initial setup with top-bottom approach

src/Main.java

@@ -0,0 +1,20 @@
+import java.awt.event.WindowAdapter;
+import java.awt.event.WindowEvent;
+
+public class Main {
+    public static void main(String[] args) {
+        Window win = new Window();
+        win.setVisible(true);
+        win.setSize(640, 480);
+        win.setPositionRelativeTo(null);
+        win.addWindowListener(new WindowAdapter() {
+            @Override
+            public void windowClosing(WindowEvent e) {
+                win.dispose();
+            }
+        });
+
+        Button button = new Button();
+        win.addVisual(button);
+    }
+}