LanMountainDesktop/LanMountainDesktop/Views/NotificationWindow.axaml

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="using:LanMountainDesktop.ViewModels"
        xmlns:fi="using:FluentIcons.Avalonia"
        xmlns:controls="using:LanMountainDesktop.Controls"
        x:Class="LanMountainDesktop.Views.NotificationWindow"
        x:DataType="vm:NotificationViewModel"
        SystemDecorations="None"
        Background="Transparent"
        ShowInTaskbar="False"
        Topmost="True"
        CanResize="False"
        SizeToContent="WidthAndHeight"
        TransparencyLevelHint="Transparent"
        ExtendClientAreaToDecorationsHint="True"
        ExtendClientAreaChromeHints="NoChrome"
        ExtendClientAreaTitleBarHeightHint="-1">

    <Window.Styles>
        <Style Selector="Border.notification-card">
            <Setter Property="Background" Value="{DynamicResource AdaptiveGlassPanelBackgroundBrush}" />
            <Setter Property="BorderBrush" Value="{DynamicResource AdaptiveGlassPanelBorderBrush}" />
            <Setter Property="BorderThickness" Value="1.2" />
            <Setter Property="CornerRadius" Value="18" />
            <Setter Property="Padding" Value="16,12" />
        </Style>

        <Style Selector="TextBlock.notification-title">
            <Setter Property="FontSize" Value="14" />
            <Setter Property="FontWeight" Value="SemiBold" />
            <Setter Property="Foreground" Value="{DynamicResource AdaptiveTextPrimaryBrush}" />
            <Setter Property="TextWrapping" Value="Wrap" />
        </Style>

        <Style Selector="TextBlock.notification-message">
            <Setter Property="FontSize" Value="13" />
            <Setter Property="FontWeight" Value="Regular" />
            <Setter Property="Foreground" Value="{DynamicResource AdaptiveTextSecondaryBrush}" />
            <Setter Property="TextWrapping" Value="Wrap" />
            <Setter Property="MaxWidth" Value="260" />
            <Setter Property="Margin" Value="0,2,0,0" />
        </Style>

        <Style Selector="Border.notification-severity-indicator">
            <Setter Property="Width" Value="4" />
            <Setter Property="CornerRadius" Value="2" />
            <Setter Property="Margin" Value="0,4,12,4" />
            <Setter Property="VerticalAlignment" Value="Stretch" />
        </Style>
    </Window.Styles>

    <Border Margin="12"
            Classes="notification-card"
            x:Name="CardBorder"
            PointerPressed="OnCardPointerPressed"
            PointerEntered="OnCardPointerEntered"
            PointerExited="OnCardPointerExited"
            Cursor="Hand">
        <Grid ColumnDefinitions="Auto,Auto,*" ColumnSpacing="0">
            <Border Grid.Column="0"
                    Classes="notification-severity-indicator"
                    x:Name="SeverityIndicator"
                    Background="#FF3B82F6" />

            <Border Grid.Column="1"
                    Width="40"
                    Height="40"
                    VerticalAlignment="Center"
                    x:Name="IconContainer">
                <Panel>
                    <Image x:Name="IconImage"
                           Stretch="Uniform"
                           Source="{Binding Icon}"
                           IsVisible="{Binding Icon, Converter={x:Static ObjectConverters.IsNotNull}}" />
                    <fi:SymbolIcon x:Name="DefaultIcon"
                                   FontSize="28"
                                   Symbol="Info"
                                   IsVisible="{Binding Icon, Converter={x:Static ObjectConverters.IsNull}}"
                                   Foreground="{DynamicResource AdaptiveTextPrimaryBrush}" />
                </Panel>
            </Border>

            <StackPanel Grid.Column="2"
                        Margin="12,0,0,0"
                        VerticalAlignment="Center"
                        Spacing="2">
                <TextBlock Text="{Binding Title}"
                           Classes="notification-title" />
                <TextBlock Text="{Binding Message}"
                           Classes="notification-message"
                           IsVisible="{Binding Message, Converter={x:Static StringConverters.IsNotNullOrEmpty}}" />
            </StackPanel>
        </Grid>
    </Border>
</Window>