Blissfully copied from Thomas's example and expanded on it:
<Window x:Class="BorderpressSpike.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<Style x:Key="NormalBorderStyle" TargetType="Border">
<Setter Property="BorderThickness" Value="2"/>
<Setter Property="BorderBrush" Value="Black"/>
</Style>
<Style x:Key="PressedBorderStyle" TargetType="Border">
<Setter Property="BorderThickness" Value="5"/>
<Setter Property="BorderBrush" Value="Red"/>
</Style>
</Window.Resources>
<StackPanel>
<Button Height="500">
<Button.Template>
<ControlTemplate TargetType="{x:Type Button}">
<Border Name="bd" Style="{StaticResource NormalBorderStyle}" >
<ContentPresenter/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsPressed" Value="True">
<Setter TargetName="bd"
Property="Style"
Value="{StaticResource PressedBorderStyle}" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Button.Template>
<Button Height="300">Inside Pressable Border</Button>
</Button>
</StackPanel>
</Window>
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