code: static boolean isOpenEdge( SquareNode node , int index ) {
  		if( node.edges[index] == null )
  			return false;
  		int marker = node.edges[index].destination(node).graph;
  		return marker == SquareNode.RESET_GRAPH;
  	}
docs: Is the edge open and can be traversed to?  Can't be null and can't have
  the marker set to a none RESET_GRAPH value.