fix controller land layout

Author: boyan01

lib/panel/controller.dart

@@ -34,7 +34,7 @@ class DirectionController extends StatelessWidget {
     return Stack(
       alignment: Alignment.center,
       children: <Widget>[
-        SizedBox.expand(),
+        SizedBox.fromSize(size: _DIRECTION_BUTTON_SIZE * 2.8),
         Transform.rotate(
           angle: math.pi / 4,
           child: Column(

lib/panel/page_land.dart

@@ -45,6 +45,7 @@ class PageLand extends StatelessWidget {
                     ),
                     Spacer(),
                     DirectionController(),
+                    SizedBox(height: 30),
                   ],
                 ),
               ),