Add "at anchor" skin selector.

Assets/Cryville/Crtr/SkinInterpreter.cs

@@ -28,7 +28,7 @@ namespace Cryville.Crtr {
 						GetChar();
 						if (cc == '.') {
 							GetChar();
-							s.Add(new SkinSelector.State(GetIdentifier()));
+							s.Add(new SkinSelector.AtAnchor(GetIdentifier()));
 							key = null;
 						}
 						else {

Assets/Cryville/Crtr/SkinSelectors.cs

@@ -104,6 +104,23 @@ namespace Cryville.Crtr {
 				return h.Handler.Anchors[Name].Opened;
 			}
 		}
+		public class AtAnchor : SkinSelector {
+			public int Name { get; private set; }
+			public AtAnchor(string name) {
+				Name = IdentifierManager.SharedInstance.Request(name);
+			}
+			public override bool IsStatic {
+				get { return false; }
+			}
+
+			public override Transform Match(ContainerState h, Transform a, bool dyn = false) {
+				if (!dyn) throw new SelectorNotStaticException();
+				return IsUpdatable(h) ? a : null;
+			}
+			public override bool IsUpdatable(ContainerState h) {
+				return h.Handler.Anchors[Name].Opened;
+			}
+		}
 		public class Property : SkinSelector {
 			readonly PdtExpression _exp;
 			readonly PdtOperator _op;