diff --git a/src/go/helperboard.py b/src/go/helperboard.py
--- a/src/go/helperboard.py
+++ b/src/go/helperboard.py
@@ -13,6 +13,9 @@ class HelperBoard:
 		self._libs=[0]*(self._boardSize**2)*2
 		self._libCount=0
 
+	## Performs a recursive breadth first search of a continuous area filled with filling.
+	#
+	# @return {True,False}: True on encountering needle (usually free liberty), False otherwise.
 	def floodFill(self,filling,r,c,needle=None):
 		if c<0 or c>=self._boardSize or r<0 or r>=self._boardSize: return False # out of range
 		if self._board[r][c]: return False # already visited