Mode -> Ruleset.

osu.Game.Rulesets.Osu/Objects/Drawables/Pieces/CirclePiece.cs

@@ -0,0 +1,58 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Graphics.Textures;
+using osu.Framework.Input;
+using OpenTK;
+
+namespace osu.Game.Rulesets.Osu.Objects.Drawables.Pieces
+{
+    public class CirclePiece : Container
+    {
+        private readonly Sprite disc;
+
+
+        public Func<bool> Hit;
+
+        public CirclePiece()
+        {
+            Size = new Vector2((float)OsuHitObject.OBJECT_RADIUS * 2);
+            Masking = true;
+            CornerRadius = Size.X / 2;
+
+            Anchor = Anchor.Centre;
+            Origin = Anchor.Centre;
+
+            Children = new Drawable[]
+            {
+                disc = new Sprite
+                {
+                    Anchor = Anchor.Centre,
+                    Origin = Anchor.Centre
+                },
+                new TrianglesPiece
+                {
+                    RelativeSizeAxes = Axes.Both,
+                    BlendingMode = BlendingMode.Additive,
+                    Alpha = 0.5f,
+                }
+            };
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(TextureStore textures)
+        {
+            disc.Texture = textures.Get(@"Play/osu/disc");
+        }
+
+        protected override bool OnMouseDown(InputState state, MouseDownEventArgs args)
+        {
+            return Hit?.Invoke() ?? false;
+        }
+    }
+}