Windows 8.1 layout RememberMe

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

    <Grid>
        <Grid.Background>
            <ImageBrush Stretch="Fill" ImageSource="Assets/BG-W.png"/>
        </Grid.Background>
        <Grid.RowDefinitions>
            <RowDefinition Height="240"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="100"/>
            <RowDefinition Height="100"/>
            <RowDefinition Height="100"/>
            <RowDefinition Height="2*"/>
        </Grid.RowDefinitions>
        <StackPanel VerticalAlignment="Center" Margin="0, 20, 0, 0">
            <TextBlock Text="REMEMBER" FontSize="80" TextAlignment="Center" VerticalAlignment="Center" FontFamily="Quartz MS" FontWeight="Bold" Foreground="#FFDFECDC" />
            <TextBlock Text="ME" FontSize="80" TextAlignment="Center" VerticalAlignment="Center" FontFamily="Quartz MS" FontWeight="Bold" Foreground="#FFDFECDC" />
        </StackPanel>
        <Image x:Name="btn_start" Grid.Row="2" Height="95" Width="260" HorizontalAlignment="Center" Source="Asset/btn-start.png" />
        <Image x:Name="btn_score" Grid.Row="3" Height="95" Width="260" HorizontalAlignment="Center" Source="Asset/btn-score.png" />
        <Image x:Name="btn_about" Grid.Row="4" Tapped="btn_about_Tapped" Height="95" Width="260" HorizontalAlignment="Center" Source="Asset/btn-about.png"/>
    </Grid>
</Page>