homing weapons more or less work now

OpenRa.Game/Effects/Smoke.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using OpenRa.Game.Graphics;
+
+namespace OpenRa.Game.Effects
+{
+	class Smoke : IEffect
+	{
+		readonly int2 pos;
+		readonly Animation anim = new Animation("smokey");
+
+		public Smoke(int2 pos)
+		{
+			this.pos = pos;
+			anim.PlayThen("idle",
+				() => Game.world.AddFrameEndTask(
+					w => w.Remove(this)));
+		}
+
+		public void Tick()
+		{
+			anim.Tick();
+		}
+
+		public IEnumerable<Tuple<Sprite, float2, int>> Render()
+		{
+			yield return Tuple.New(anim.Image, pos.ToFloat2() - .5f * anim.Image.size, 0);
+		}
+	}
+}