>
+                    <SolidColorBrush x:Key="CheckBoxForegroundChecked" Color="#122033"/>
+
+                    <SolidColorBrush x:Key="ProgressBarForeground" Color="#0E9AEF"/>
+                    <SolidColorBrush x:Key="ProgressBarBackground" Color="#F7FAFD"/>
+
+                    <SolidColorBrush x:Key="HeroBorderBrush" Color="#A9C4E4"/>
                 </ResourceDictionary>
             </ResourceDictionary.ThemeDictionaries>
 
+            <!-- Global corner rounding so built-in Fluent controls match the WPF app's rounded look -->
+            <CornerRadius x:Key="ControlCornerRadius">10</CornerRadius>
+            <CornerRadius x:Key="OverlayCornerRadius">18</CornerRadius>
+
+            <x:Double x:Key="ContentDialogMaxWidth">460</x:Double>
+
             <Style TargetType="Page">
                 <Setter Property="Background" Value="{ThemeResource PageBrush}" />
+                <Setter Property="FontFamily" Value="Bahnschrift" />
             </Style>
 
             <Style x:Key="CardBorderStyle" TargetType="Border">
@@ -53,51 +155,114 @@
 
             <Style x:Key="SectionTitleStyle" TargetType="TextBlock">
                 <Setter Property="Foreground" Value="{ThemeResource TextBrush}" />
-                <Setter Property="FontSize" Value="24" />
+                <Setter Property="FontSize" Value="15" />
                 <Setter Property="FontWeight" Value="SemiBold" />
             </Style>
 
             <Style x:Key="MutedTextStyle" TargetType="TextBlock">
                 <Setter Property="Foreground" Value="{ThemeResource MutedBrush}" />
+                <Setter Property="FontSize" Value="13" />
+            </Style>
+
+            <Style x:Key="FieldLabelStyle" TargetType="TextBlock">
+                <Setter Property="Foreground" Value="{ThemeResource MutedBrush}" />
+                <Setter Property="FontSize" Value="12" />
+                <Setter Property="Margin" Value="0,0,0,4" />
+            </Style>
+
+            <Style TargetType="TextBlock">
+                <Setter Property="Foreground" Value="{ThemeResource TextBrush}" />
+                <Setter Property="FontSize" Value="13" />
             </Style>
 
             <Style TargetType="Button">
-                <Setter Property="Background" Value="{ThemeResource ButtonBrush}" />
-                <Setter Property="Foreground" Value="{ThemeResource TextBrush}" />
-                <Setter Property="BorderBrush" Value="{ThemeResource BorderBrush}" />
+                <Setter Property="Padding" Value="16,9" />
+                <Setter Property="FontSize" Value="13" />
+                <Setter Property="CornerRadius" Value="10" />
             </Style>
 
             <Style x:Key="PrimaryButtonStyle" TargetType="Button">
                 <Setter Property="Background" Value="{ThemeResource AccentBrush}" />
                 <Setter Property="Foreground" Value="{ThemeResource PrimaryTextBrush}" />
                 <Setter Property="BorderBrush" Value="{ThemeResource AccentBrush}" />
+                <Setter Property="FontWeight" Value="SemiBold" />
+                <Setter Property="Padding" Value="22,10" />
+                <Setter Property="CornerRadius" Value="10" />
+            </Style>
+
+            <Style x:Key="IconButtonStyle" TargetType="Button">
+                <Setter Property="Width" Value="40" />
+                <Setter Property="Height" Value="40" />
+                <Setter Property="Padding" Value="0" />
+                <Setter Property="FontSize" Value="16" />
+                <Setter Property="CornerRadius" Value="10" />
+                <Setter Property="HorizontalContentAlignment" Value="Center" />
+                <Setter Property="VerticalContentAlignment" Value="Center" />
+            </Style>
+
+            <!-- Explicit styles bound to ContentDialog.PrimaryButtonStyle / CloseButtonStyle so its
+                 built-in buttons match the app's own Button look instead of the default Fluent
+                 accent-pill / plain styles. -->
+            <Style x:Key="DialogPrimaryButtonStyle" TargetType="Button">
+                <Setter Property="Background" Value="{ThemeResource AccentBrush}" />
+                <Setter Property="Foreground" Value="{ThemeResource PrimaryTextBrush}" />
+                <Setter Property="BorderBrush" Value="{ThemeResource AccentBrush}" />
+                <Setter Property="BorderThickness" Value="1" />
+                <Setter Property="FontWeight" Value="SemiBold" />
+                <Setter Property="FontSize" Value="13" />
+                <Setter Property="Padding" Value="22,10" />
+                <Setter Property="CornerRadius" Value="10" />
+                <Setter Property="MinHeight" Value="40" />
+                <Setter Property="MinWidth" Value="110" />
+            </Style>
+
+            <Style x:Key="DialogCloseButtonStyle" TargetType="Button">
+                <Setter Property="Background" Value="{ThemeResource ButtonBrush}" />
+                <Setter Property="Foreground" Value="{ThemeResource TextBrush}" />
+                <Setter Property="BorderBrush" Value="{ThemeResource BorderBrush}" />
+                <Setter Property="BorderThickness" Value="1" />
+                <Setter Property="FontSize" Value="13" />
+                <Setter Property="Padding" Value="16,9" />
+                <Setter Property="CornerRadius" Value="10" />
+                <Setter Property="MinHeight" Value="40" />
+                <Setter Property="MinWidth" Value="110" />
             </Style>
 
             <Style TargetType="TextBox">
-                <Setter Property="Background" Value="{ThemeResource FieldBrush}" />
-                <Setter Property="Foreground" Value="{ThemeResource TextBrush}" />
-                <Setter Property="BorderBrush" Value="{ThemeResource BorderBrush}" />
+                <Setter Property="FontSize" Value="13" />
+                <Setter Property="MinHeight" Value="38" />
             </Style>
 
             <Style TargetType="ComboBox">
-                <Setter Property="Background" Value="{ThemeResource FieldBrush}" />
-                <Setter Property="Foreground" Value="{ThemeResource TextBrush}" />
-                <Setter Property="BorderBrush" Value="{ThemeResource BorderBrush}" />
+                <Setter Property="FontSize" Value="13" />
+                <Setter Property="MinHeight" Value="38" />
+            </Style>
+
+            <Style TargetType="CheckBox">
+                <Setter Property="FontSize" Value="13" />
             </Style>
 
             <Style TargetType="ProgressBar">
-                <Setter Property="Foreground" Value="{ThemeResource AccentBrush}" />
-                <Setter Property="Background" Value="{ThemeResource FieldBrush}" />
+                <Setter Property="MinHeight" Value="8" />
             </Style>
 
             <Style TargetType="ListView">
                 <Setter Property="Background" Value="{ThemeResource FieldBrush}" />
                 <Setter Property="BorderBrush" Value="{ThemeResource BorderBrush}" />
-                <Setter Property="Foreground" Value="{ThemeResource TextBrush}" />
+                <Setter Property="BorderThickness" Value="1" />
+                <Setter Property="CornerRadius" Value="10" />
+                <Setter Property="FontSize" Value="13" />
+                <Setter Property="Padding" Value="4" />
             </Style>
 
-            <Style TargetType="TextBlock">
-                <Setter Property="Foreground" Value="{ThemeResource TextBrush}" />
+            <Style TargetType="ListViewItem">
+                <Setter Property="MinHeight" Value="32" />
+                <Setter Property="Padding" Value="8,6" />
+                <Setter Property="CornerRadius" Value="6" />
+            </Style>
+
+            <Style TargetType="ContentDialog">
+                <Setter Property="CornerRadius" Value="18" />
             </Style>
         </ResourceDictionary>
     </Application.Resources>

AmiReel.WinUI/App.xaml.cs

@@ -24,6 +24,7 @@ public partial class App : Application
 {
     private Window? _window;
     public static IntPtr MainWindowHandle { get; private set; }
+    public static MainWindow? MainWindowInstance { get; set; }
     
     /// <summary>
     /// Initializes the singleton application object.  This is the first line of authored code

AmiReel.WinUI/DialogHelper.cs

@@ -0,0 +1,33 @@
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Media;
+
+namespace AmiReel_WinUI;
+
+/// <summary>
+/// Builds ContentDialogs styled to match the app's own palette and button shapes,
+/// since ContentDialog's default Fluent look (accent-pill primary button, plain
+/// square close button, ungrouped theme resources) does not follow our custom brushes.
+/// </summary>
+internal static class DialogHelper
+{
+    public static ContentDialog CreateStyled(XamlRoot xamlRoot, ElementTheme theme)
+    {
+        string themeKey = theme == ElementTheme.Dark ? "Dark" : "Light";
+        ResourceDictionary themeDictionary = (ResourceDictionary)Application.Current.Resources.ThemeDictionaries[themeKey];
+
+        return new ContentDialog
+        {
+            XamlRoot = xamlRoot,
+            RequestedTheme = theme,
+            Background = (Brush)themeDictionary["PanelBrush"],
+            Foreground = (Brush)themeDictionary["TextBrush"],
+            BorderBrush = (Brush)themeDictionary["HeroBorderBrush"],
+            BorderThickness = new Thickness(1.5),
+            CornerRadius = new CornerRadius(18),
+            PrimaryButtonStyle = (Style)Application.Current.Resources["DialogPrimaryButtonStyle"],
+            SecondaryButtonStyle = (Style)Application.Current.Resources["DialogCloseButtonStyle"],
+            CloseButtonStyle = (Style)Application.Current.Resources["DialogCloseButtonStyle"]
+        };
+    }
+}

AmiReel.WinUI/MainPage.xaml

@@ -25,16 +25,17 @@
                 <StackPanel Spacing="12">
                     <TextBlock Text="Source recordings" Style="{StaticResource SectionTitleStyle}" />
                     <StackPanel Orientation="Horizontal" Spacing="10">
-                        <Button Content="Add AVI files..." Click="AddInputs_Click" />
+                        <Button Content="Add video files..." Click="AddInputs_Click" />
                         <Button Content="Clear" Click="ClearInputs_Click" />
                     </StackPanel>
                     <ListView x:Name="InputList"
-                              Height="120"
+                              Height="130"
                               SelectionMode="Single"
                               SelectionChanged="InputList_SelectionChanged"
                               AllowDrop="True"
                               DragOver="InputList_DragOver"
-                              Drop="InputList_Drop" />
+                              Drop="InputList_Drop"
+                              ToolTipService.ToolTip="Drag and drop video files here to add them" />
                     <Button x:Name="PreviewSourceButton"
                             Content="Preview selected"
                             Click="PreviewSource_Click"
@@ -59,13 +60,13 @@
                             <RowDefinition Height="Auto" />
                         </Grid.RowDefinitions>
 
-                        <TextBox x:Name="EndCardBox" Grid.Row="0" MinHeight="48" />
+                        <TextBox x:Name="EndCardBox" Grid.Row="0" MinHeight="40" />
                         <Button Grid.Row="0" Grid.Column="1" Content="Browse..." Click="BrowseEndCard_Click" VerticalAlignment="Stretch" MinWidth="120" />
 
-                        <TextBox x:Name="OutputFolderBox" Grid.Row="1" MinHeight="48" />
+                        <TextBox x:Name="OutputFolderBox" Grid.Row="1" MinHeight="40" />
                         <Button Grid.Row="1" Grid.Column="1" Content="Browse..." Click="BrowseOutput_Click" VerticalAlignment="Stretch" MinWidth="120" />
 
-                        <TextBox x:Name="OutputNameBox" Grid.Row="2" Grid.ColumnSpan="2" MinHeight="48" />
+                        <TextBox x:Name="OutputNameBox" Grid.Row="2" Grid.ColumnSpan="2" MinHeight="40" />
                     </Grid>
                 </StackPanel>
             </Border>
@@ -75,10 +76,10 @@
             <StackPanel Spacing="12">
                 <TextBlock Text="Render progress" Style="{StaticResource SectionTitleStyle}" />
                 <StackPanel Orientation="Horizontal" Spacing="6">
-                    <TextBlock x:Name="StageText" Text="Ready" FontSize="18" FontWeight="SemiBold" />
-                    <TextBlock x:Name="PercentText" Text="0%" FontSize="18" FontWeight="SemiBold" Foreground="{ThemeResource AccentBrush}" />
+                    <TextBlock x:Name="StageText" Text="Ready" FontSize="15" FontWeight="SemiBold" />
+                    <TextBlock x:Name="PercentText" Text="0%" FontSize="15" FontWeight="SemiBold" Foreground="{ThemeResource AccentBrush}" />
                 </StackPanel>
-                <ProgressBar x:Name="RenderProgressBar" Minimum="0" Maximum="100" Height="10" />
+                <ProgressBar x:Name="RenderProgressBar" Minimum="0" Maximum="100" Height="8" />
                 <TextBlock x:Name="StatusText" Text="Select the recordings and start the render. The end card is optional." TextWrapping="WrapWholeWords" Style="{StaticResource MutedTextStyle}" />
             </StackPanel>
         </Border>
@@ -111,7 +112,8 @@
             </StackPanel>
 
             <StackPanel Grid.Column="1" Orientation="Horizontal" Spacing="10">
-                <Button x:Name="OpenSettingsButton" Content="Settings" Click="OpenSettings_Click" />
+                <Button x:Name="OpenSettingsButton" Content="&#xE713;" FontFamily="Segoe Fluent Icons, Segoe MDL2 Assets"
+                        Click="OpenSettings_Click" Style="{StaticResource IconButtonStyle}" ToolTipService.ToolTip="Settings" />
                 <Button x:Name="CancelButton" Content="Cancel" Click="Cancel_Click" IsEnabled="False" />
                 <Button x:Name="RenderButton" Content="Start render" Click="Render_Click" Style="{StaticResource PrimaryButtonStyle}" />
             </StackPanel>
@@ -121,7 +123,14 @@
                        Title="Settings"
                        PrimaryButtonText="Done"
                        CloseButtonText="Close"
-                       DefaultButton="Primary">
+                       DefaultButton="Primary"
+                       Background="{ThemeResource PanelBrush}"
+                       Foreground="{ThemeResource TextBrush}"
+                       BorderBrush="{ThemeResource HeroBorderBrush}"
+                       BorderThickness="1.5"
+                       CornerRadius="18"
+                       PrimaryButtonStyle="{StaticResource DialogPrimaryButtonStyle}"
+                       CloseButtonStyle="{StaticResource DialogCloseButtonStyle}">
             <ScrollViewer MaxHeight="560" VerticalScrollBarVisibility="Auto">
                 <StackPanel Spacing="16">
                     <Border Padding="14" Background="{ThemeResource PanelAltBrush}" BorderBrush="{ThemeResource BorderBrush}" BorderThickness="1" CornerRadius="12">
@@ -190,11 +199,14 @@
                                 <Grid.RowDefinitions>
                                     <RowDefinition Height="Auto" />
                                     <RowDefinition Height="Auto" />
+                                    <RowDefinition Height="Auto" />
                                 </Grid.RowDefinitions>
                                 <TextBox x:Name="FfmpegPathBox" Grid.Row="0" Header="ffmpeg.exe path" />
                                 <Button Grid.Row="0" Grid.Column="1" Content="Browse..." Click="BrowseFfmpeg_Click" VerticalAlignment="Bottom" />
                                 <TextBox x:Name="FfprobePathBox" Grid.Row="1" Header="ffprobe.exe path" />
                                 <Button Grid.Row="1" Grid.Column="1" Content="Browse..." Click="BrowseFfprobe_Click" VerticalAlignment="Bottom" />
+                                <TextBox x:Name="PreviewPlayerPathBox" Grid.Row="2" Header="Preview player path (optional, e.g. mpv.exe)" />
+                                <Button Grid.Row="2" Grid.Column="1" Content="Browse..." Click="BrowsePreviewPlayer_Click" VerticalAlignment="Bottom" />
                             </Grid>
                         </StackPanel>
                     </Border>

AmiReel.WinUI/MainPage.xaml.cs

@@ -33,6 +33,7 @@ public sealed partial class MainPage : Page
         EndCardBox.Text = _loadedSettings.EndCardPath;
         FfmpegPathBox.Text = _loadedSettings.FfmpegPath;
         FfprobePathBox.Text = _loadedSettings.FfprobePath;
+        PreviewPlayerPathBox.Text = _loadedSettings.PreviewPlayerPath;
         OutputNameBox.Text = "amigadb_intro";
         TrimBox.Text = _loadedSettings.TrimStart;
         FadeBox.Text = _loadedSettings.FadeSeconds;
@@ -47,7 +48,8 @@ public sealed partial class MainPage : Page
     private async void AddInputs_Click(object sender, RoutedEventArgs e)
     {
         FileOpenPicker picker = CreateFileOpenPicker();
-        picker.FileTypeFilter.Add(".avi");
+        foreach (string extension in SupportedVideoFormats.Extensions)
+            picker.FileTypeFilter.Add(extension);
         picker.SuggestedStartLocation = PickerLocationId.VideosLibrary;
         var files = await picker.PickMultipleFilesAsync();
         if (files is null) return;
@@ -69,12 +71,20 @@ public sealed partial class MainPage : Page
     {
         if (!e.DataView.Contains(StandardDataFormats.StorageItems)) return;
 
-        IReadOnlyList<IStorageItem> items = await e.DataView.GetStorageItemsAsync();
-        foreach (string path in items.OfType<StorageFile>()
-                     .Select(file => file.Path)
-                     .Where(path => string.Equals(Path.GetExtension(path), ".avi", StringComparison.OrdinalIgnoreCase))
-                     .OrderBy(NaturalKey))
-            if (!_inputs.Contains(path, StringComparer.OrdinalIgnoreCase)) _inputs.Add(path);
+        DragOperationDeferral deferral = e.GetDeferral();
+        try
+        {
+            IReadOnlyList<IStorageItem> items = await e.DataView.GetStorageItemsAsync();
+            foreach (string path in items.OfType<StorageFile>()
+                         .Select(file => file.Path)
+                         .Where(SupportedVideoFormats.IsSupported)
+                         .OrderBy(NaturalKey))
+                if (!_inputs.Contains(path, StringComparer.OrdinalIgnoreCase)) _inputs.Add(path);
+        }
+        finally
+        {
+            deferral.Complete();
+        }
     }
 
     private async void BrowseEndCard_Click(object sender, RoutedEventArgs e)
@@ -116,6 +126,15 @@ public sealed partial class MainPage : Page
             FfprobePathBox.Text = file.Path;
     }
 
+    private async void BrowsePreviewPlayer_Click(object sender, RoutedEventArgs e)
+    {
+        FileOpenPicker picker = CreateFileOpenPicker();
+        picker.FileTypeFilter.Add(".exe");
+        var file = await picker.PickSingleFileAsync();
+        if (file is not null)
+            PreviewPlayerPathBox.Text = file.Path;
+    }
+
     private async void OpenSettings_Click(object sender, RoutedEventArgs e)
     {
         SettingsDialog.XamlRoot = XamlRoot;
@@ -171,16 +190,16 @@ public sealed partial class MainPage : Page
             Process.Start(new ProcessStartInfo("explorer.exe", OutputFolderBox.Text) { UseShellExecute = true });
     }
 
-    private void PreviewSource_Click(object sender, RoutedEventArgs e)
+    private async void PreviewSource_Click(object sender, RoutedEventArgs e)
     {
         if (InputList.SelectedItem is string path)
-            OpenPreview(path);
+            await OpenPreviewAsync(path);
     }
 
-    private void PreviewRendered_Click(object sender, RoutedEventArgs e)
+    private async void PreviewRendered_Click(object sender, RoutedEventArgs e)
     {
         if (!string.IsNullOrWhiteSpace(_lastRenderedFile) && File.Exists(_lastRenderedFile))
-            OpenPreview(_lastRenderedFile);
+            await OpenPreviewAsync(_lastRenderedFile);
     }
 
     private void ThemeBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
@@ -241,12 +260,39 @@ public sealed partial class MainPage : Page
         StatusText.Text = value.Message;
     }
 
-    private void OpenPreview(string mediaPath)
+    private async Task OpenPreviewAsync(string mediaPath)
     {
         if (!File.Exists(mediaPath))
+        {
+            await ShowMessageAsync("Preview unavailable", "The selected media file was not found.");
             return;
+        }
 
-        Process.Start(new ProcessStartInfo(mediaPath) { UseShellExecute = true });
+        string playerPath = PreviewPlayerPathBox.Text.Trim();
+
+        try
+        {
+            if (!string.IsNullOrWhiteSpace(playerPath))
+            {
+                if (!File.Exists(playerPath))
+                    throw new FileNotFoundException("Configured preview player was not found.", playerPath);
+
+                ProcessStartInfo customPlayer = new()
+                {
+                    FileName = playerPath,
+                    UseShellExecute = false
+                };
+                customPlayer.ArgumentList.Add(mediaPath);
+                Process.Start(customPlayer);
+                return;
+            }
+
+            Process.Start(new ProcessStartInfo(mediaPath) { UseShellExecute = true });
+        }
+        catch (Exception exception)
+        {
+            await ShowMessageAsync("Preview failed", exception.Message);
+        }
     }
 
     private void AppendLog(string line)
@@ -285,7 +331,7 @@ public sealed partial class MainPage : Page
             EndCardBox.Text.Trim(),
             FfmpegPathBox.Text.Trim(),
             FfprobePathBox.Text.Trim(),
-            _loadedSettings.PreviewPlayerPath,
+            PreviewPlayerPathBox.Text.Trim(),
             SelectedTheme(),
             SelectedEncoder(),
             TrimBox.Text.Trim(),
@@ -334,9 +380,8 @@ public sealed partial class MainPage : Page
 
     private void ApplyTheme(string theme)
     {
-        RequestedTheme = string.Equals(theme, "Light", StringComparison.OrdinalIgnoreCase)
-            ? ElementTheme.Light
-            : ElementTheme.Dark;
+        bool isDark = !string.Equals(theme, "Light", StringComparison.OrdinalIgnoreCase);
+        App.MainWindowInstance?.ApplyTheme(isDark);
     }
 
     private FileOpenPicker CreateFileOpenPicker()
@@ -365,13 +410,10 @@ public sealed partial class MainPage : Page
 
     private async Task ShowMessageAsync(string title, string message)
     {
-        ContentDialog dialog = new()
-        {
-            Title = title,
-            Content = message,
-            CloseButtonText = "OK",
-            XamlRoot = XamlRoot
-        };
+        ContentDialog dialog = DialogHelper.CreateStyled(XamlRoot, ActualTheme);
+        dialog.Title = title;
+        dialog.Content = message;
+        dialog.CloseButtonText = "OK";
         await dialog.ShowAsync();
     }
 }

AmiReel.WinUI/MainWindow.xaml

@@ -8,24 +8,22 @@
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     Title="AmiReel"
     mc:Ignorable="d">
-    <Window.SystemBackdrop>
-        <MicaBackdrop />
-    </Window.SystemBackdrop>
-
-    <Grid>
+    <Grid Background="{ThemeResource PageBrush}">
         <Grid.RowDefinitions>
             <RowDefinition Height="Auto" />
             <RowDefinition Height="*" />
         </Grid.RowDefinitions>
 
-        <Grid x:Name="AppTitleBar" Height="44" Background="Transparent">
+        <Grid x:Name="AppTitleBar" Grid.Row="0" Height="44" Background="{ThemeResource PanelBrush}">
             <StackPanel Orientation="Horizontal" Spacing="10" VerticalAlignment="Center" Margin="14,0,0,0">
                 <Image Source="ms-appx:///Assets/Square44x44Logo.scale-200.png"
                        Width="20"
                        Height="20"
                        Stretch="Uniform" />
                 <TextBlock Text="AmiReel"
-                           FontSize="16"
+                           FontFamily="Bahnschrift"
+                           FontSize="14"
+                           FontWeight="SemiBold"
                            VerticalAlignment="Center" />
             </StackPanel>
         </Grid>

AmiReel.WinUI/MainWindow.xaml.cs

@@ -1,8 +1,13 @@
+using Microsoft.UI;
 using Microsoft.UI.Windowing;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
 using System;
 using System.IO;
+using System.Runtime.InteropServices;
+using Windows.Graphics;
+using Windows.UI;
+using WinRT.Interop;
 
 // To learn more about WinUI, the WinUI project structure,
 // and more about our project templates, see: http://aka.ms/winui-project-info.
@@ -21,6 +26,7 @@ public sealed partial class MainWindow : Window
     public MainWindow()
     {
         InitializeComponent();
+        App.MainWindowInstance = this;
 
         ExtendsContentIntoTitleBar = true;
         SetTitleBar(AppTitleBar);
@@ -29,26 +35,77 @@ public sealed partial class MainWindow : Window
         if (!string.IsNullOrWhiteSpace(executablePath) && File.Exists(executablePath))
             AppWindow.SetIcon(executablePath);
 
+        SetDefaultSizeAndPosition();
+
         // Navigate the root frame to the main page on startup.
         RootFrame.Navigate(typeof(MainPage));
 
         AppWindow.Closing += AppWindow_Closing;
     }
 
+    private void SetDefaultSizeAndPosition()
+    {
+        const int DefaultWidth = 1280;
+        const int DefaultHeight = 860;
+        const int MinWidth = 1100;
+        const int MinHeight = 780;
+
+        IntPtr hwnd = WindowNative.GetWindowHandle(this);
+        double scale = GetDpiForWindow(hwnd) / 96.0;
+        int width = (int)(DefaultWidth * scale);
+        int height = (int)(DefaultHeight * scale);
+
+        AppWindow.Resize(new SizeInt32(width, height));
+
+        if (AppWindow.Presenter is OverlappedPresenter presenter)
+        {
+            presenter.PreferredMinimumWidth = (int)(MinWidth * scale);
+            presenter.PreferredMinimumHeight = (int)(MinHeight * scale);
+        }
+
+        DisplayArea? displayArea = DisplayArea.GetFromWindowId(Win32Interop.GetWindowIdFromWindow(hwnd), DisplayAreaFallback.Primary);
+        if (displayArea is not null)
+        {
+            int centerX = displayArea.WorkArea.X + (displayArea.WorkArea.Width - width) / 2;
+            int centerY = displayArea.WorkArea.Y + (displayArea.WorkArea.Height - height) / 2;
+            AppWindow.Move(new PointInt32(centerX, centerY));
+        }
+    }
+
+    [DllImport("user32.dll")]
+    private static extern int GetDpiForWindow(IntPtr hwnd);
+
+    public void ApplyTheme(bool isDark)
+    {
+        if (Content is FrameworkElement root)
+            root.RequestedTheme = isDark ? ElementTheme.Dark : ElementTheme.Light;
+
+        AppWindowTitleBar titleBar = AppWindow.TitleBar;
+        Color foreground = isDark ? Color.FromArgb(255, 0xF5, 0xF7, 0xFB) : Color.FromArgb(255, 0x12, 0x20, 0x33);
+        Color hoverBackground = isDark ? Color.FromArgb(255, 0x2E, 0x44, 0x6C) : Color.FromArgb(255, 0xD7, 0xE4, 0xF4);
+
+        titleBar.ButtonBackgroundColor = Colors.Transparent;
+        titleBar.ButtonInactiveBackgroundColor = Colors.Transparent;
+        titleBar.ButtonForegroundColor = foreground;
+        titleBar.ButtonInactiveForegroundColor = foreground;
+        titleBar.ButtonHoverBackgroundColor = hoverBackground;
+        titleBar.ButtonHoverForegroundColor = foreground;
+        titleBar.ButtonPressedBackgroundColor = hoverBackground;
+        titleBar.ButtonPressedForegroundColor = foreground;
+    }
+
     private async void AppWindow_Closing(AppWindow sender, AppWindowClosingEventArgs args)
     {
         if (_exitConfirmed) return;
         args.Cancel = true;
 
-        ContentDialog dialog = new()
-        {
-            Title = "Exit AmiReel?",
-            Content = "Are you sure you want to close the application?",
-            PrimaryButtonText = "Exit",
-            CloseButtonText = "Cancel",
-            DefaultButton = ContentDialogButton.Close,
-            XamlRoot = RootFrame.XamlRoot
-        };
+        FrameworkElement root = (FrameworkElement)Content;
+        ContentDialog dialog = DialogHelper.CreateStyled(RootFrame.XamlRoot, root.RequestedTheme);
+        dialog.Title = "Exit AmiReel?";
+        dialog.Content = "Are you sure you want to close the application?";
+        dialog.PrimaryButtonText = "Exit";
+        dialog.CloseButtonText = "Cancel";
+        dialog.DefaultButton = ContentDialogButton.Primary;
 
         ContentDialogResult result = await dialog.ShowAsync();
         if (result != ContentDialogResult.Primary) return;

AmiReel.WinUI/Package.appxmanifest

@@ -37,11 +37,11 @@
       <uap:VisualElements
         DisplayName="AmiReel"
         Description="AmiReel"
-        BackgroundColor="transparent"
+        BackgroundColor="#0E1525"
         Square150x150Logo="Assets\Square150x150Logo.png"
         Square44x44Logo="Assets\Square44x44Logo.png">
         <uap:DefaultTile Wide310x150Logo="Assets\Wide310x150Logo.png" />
-        <uap:SplashScreen Image="Assets\SplashScreen.png" />
+        <uap:SplashScreen Image="Assets\SplashScreen.png" BackgroundColor="#0E1525" />
       </uap:VisualElements>
     </Application>
   </Applications>

MainWindow.xaml

@@ -77,12 +77,12 @@
                     <Grid>
                         <Grid.RowDefinitions><RowDefinition Height="Auto"/><RowDefinition Height="98"/><RowDefinition Height="Auto"/></Grid.RowDefinitions>
                         <StackPanel Orientation="Horizontal" Margin="0,0,0,8">
-                            <Button Content="Add AVI files…" Click="AddInputs_Click" Margin="0,0,8,0"/>
+                            <Button Content="Add video files…" Click="AddInputs_Click" Margin="0,0,8,0"/>
                             <Button Content="Clear" Click="ClearInputs_Click"/>
                         </StackPanel>
                         <ListBox x:Name="InputList" Grid.Row="1" SelectionChanged="InputList_SelectionChanged"
                                  AllowDrop="True" DragEnter="InputList_DragEnter" DragOver="InputList_DragEnter" Drop="InputList_Drop"
-                                 ToolTip="Drag and drop AVI files here to add them"/>
+                                 ToolTip="Drag and drop video files here to add them"/>
                         <Button x:Name="PreviewSourceButton" Grid.Row="2" Content="Preview selected" Click="PreviewSource_Click"
                                 HorizontalAlignment="Left" Margin="0,10,0,0" IsEnabled="False"/>
                     </Grid>

MainWindow.xaml.cs

@@ -82,13 +82,13 @@ public partial class MainWindow : Window
     {
         if (!e.Data.GetDataPresent(DataFormats.FileDrop)) return;
         string[] files = (string[])e.Data.GetData(DataFormats.FileDrop)!;
-        foreach (string file in files.Where(f => string.Equals(Path.GetExtension(f), ".avi", StringComparison.OrdinalIgnoreCase)).OrderBy(NaturalKey))
+        foreach (string file in files.Where(Models.SupportedVideoFormats.IsSupported).OrderBy(NaturalKey))
             if (!_inputs.Contains(file, StringComparer.OrdinalIgnoreCase)) _inputs.Add(file);
     }
 
     private void AddInputs_Click(object sender, RoutedEventArgs e)
     {
-        OpenFileDialog dialog = new() { Filter = "AVI recordings (*.avi)|*.avi", Multiselect = true };
+        OpenFileDialog dialog = new() { Filter = $"Video files|{Models.SupportedVideoFormats.PickerFilter}", Multiselect = true };
         if (dialog.ShowDialog(this) != true) return;
         foreach (string file in dialog.FileNames.OrderBy(NaturalKey))
             if (!_inputs.Contains(file, StringComparer.OrdinalIgnoreCase)) _inputs.Add(file);

Models/SupportedVideoFormats.cs

@@ -0,0 +1,23 @@
+using System.IO;
+using System.Linq;
+
+namespace AmigaDB.VideoRenderer.Models;
+
+/// <summary>
+/// Video file extensions accepted as render sources. FFmpeg can demux far more than this,
+/// but this list covers what a screen/video capture workflow is realistically going to produce.
+/// </summary>
+public static class SupportedVideoFormats
+{
+    public static readonly IReadOnlyList<string> Extensions =
+    [
+        ".avi", ".mp4", ".m4v", ".mov", ".mkv", ".webm",
+        ".wmv", ".flv", ".mpg", ".mpeg", ".ts", ".3gp"
+    ];
+
+    public static bool IsSupported(string path) =>
+        Extensions.Contains(Path.GetExtension(path), StringComparer.OrdinalIgnoreCase);
+
+    /// <summary>Picker filter string, e.g. "*.avi;*.mp4;*.m4v;...".</summary>
+    public static string PickerFilter => string.Join(';', Extensions.Select(e => "*" + e));
+}

Services/RenderPipeline.cs

@@ -360,8 +360,8 @@ public sealed class RenderPipeline
 
     private static void Validate(RenderSettings s)
     {
-        if (s.InputFiles.Count == 0) throw new ArgumentException("Select at least one AVI input file.");
-        if (s.InputFiles.Any(f => !File.Exists(f))) throw new FileNotFoundException("One or more AVI files no longer exist.");
+        if (s.InputFiles.Count == 0) throw new ArgumentException("Select at least one video input file.");
+        if (s.InputFiles.Any(f => !File.Exists(f))) throw new FileNotFoundException("One or more input files no longer exist.");
         if (!string.IsNullOrWhiteSpace(s.EndCardPath) && !File.Exists(s.EndCardPath))
             throw new FileNotFoundException("End-card image was not found.");
         if (string.IsNullOrWhiteSpace(s.OutputDirectory)) throw new ArgumentException("Select an output directory.");