aistudio-wpf-diagram/AIStudio.Wpf.DiagramDesigner/Styles/ToggleButton.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

    <Style x:Key="AIStudio.DiagramDesigner.Styles.ToggleButton.Flat" TargetType="{x:Type ToggleButton}">
        <Setter Property="Background" Value="LightGray" />
        <Setter Property="Foreground" Value="Black" />
        <Setter Property="HorizontalContentAlignment" Value="Center"/>
        <Setter Property="VerticalContentAlignment" Value="Center"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ToggleButton}">
                    <Grid ClipToBounds="True" Width="{TemplateBinding Width}" Height="{TemplateBinding Height}">
                        <VisualStateManager.VisualStateGroups>
                            <VisualStateGroup x:Name="CommonStates">
                                <VisualState x:Name="Normal"/>
                                <VisualState x:Name="Disabled">
                                    <Storyboard>
                                        <DoubleAnimation Duration="0" To="0.38" Storyboard.TargetProperty="(UIElement.Opacity)" />
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                            <VisualStateGroup x:Name="CheckStates">
                                <VisualStateGroup.Transitions>
                                    <VisualTransition From="*" To="Checked">
                                        <Storyboard>
                                            <DoubleAnimationUsingKeyFrames Duration="0:0:0.2" Storyboard.TargetProperty="ScaleX" Storyboard.TargetName="CheckedEllipseScale">
                                                <LinearDoubleKeyFrame Value="0" KeyTime="0:0:0.0" />
                                                <LinearDoubleKeyFrame Value="1.0" KeyTime="0:0:0.1" />
                                            </DoubleAnimationUsingKeyFrames>
                                            <DoubleAnimationUsingKeyFrames Duration="0:0:0.2" Storyboard.TargetProperty="ScaleY" Storyboard.TargetName="CheckedEllipseScale">
                                                <LinearDoubleKeyFrame Value="0" KeyTime="0:0:0.0" />
                                                <LinearDoubleKeyFrame Value="1.0" KeyTime="0:0:0.1" />
                                            </DoubleAnimationUsingKeyFrames>
                                        </Storyboard>
                                    </VisualTransition>
                                    <VisualTransition From="Checked" To="Unchecked">
                                        <Storyboard>
                                            <DoubleAnimationUsingKeyFrames Duration="0:0:0.2" Storyboard.TargetProperty="ScaleX" Storyboard.TargetName="CheckedEllipseScale">
                                                <LinearDoubleKeyFrame Value="1.0" KeyTime="0:0:0.0" />
                                                <LinearDoubleKeyFrame Value="0" KeyTime="0:0:0.1" />
                                            </DoubleAnimationUsingKeyFrames>
                                            <DoubleAnimationUsingKeyFrames Duration="0:0:0.2" Storyboard.TargetProperty="ScaleY" Storyboard.TargetName="CheckedEllipseScale">
                                                <LinearDoubleKeyFrame Value="1.0" KeyTime="0:0:0.0" />
                                                <LinearDoubleKeyFrame Value="0" KeyTime="0:0:0.1" />
                                            </DoubleAnimationUsingKeyFrames>
                                        </Storyboard>
                                    </VisualTransition>
                                </VisualStateGroup.Transitions>
                                <VisualState x:Name="Checked">
                                    <Storyboard>
                                        <DoubleAnimation Duration="0" Storyboard.TargetProperty="ScaleX" Storyboard.TargetName="CheckedEllipseScale" To="1.0" />
                                        <DoubleAnimation Duration="0" Storyboard.TargetProperty="ScaleY" Storyboard.TargetName="CheckedEllipseScale" To="1.0" />
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="Unchecked">
                                    <Storyboard>
                                        <DoubleAnimation Duration="0" Storyboard.TargetProperty="ScaleX" Storyboard.TargetName="CheckedEllipseScale" To="0" />
                                        <DoubleAnimation Duration="0" Storyboard.TargetProperty="ScaleY" Storyboard.TargetName="CheckedEllipseScale" To="0" />
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                        </VisualStateManager.VisualStateGroups>
                        <Rectangle Fill="Transparent" x:Name="HoverEllipse" Stroke="Transparent" StrokeThickness="1" />
                        <Rectangle Fill="{TemplateBinding Background}" x:Name="CheckedEllipse" RenderTransformOrigin="0.5, 0.5">
                            <Rectangle.RenderTransform>
                                <ScaleTransform CenterX="0.5" CenterY="0.5" ScaleX="1.0" ScaleY="1.0" x:Name="CheckedEllipseScale"/>
                            </Rectangle.RenderTransform>
                        </Rectangle>
                        <ContentPresenter x:Name="contentPresenter" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="true">
                            <Setter Property="Stroke" TargetName="HoverEllipse" Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Background}" />
                        </Trigger>

                        <Trigger Property="IsChecked" Value="True">
                            <Setter Property="Background" Value="#f1f1f1"/>
                        </Trigger>

                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Style.Triggers>           
            <Trigger Property="IsMouseOver" Value="True">
                <Setter Property="Opacity" Value=".9"/>
            </Trigger>
            <Trigger Property="IsPressed" Value="True">
                <Setter Property="Opacity" Value=".6"/>
            </Trigger>
            <Trigger Property="IsEnabled" Value="False">
                <Setter Property="Opacity" Value="0.5"/>
            </Trigger>
        </Style.Triggers>
    </Style>
</ResourceDictionary>