<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="using:AvaloniaTestApp"
        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
        x:Class="AvaloniaTestApp.MainWindow"
        Title="AvaloniaTestApp">
  <Window.Styles>
    <Style Selector="Button">
      <Style.Animations>
        <Animation FillMode="None"
                   IterationCount="Infinite"
                   PlaybackDirection="Normal"
                   Duration="0:0:1.5">
          <KeyFrame Cue="0%">
            <Setter Property="Opacity" Value="0.2" />
          </KeyFrame>
          <KeyFrame Cue="20%">
            <Setter Property="Opacity" Value="0.1" />
          </KeyFrame>
          <KeyFrame Cue="50%">
            <Setter Property="Opacity" Value="0.05" />
          </KeyFrame>
          <KeyFrame Cue="80%">
            <Setter Property="Opacity" Value="0.1" />
          </KeyFrame>
          <KeyFrame Cue="100%">
            <Setter Property="Opacity" Value="0.2" />
          </KeyFrame>
        </Animation>

      </Style.Animations>
    </Style>
  </Window.Styles>
  <Button Background="Red" Width="100" Height="100"/>
</Window>