Avalonia/src/Avalonia.Themes.Fluent/Controls/NotificationCard.xaml

<ResourceDictionary xmlns="https://github.com/avaloniaui"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    x:ClassModifier="internal">
  <Design.PreviewWith>
    <Border Padding="0" Background="White">
      <NotificationCard Content="Testing" />
    </Border>
  </Design.PreviewWith>
  <ControlTheme x:Key="{x:Type NotificationCard}" TargetType="NotificationCard">
    <Setter Property="UseLayoutRounding" Value="True"/>
    <Setter Property="Width" Value="350"/>
    <Setter Property="Foreground" Value="{DynamicResource NotificationCardForegroundBrush}"/>
    <Setter Property="RenderTransformOrigin" Value="50%,75%"/>
    <Setter Property="BorderThickness" Value="0" />
    <Setter Property="Background" Value="{DynamicResource NotificationCardBackgroundBrush}" />
    <Setter Property="CornerRadius" Value="{DynamicResource ControlCornerRadius}" />
    <Setter Property="Template">
      <ControlTemplate>
        <LayoutTransformControl Name="PART_LayoutTransformControl" UseRenderTransform="True">
          <Border CornerRadius="{TemplateBinding CornerRadius}" BoxShadow="0 6 8 0 #4F000000" Margin="5 5 5 10">
            <Border Background="{TemplateBinding Background}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    BorderThickness="{TemplateBinding BorderThickness}"
                    CornerRadius="{TemplateBinding CornerRadius}"
                    ClipToBounds="True">
              <DockPanel>
                <Panel x:Name="PART_HeaderBar" Height="4" Background="{DynamicResource NotificationCardProgressBackgroundBrush}" DockPanel.Dock="Top" />
                <ContentControl Name="PART_Content" MinHeight="64" Content="{TemplateBinding Content}" />
              </DockPanel>
            </Border>
          </Border>
        </LayoutTransformControl>
      </ControlTemplate>
    </Setter>

    <ControlTheme.Animations>
      <Animation Duration="0:0:0.45" Easing="QuadraticEaseIn" FillMode="Forward">
        <KeyFrame Cue="0%">
          <Setter Property="Opacity" Value="0"/>
          <Setter Property="TranslateTransform.Y" Value="20"/>
          <Setter Property="ScaleTransform.ScaleX" Value="0.85"/>
          <Setter Property="ScaleTransform.ScaleY" Value="0.85"/>
        </KeyFrame>
        <KeyFrame Cue="30%">
          <Setter Property="TranslateTransform.Y" Value="-20"/>
        </KeyFrame>
        <KeyFrame Cue="100%">
          <Setter Property="Opacity" Value="1"/>
          <Setter Property="TranslateTransform.Y" Value="0"/>
          <Setter Property="ScaleTransform.ScaleX" Value="1"/>
          <Setter Property="ScaleTransform.ScaleY" Value="1"/>
        </KeyFrame>
      </Animation>
    </ControlTheme.Animations>

    <Style Selector="^[IsClosing=true] /template/ LayoutTransformControl#PART_LayoutTransformControl">
      <Setter Property="RenderTransformOrigin" Value="50%,0%"/>
      <Style.Animations>
        <Animation Duration="0:0:0.75" Easing="QuadraticEaseOut" FillMode="Forward">
          <KeyFrame Cue="0%">
            <Setter Property="TranslateTransform.X" Value="0"/>
            <Setter Property="ScaleTransform.ScaleY" Value="1"/>
          </KeyFrame>
          <KeyFrame Cue="70%">
            <Setter Property="TranslateTransform.X" Value="800"/>
            <Setter Property="ScaleTransform.ScaleY" Value="1"/>
          </KeyFrame>
          <KeyFrame Cue="100%">
            <Setter Property="ScaleTransform.ScaleY" Value="0"/>
            <Setter Property="TranslateTransform.X" Value="800"/>
          </KeyFrame>
        </Animation>
      </Style.Animations>
    </Style>

    <Style Selector="^[IsClosing=true]">
      <Style.Animations>
        <Animation Duration="0:0:1.25" Easing="QuadraticEaseOut" FillMode="Forward">
          <KeyFrame Cue="100%">
            <Setter Property="IsClosed" Value="True"/>
          </KeyFrame>
        </Animation>
      </Style.Animations>
    </Style>

    <Style Selector="^:information /template/ Panel#PART_HeaderBar">
      <Setter Property="Background" Value="{DynamicResource NotificationCardInformationBackgroundBrush}"/>
    </Style>
    <Style Selector="^:success /template/ Panel#PART_HeaderBar">
      <Setter Property="Background" Value="{DynamicResource NotificationCardSuccessBackgroundBrush}"/>
    </Style>
    <Style Selector="^:warning /template/ Panel#PART_HeaderBar">
      <Setter Property="Background" Value="{DynamicResource NotificationCardWarningBackgroundBrush}"/>
    </Style>
    <Style Selector="^:error /template/ Panel#PART_HeaderBar">
      <Setter Property="Background" Value="{DynamicResource NotificationCardErrorBackgroundBrush}"/>
    </Style>
  </ControlTheme>
</ResourceDictionary>