MainWindow.axaml

<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"
        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
        x:Class="PulsarRemoteAPI.MainWindow"
        Title="PulsarRemoteAPI" Width="560" Height="840">
  <Grid Background="#e6e6e6" Margin="0,0,0,0">
  <Border Margin="10,10,10,0" BorderBrush="Black" BorderThickness="1" HorizontalAlignment="Center" VerticalAlignment="Center">
    <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center" Background="#e6e6e6" >
      <StackPanel Orientation="Vertical" HorizontalAlignment="Center">
        <TextBlock Foreground="White" Background="Black" Text="Search Accounts in Pulsar" FontSize="18" TextAlignment="Center" Margin="0,0,0,10"/>
        <StackPanel Orientation="Horizontal" Width="500">
          <TextBox Name="textBox_Query" Watermark="Search account names..." Margin="10" Width="390"/>
          <Button Name="button_Search" Foreground="White" Background="Black" Content="Search" />
        </StackPanel>
      </StackPanel>
      <StackPanel Orientation="Vertical" Margin="0,20,0,0">
      	<StackPanel>
          <TextBlock Foreground="Black" Text="Request" FontSize="18" TextAlignment="Center" Margin="0,0,0,10"/>
          <TextBox Name="textBox_Request" TextWrapping="Wrap" Watermark="Request will appear here" Margin="10,5,10,5" Width="480" Height="300"/>
        </StackPanel>
        <StackPanel>
          <TextBlock  Foreground="Black" Text="Results" FontSize="18" TextAlignment="Center" Margin="0,0,0,10"/>
          <TextBox Name="textBox_Result" TextWrapping="Wrap" Watermark="Results will appear here" Margin="10,5,10,5" Width="480" Height="300"/>
        </StackPanel>
      </StackPanel>
    </StackPanel>
  </Border>
  </Grid>
</Window>