LEA2/CheckersSpielBot/LoginWindow.xaml

<Window x:Class="CheckersSpielBot.LoginWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Checkers" Height="420" Width="360"
        WindowStartupLocation="CenterScreen"
        ResizeMode="NoResize"
        Background="#222">

    <Window.Resources>
        <Style x:Key="InputStyle" TargetType="TextBox">
            <Setter Property="Background"      Value="#333"/>
            <Setter Property="Foreground"      Value="White"/>
            <Setter Property="BorderBrush"     Value="#555"/>
            <Setter Property="BorderThickness" Value="1"/>
            <Setter Property="Padding"         Value="8,6"/>
            <Setter Property="FontSize"        Value="13"/>
            <Setter Property="Height"          Value="36"/>
            <Setter Property="CaretBrush"      Value="White"/>
        </Style>

        <Style x:Key="PasswordStyle" TargetType="PasswordBox">
            <Setter Property="Background"      Value="#333"/>
            <Setter Property="Foreground"      Value="White"/>
            <Setter Property="BorderBrush"     Value="#555"/>
            <Setter Property="BorderThickness" Value="1"/>
            <Setter Property="Padding"         Value="8,6"/>
            <Setter Property="FontSize"        Value="13"/>
            <Setter Property="Height"          Value="36"/>
        </Style>

        <Style x:Key="PrimaryBtn" TargetType="Button">
            <Setter Property="Background"      Value="#CC2222"/>
            <Setter Property="Foreground"      Value="White"/>
            <Setter Property="FontSize"        Value="13"/>
            <Setter Property="FontWeight"      Value="SemiBold"/>
            <Setter Property="BorderThickness" Value="0"/>
            <Setter Property="Height"          Value="42"/>
            <Setter Property="Cursor"          Value="Hand"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Button">
                        <Border Background="{TemplateBinding Background}" CornerRadius="5">
                            <ContentPresenter HorizontalAlignment="Center"
                                              VerticalAlignment="Center"/>
                        </Border>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsMouseOver" Value="True">
                                <Setter Property="Background" Value="#AA1111"/>
                            </Trigger>
                            <Trigger Property="IsPressed" Value="True">
                                <Setter Property="Background" Value="#880000"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

        <Style x:Key="TabBtn" TargetType="Button">
            <Setter Property="Background"      Value="Transparent"/>
            <Setter Property="Foreground"      Value="#888"/>
            <Setter Property="FontSize"        Value="14"/>
            <Setter Property="FontWeight"      Value="SemiBold"/>
            <Setter Property="BorderThickness" Value="0"/>
            <Setter Property="Cursor"          Value="Hand"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Button">
                        <Border Background="Transparent"
                                BorderBrush="#555"
                                BorderThickness="0,0,0,2"
                                Padding="0,0,0,4">
                            <ContentPresenter HorizontalAlignment="Center"/>
                        </Border>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsMouseOver" Value="True">
                                <Setter Property="Foreground" Value="White"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>

    <Grid Margin="30">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="24"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="20"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="10"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="10"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="10"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="14"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <!-- Title -->
        <TextBlock Grid.Row="0"
                   Text="CHECKERS"
                   Foreground="White"
                   FontSize="24"
                   FontWeight="Bold"
                   HorizontalAlignment="Center"/>

        <!-- Tab switcher -->
        <Grid Grid.Row="2">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            <Button Grid.Column="0"
                    x:Name="TabLoginBtn"
                    Content="Login"
                    Style="{StaticResource TabBtn}"
                    Click="SwitchToLogin"/>

            <Button Grid.Column="1"
                    x:Name="TabRegisterBtn"
                    Content="Register"
                    Style="{StaticResource TabBtn}"
                    Click="SwitchToRegister"/>
        </Grid>

        <!-- Username -->
        <TextBlock Grid.Row="4"
                   Text="Username"
                   Foreground="#AAA"
                   FontSize="12"/>

        <TextBox Grid.Row="6"
                 x:Name="UsernameBox"
                 Style="{StaticResource InputStyle}"/>

        <!-- Password -->
        <TextBlock Grid.Row="8"
                   Text="Password"
                   Foreground="#AAA"
                   FontSize="12"/>

        <PasswordBox Grid.Row="10"
                     x:Name="PwdBox"
                     Style="{StaticResource PasswordStyle}"/>

        <!-- Error / success -->
        <TextBlock Grid.Row="12"
                   x:Name="ErrorText"
                   Foreground="#FF6666"
                   FontSize="12"
                   TextWrapping="Wrap"
                   HorizontalAlignment="Center"/>

        <Button Grid.Row="12"
                x:Name="ActionBtn"
                Content="Login"
                Style="{StaticResource PrimaryBtn}"
                Margin="0,24,0,0"
                Click="ActionBtn_Click"/>
    </Grid>
</Window>