html round buttons

1.btn {
2  display:block;
3  height: 300px;
4  width: 300px;
5  border-radius: 50%;
6  border: 1px solid red;
7  
8}

1<button style="border-radius: 12px">A Little Round</button>

1<Style TargetType="Button" x:Key="RoundButton">
2    <Style.Resources>
3        <Style TargetType="Border">
4            <Setter Property="CornerRadius" Value="5" />
5        </Style>
6    </Style.Resources>
7</Style>
8