MainPage.xaml

<Page
    x:Class="LuaBox.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:LuaBox"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition Height="32"/>
        </Grid.RowDefinitions>

        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="6*"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>

        <TextBlock x:Name="ResultLabel" Grid.Row="0" Grid.Column="0"/>
        <TextBox x:Name="InputLine" PlaceholderText=">" Grid.Row="1" Grid.Column="0" KeyDown="InputLine_KeyDown"/>
        <Button Content="Enter" VerticalAlignment="Top" Click="Button_Click" HorizontalAlignment="Stretch" Grid.Row="1" Grid.Column="1"/>
    </Grid>
</Page>