Avalonia/samples/RenderDemo/Pages/SpringAnimationsPage.xaml

<UserControl 
  xmlns="https://github.com/avaloniaui" 
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
  x:Class="RenderDemo.Pages.SpringAnimationsPage"
  MaxWidth="600">
  <UserControl.Resources>
    <SpringEasing x:Key="SpringEasing" Mass="1" Stiffness="2000" Damping="20" InitialVelocity="0" />
  </UserControl.Resources>
  <UserControl.Styles>
    <Style Selector="Border.spring">
      <Style.Animations>
        <Animation Duration="0:0:0.900" 
                   IterationCount="Infinite" 
                   PlaybackDirection="Normal" 
                   Easing="{DynamicResource SpringEasing}">
          <KeyFrame Cue="0%" KeySpline="">
            <Setter Property="TranslateTransform.X" Value="-300"/>
          </KeyFrame>
          <KeyFrame Cue="100%">
            <Setter Property="TranslateTransform.X" Value="0" />
          </KeyFrame>
        </Animation>
      </Style.Animations>
    </Style>
  </UserControl.Styles>
  <Grid>
    <Border Classes="spring" Background="Red" Width="50" Height="50">
      <Border.RenderTransform>
        <TransformGroup>
          <TranslateTransform />
        </TransformGroup>
      </Border.RenderTransform>
    </Border>
  </Grid>
</UserControl>