XAML. Рамка кнопок

Есть такой код на XAML

<Window x:Class="ToDo.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    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"
    xmlns:local="clr-namespace:ToDo"
    mc:Ignorable="d"
    Title="MainWindow" Height="584.517" Width="1039.419" WindowStyle="None">    
<Grid>
    <Grid Height="50" VerticalAlignment ="Top" Background="#FFF9B3AA">
        <Button HorizontalAlignment="Right" Height="25" Width="25" Margin="0,0,10,0" Background="{x:Null}">
            <Image Source="Images/close.png" Stretch="Fill"></Image>
        </Button>
    </Grid>
    <Grid Width="80" HorizontalAlignment = "Left" Background="#FFF46F5E">
        <StackPanel HorizontalAlignment="Center">
            <Button  Height="35" Width="35" Margin="0, 7.5 ,0 ,10" Background="{x:Null}">
                <Image Source="Images/menu.png" Stretch="Fill"></Image>
            </Button>
            <Button Height="35" Width="35" Margin="0, 10 ,0 ,10" Background="{x:Null}" >
                <Image Source="Images/plus.png" Stretch="Fill"></Image>
            </Button>
            <Button Height="35" Width="35" Margin="0, 10 ,0 ,10" Background="{x:Null}">
                <Image Source="Images/todo.png" Stretch="Fill"></Image>
            </Button>                
            <Button Height="35" Width="35" Margin="0, 350 ,0 ,10" Background="{x:Null}">
                <Image Source="Images/setting.png" Stretch="Fill"></Image>
            </Button>
        </StackPanel>
    </Grid>
    <Grid Width="300" HorizontalAlignment="Left" Margin="80, 50, 0, 0" Background="#FFF89284"></Grid>
    <Grid Width="651" HorizontalAlignment="Left" Margin="380, 50, 0 0" Background="White"></Grid>
    </Grid>

Получился такой интерфейс

Вопрос такой: как убрать рамки кнопок, чтобы были только иконки? И как закруглить углы окна? Подскажите пожалуйста