CatProejct/CatProject/App.xaml

<Application x:Class="CatProject.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:CatProject"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <Style TargetType="Button">
            <Setter Property="Width" Value="200"/>
            <Setter Property="Height" Value="25"/>
            <Setter Property="Background" Value="#C71585"/>
            <Setter Property="Foreground" Value="White"/>
            <Setter Property="HorizontalAlignment" Value="Right"/>
            <Setter Property="Margin" Value="3"/>
            <Setter Property="OverridesDefaultStyle" Value="True"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Button">
                        <Border Name="border"
                        BorderThickness="1"
                        Padding="4,2"
                        BorderBrush="#C71585"
                        CornerRadius="3"
                        Background="{TemplateBinding Background}">
                            <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center" />
                        </Border>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsMouseOver" Value="True">
                                <Setter TargetName="border" Property="BorderBrush" Value="Black"/>
                                <Setter Property="Foreground" Value="Black"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        
    </Application.Resources>
</Application>