add wind up and wind down mods

osu.Game/Rulesets/Mods/ModWindUp.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using osu.Framework.Audio;
+using osu.Framework.Audio.Track;
+using osu.Framework.Configuration;
+using osu.Framework.Timing;
+using osu.Framework.Graphics;
+using osu.Game.Beatmaps;
+using osu.Game.Graphics;
+using osu.Game.Rulesets.UI;
+using osu.Game.Rulesets.Objects;
+
+namespace osu.Game.Rulesets.Mods
+{
+    public abstract class ModWindUp : Mod
+    {
+        public override string Name => "Wind Up";
+        public override string Acronym => "WU";
+        public override ModType Type => ModType.Fun;
+        public override FontAwesome Icon => FontAwesome.fa_chevron_circle_up;
+        public override string Description => "Crank it up!";
+        public override double ScoreMultiplier => 1;
+        public override Type[] IncompatibleMods => new[] { typeof(ModDoubleTime), typeof(ModHalfTime) };
+        public abstract double AppendRate { get; }
+    }
+
+    public class ModWindUp<T> : ModWindUp, IUpdatableByPlayfield, IApplicableToClock, IApplicableToRulesetContainer<T>
+        where T : HitObject
+    {
+        private Track Track;
+        private IAdjustableClock Clock;
+        private IHasPitchAdjust ClockAdjust;
+        public override double AppendRate => 0.5;
+
+        public virtual void ApplyToClock(IAdjustableClock clock)
+        {
+            Clock = clock;
+            ClockAdjust = clock as IHasPitchAdjust;
+        }
+
+        public virtual void ApplyToRulesetContainer(RulesetContainer<T> ruleset)
+        {
+            Track = ruleset.WorkingBeatmap.Track;
+        }
+
+        public virtual void Update(Playfield playfield)
+        {
+            double newRate = 1 + (AppendRate * (Track.CurrentTime / Track.Length));
+            Clock.Rate = newRate;
+            ClockAdjust.PitchAdjust = newRate;
+        }
+    }
+}