Rename shadow tween extension methods

Author: adamgraham

Runtime/Extensions/UI/ShadowTweens.cs

@@ -5,12 +5,17 @@ namespace Zigurous.Tweening
 {
     public static class ShadowTweens
     {
-        public static Tween TweenEffectColor(this Shadow shadow, Color to, float duration) =>
+        public static Tween TweenColor(this Shadow shadow, Color to, float duration) =>
             Tweening.To(getter: () => shadow.effectColor,
                         setter: effectColor => shadow.effectColor = effectColor,
                         to, duration).SetTarget(shadow);
 
-        public static Tween TweenEffectDistance(this Shadow shadow, Vector2 to, float duration) =>
+        public static Tween TweenAlpha(this Shadow shadow, float to, float duration) =>
+            Tweening.To(getter: () => shadow.effectColor.a,
+                        setter: alpha => shadow.effectColor = new Color(shadow.effectColor.r, shadow.effectColor.g, shadow.effectColor.b, alpha),
+                        to, duration).SetTarget(shadow);
+
+        public static Tween TweenDistance(this Shadow shadow, Vector2 to, float duration) =>
             Tweening.To(getter: () => shadow.effectDistance,
                         setter: effectDistance => shadow.effectDistance = effectDistance,
                         to, duration).SetTarget(shadow);