Move piece files in Osu ruleset

osu.Game.Rulesets.Osu/Skinning/Default/RingPiece.cs

@@ -0,0 +1,33 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osuTK;
+using osuTK.Graphics;
+using osu.Framework.Graphics.Shapes;
+
+namespace osu.Game.Rulesets.Osu.Objects.Drawables.Pieces
+{
+    public class RingPiece : CircularContainer
+    {
+        public RingPiece()
+        {
+            Size = new Vector2(OsuHitObject.OBJECT_RADIUS * 2);
+
+            Anchor = Anchor.Centre;
+            Origin = Anchor.Centre;
+
+            Masking = true;
+            BorderThickness = 9; // roughly matches slider borders and makes stacked circles distinctly visible from each other.
+            BorderColour = Color4.White;
+
+            Child = new Box
+            {
+                AlwaysPresent = true,
+                Alpha = 0,
+                RelativeSizeAxes = Axes.Both
+            };
+        }
+    }
+}