Add basic implementation of particle explosion

Using drawables still, just to get things in place and setup the
structure

osu.Game.Tests/Visual/Gameplay/TestSceneParticleExplosion.cs

@@ -0,0 +1,30 @@
+// 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 NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Textures;
+using osu.Game.Graphics;
+using osuTK;
+
+namespace osu.Game.Tests.Visual.Gameplay
+{
+    [TestFixture]
+    public class TestSceneParticleExplosion : OsuTestScene
+    {
+        [BackgroundDependencyLoader]
+        private void load(TextureStore textures)
+        {
+            AddStep(@"display", () =>
+            {
+                Child = new ParticleExplosion(textures.Get("Cursor/cursortrail"), 150, 1200)
+                {
+                    Anchor = Anchor.Centre,
+                    Origin = Anchor.Centre,
+                    Size = new Vector2(200)
+                };
+            });
+        }
+    }
+}

osu.Game/Graphics/ParticleExplosion.cs

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+// 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 System;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Graphics.Textures;
+using osu.Framework.Utils;
+using osuTK;
+
+namespace osu.Game.Graphics
+{
+    public class ParticleExplosion : CompositeDrawable
+    {
+        public ParticleExplosion(Texture texture, int particleCount, double duration)
+        {
+            for (int i = 0; i < particleCount; i++)
+            {
+                double rDuration = RNG.NextDouble(duration / 3, duration);
+
+                AddInternal(new Particle(rDuration, RNG.NextSingle(0, MathF.PI * 2))
+                {
+                    Texture = texture
+                });
+            }
+        }
+
+        private class Particle : Sprite
+        {
+            private readonly double duration;
+            private readonly float direction;
+
+            private Vector2 positionForOffset(float offset) => new Vector2(
+                (float)(offset * Math.Sin(direction)),
+                (float)(offset * Math.Cos(direction))
+            );
+
+            public Particle(double duration, float direction)
+            {
+                this.duration = duration;
+                this.direction = direction;
+                Anchor = Anchor.Centre;
+                Origin = Anchor.Centre;
+                RelativePositionAxes = Axes.Both;
+                Position = positionForOffset(0);
+            }
+
+            protected override void LoadComplete()
+            {
+                base.LoadComplete();
+
+                this.MoveTo(positionForOffset(1), duration);
+                this.FadeOut(duration);
+                Expire();
+            }
+        }
+    }
+}