Add "transform" mod

osu.Game.Rulesets.Osu/Mods/OsuModTransform.cs

@@ -0,0 +1,51 @@
+// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using System.Collections.Generic;
+using osu.Framework.Graphics;
+using osu.Game.Graphics;
+using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.Objects.Drawables;
+using osu.Game.Rulesets.Osu.Objects;
+using OpenTK;
+
+namespace osu.Game.Rulesets.Osu.Mods
+{
+    internal class OsuModTransform : Mod, IApplicableToDrawableHitObjects
+    {
+        public override string Name => "Transform";
+        public override string ShortenedName => "TR";
+        public override FontAwesome Icon => FontAwesome.fa_arrows;
+        public override ModType Type => ModType.Fun;
+        public override string Description => "Everything rotates. EVERYTHING.";
+        public override double ScoreMultiplier => 1;
+        private float theta;
+
+        public void ApplyToDrawableHitObjects(IEnumerable<DrawableHitObject> drawables)
+        {
+            foreach (var drawable in drawables)
+            {
+                var hitObject = (OsuHitObject) drawable.HitObject;
+
+                float appearDistance = (float)(hitObject.TimePreempt - hitObject.TimeFadeIn) / 2;
+
+                Vector2 originalPosition = drawable.Position;
+                Vector2 appearOffset = new Vector2((float)Math.Cos(theta), (float)Math.Sin(theta)) * appearDistance;
+
+                //the - 1 and + 1 prevents the hit objects to appear in the wrong position.
+                double appearTime = hitObject.StartTime - hitObject.TimePreempt - 1;
+                double moveDuration = hitObject.TimePreempt + 1;
+
+                using (drawable.BeginAbsoluteSequence(appearTime, true))
+                {
+                    drawable
+                        .MoveToOffset(appearOffset)
+                        .MoveTo(originalPosition, moveDuration, Easing.InOutSine);
+                }
+
+                theta += (float) hitObject.TimeFadeIn / 1000;
+            }
+        }
+    }
+}

osu.Game.Rulesets.Osu/OsuRuleset.cs

@@ -118,8 +118,8 @@ public override IEnumerable<Mod> GetModsFor(ModType type)
                         new OsuModAutopilot(),
                     };
                 case ModType.Fun:
-                    return new Mod[]
-                    {
+                    return new Mod[] {
+                        new OsuModTransform(),
                         new OsuModWiggle(),
                     };
                 default: