Add basic background display system.

osu.Game/Graphics/Background/Background.cs

@@ -0,0 +1,36 @@
+//Copyright (c) 2007-2016 ppy Pty Ltd <contact@ppy.sh>.
+//Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Sprites;
+using osu.Game.Graphics.Containers;
+using OpenTK;
+using OpenTK.Graphics;
+
+namespace osu.Game.Graphics.Background
+{
+    class Background : OsuLargeContainer
+    {
+        protected Sprite BackgroundSprite;
+
+        public override void Load()
+        {
+            base.Load();
+
+            Add(BackgroundSprite = new Sprite
+            {
+                Texture = Game.Textures.Get(@"Menu/background"),
+                Anchor = Anchor.Centre,
+                Origin = Anchor.Centre,
+                Colour = Color4.DarkGray
+            });
+        }
+
+        protected override void Update()
+        {
+            base.Update();
+            BackgroundSprite.Scale = new Vector2(Math.Max(ActualSize.X / BackgroundSprite.Size.X, ActualSize.Y / BackgroundSprite.Size.Y));
+        }
+    }
+}

osu.Game/Graphics/Containers/ParallaxContainer.cs

@@ -0,0 +1,40 @@
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics;
+using osu.Framework.Input;
+using OpenTK;
+
+namespace osu.Game.Graphics.Containers
+{
+    class ParallaxContainer : LargeContainer
+    {
+        public float ParallaxAmount = 0.02f;
+
+        public override bool Contains(Vector2 screenSpacePos) => true;
+
+        private Container content = new LargeContainer()
+        {
+            Anchor = Anchor.Centre,
+            Origin = Anchor.Centre
+        };
+
+        protected override Container AddTarget => content;
+
+        public override void Load()
+        {
+            base.Load();
+            Add(content);
+        }
+
+        protected override bool OnMouseMove(InputState state)
+        {
+            content.Position = (state.Mouse.Position - ActualSize / 2) * ParallaxAmount;
+            return base.OnMouseMove(state);
+        }
+
+        protected override void Update()
+        {
+            base.Update();
+            content.Scale = new Vector2(1 + ParallaxAmount);
+        }
+    }
+}

osu.Game/OsuGame.cs

@@ -5,7 +5,10 @@ using osu.Game.Configuration;
 using osu.Game.GameModes.Menu;
 using OpenTK;
 using osu.Framework.Graphics;
+using osu.Framework.Graphics.Sprites;
 using osu.Framework.OS;
+using osu.Game.Graphics.Background;
+using osu.Game.Graphics.Containers;
 
 namespace osu.Game
 {
@@ -22,7 +25,15 @@ namespace osu.Game
         {
             base.Load();
 
-            Add(new MainMenu());
+            Add(new Drawable[] {
+                new ParallaxContainer
+                {
+                    Children = new [] {
+                        new Background()
+                    }
+                },
+                new MainMenu()
+            });
         }
 
         protected override void Dispose(bool isDisposing)

osu.Game/osu.Game.csproj

@@ -62,6 +62,8 @@
     <Compile Include="GameModes\Direct\OnlineListing.cs" />
     <Compile Include="GameModes\Play\SongSelectPlay.cs" />
     <Compile Include="GameModes\Edit\SongSelectEdit.cs" />
+    <Compile Include="Graphics\Background\Background.cs" />
+    <Compile Include="Graphics\Containers\ParallaxContainer.cs" />
     <Compile Include="Graphics\Containers\OsuContainer.cs" />
     <Compile Include="Graphics\Containers\OsuGameMode.cs" />
     <Compile Include="Graphics\Containers\OsuLargeContainer.cs" />