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

<ResourceDictionary xmlns="https://github.com/avaloniaui"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    x:ClassModifier="internal">
  <ControlTheme x:Key="{x:Type NotificationCard}"
                TargetType="NotificationCard">
    <Setter Property="Background" Value="{DynamicResource NotificationCardBackgroundBrush}" />
    <Setter Property="UseLayoutRounding" Value="True" />
    <Setter Property="Width" Value="350" />
    <Setter Property="FontSize" Value="{DynamicResource FontSizeLarge}" />
    <Setter Property="Foreground" Value="White" />
    <Setter Property="RenderTransformOrigin" Value="50%,75%" />
    <Setter Property="Template">
      <ControlTemplate>
        <LayoutTransformControl Name="PART_LayoutTransformControl"
                                UseRenderTransform="True">
          <Border Margin="8,8,0,0"
                  Background="{TemplateBinding Background}"
                  BorderBrush="{TemplateBinding BorderBrush}"
                  BorderThickness="{TemplateBinding BorderThickness}"
                  CornerRadius="{TemplateBinding CornerRadius}">
            <ContentControl Name="PART_Content"
                            MinHeight="150"
                            Content="{TemplateBinding Content}" />
          </Border>
        </LayoutTransformControl>
      </ControlTemplate>
    </Setter>
    <Style Selector="^">
      <Style.Animations>
        <Animation Easing="QuadraticEaseIn"
                   FillMode="Forward"
                   Duration="0:0:0.45">
          <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>
      </Style.Animations>
    </Style>

    <Style Selector="^[IsClosing=true] /template/ LayoutTransformControl#PART_LayoutTransformControl">
      <Setter Property="RenderTransformOrigin" Value="50%,0%" />
      <Style.Animations>
        <Animation Easing="QuadraticEaseOut"
                   FillMode="Forward"
                   Duration="0:0:0.75">
          <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 Easing="QuadraticEaseOut"
                   FillMode="Forward"
                   Duration="0:0:1.25">
          <KeyFrame Cue="100%">
            <Setter Property="IsClosed" Value="True" />
          </KeyFrame>
        </Animation>
      </Style.Animations>
    </Style>

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