code: private int rational(int n) {
  		while (n >= shapes.size()) {
  			n -= shapes.size();
  		}
  		while (n < 0) {
  			n += shapes.size();
  		}
  		
  		return n;
  	}
docs: Get an index that is rational, i.e. fits inside this set of shapes
  
  @param n The index to rationalize
  @return The index rationalized