Let us start here, from square one. No, from Zero!

overlay/windows/keypad.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "overlay/window.h"
+
+namespace overlay::windows {
+
+    class Keypad : public Window {
+    private:
+
+        size_t unit = 0;
+
+    public:
+
+        Keypad(SpiceOverlay *overlay, size_t unit);
+        ~Keypad() override;
+
+        void build_content() override;
+    };
+}