<Grid xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      Background="#FF0A0B12">
    <!-- Large centred disc with a plain radial-fill ellipse. Black core
         fading through orange to a cool rim — legible on a compressed
         screenshot and exercises the PATH_AA_RADIAL path (ellipses always
         take the AA path in Noesis). -->
    <Ellipse Width="360" Height="360"
             HorizontalAlignment="Center" VerticalAlignment="Center">
        <Ellipse.Fill>
            <RadialGradientBrush GradientOrigin="0.5,0.5" Center="0.5,0.5"
                                 RadiusX="0.5" RadiusY="0.5">
                <GradientStop Offset="0.0" Color="#FF000000"/>
                <GradientStop Offset="0.5" Color="#FFFF8800"/>
                <GradientStop Offset="1.0" Color="#FF3355AA"/>
            </RadialGradientBrush>
        </Ellipse.Fill>
    </Ellipse>

    <!-- Offset-origin radial on a rectangle — validates the focal `dd`
         term in the shader, since the origin ≠ centre. -->
    <Rectangle Width="200" Height="120"
               HorizontalAlignment="Left" VerticalAlignment="Top"
               Margin="24,24,0,0">
        <Rectangle.Fill>
            <RadialGradientBrush GradientOrigin="0.2,0.3" Center="0.5,0.5"
                                 RadiusX="0.6" RadiusY="0.6">
                <GradientStop Offset="0.0" Color="#FFFFFFFF"/>
                <GradientStop Offset="1.0" Color="#FF1F2633"/>
            </RadialGradientBrush>
        </Rectangle.Fill>
    </Rectangle>
</Grid>
