<Window x:Class="GadgetWindow"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  Height="300" Width="300"
  AllowsTransparency="True" WindowStyle="None" Background="Transparent"
  MouseLeftButtonDown="Window_MouseLeftButtonDown">
  <Grid>
    <Ellipse Fill="Red" Opacity="0.5" Margin="20">
      <Ellipse.Effect>
        <DropShadowEffect/>
      </Ellipse.Effect>
    </Ellipse>
    <Button Margin="100" Click="Button_Click">Zamknij</Button>
  </Grid>
</Window>
