feat: prototype.

src/Ursa.Themes.Semi/Controls/NumPad.axaml

@@ -0,0 +1,14 @@
+<ResourceDictionary xmlns="https://github.com/avaloniaui"
+                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+                    xmlns:u="https://irihi.tech/ursa">
+    <!-- Add Resources Here -->
+    <ControlTheme x:Key="{x:Type u:NumPad}" TargetType="{x:Type u:NumPad}">
+        <Setter Property="Template">
+            <ControlTemplate TargetType="u:NumPad">
+                <Border Padding="48">
+                    <Button Focusable="False" Name="{x:Static u:NumPad.PART_Seven}" Content="7" Width="32"></Button>
+                </Border>
+            </ControlTemplate>
+        </Setter>
+    </ControlTheme>
+</ResourceDictionary>