Implement design mode

osu.Game/Screens/Edit/Editor.cs

@@ -14,6 +14,7 @@ using OpenTK;
 using osu.Framework.Allocation;
 using osu.Game.Screens.Edit.Screens;
 using osu.Game.Screens.Edit.Screens.Compose;
+using osu.Game.Screens.Edit.Screens.Design;
 
 namespace osu.Game.Screens.Edit
 {
@@ -113,6 +114,9 @@ namespace osu.Game.Screens.Edit
                 case EditorScreenMode.Compose:
                     currentScreen = new Compose();
                     break;
+                case EditorScreenMode.Design:
+                    currentScreen = new Design();
+                    break;
                 default:
                     currentScreen = new EditorScreen();
                     break;

osu.Game/Screens/Edit/Screens/Design/Design.cs

@@ -0,0 +1,52 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Shapes;
+using osu.Game.Graphics.Sprites;
+using OpenTK.Graphics;
+
+namespace osu.Game.Screens.Edit.Screens.Design
+{
+    internal class Design : EditorScreen
+    {
+        public Design()
+        {
+            Add(new Container
+            {
+                RelativeSizeAxes = Axes.Both,
+                Children = new Drawable[]
+                {
+                    new Box
+                    {
+                        RelativeSizeAxes = Axes.Both,
+                        Colour = Color4.Black,
+                        Alpha = 0.35f
+                    },
+                    new Container
+                    {
+                        Anchor = Anchor.Centre,
+                        Origin = Anchor.Centre,
+                        AutoSizeAxes = Axes.Both,
+                        Children = new Drawable[]
+                        {
+                            new Box
+                            {
+                                RelativeSizeAxes = Axes.Both,
+                                Colour = Color4.Black,
+                                Alpha = 0.5f
+                            },
+                            new Container
+                            {
+                                AutoSizeAxes = Axes.Both,
+                                Padding = new MarginPadding(20),
+                                Child = new OsuSpriteText { Text = "Design screen" }
+                            }
+                        }
+                    }
+                }
+            });
+        }
+    }
+}

osu.Game/osu.Game.csproj

@@ -618,6 +618,7 @@
     <Compile Include="Screens\Edit\Menus\EditorMenuItem.cs" />
     <Compile Include="Screens\Edit\Menus\EditorMenuItemSpacer.cs" />
     <Compile Include="Screens\Edit\Menus\ScreenSelectionTabControl.cs" />
+    <Compile Include="Screens\Edit\Screens\Design\Design.cs" />
     <Compile Include="Screens\Edit\Screens\EditorScreen.cs" />
     <Compile Include="Screens\Edit\Screens\Compose\Compose.cs" />
     <Compile Include="Screens\Loader.cs" />