diff --git a/src/go/core.py b/src/go/core.py
--- a/src/go/core.py
+++ b/src/go/core.py
@@ -1,6 +1,7 @@
 import logging as log
 
 from util import EMPTY,BLACK,WHITE,colorNames
+from .helperboard import HelperBoard
 from .gamerecord import GameRecord
 
 
@@ -9,10 +10,13 @@ class Go:
 	def __init__(self,boardSize=19):
 		self.boardSize=boardSize
 		self.board=[[EMPTY]*boardSize for x in range(boardSize)]
-		self._temp=[[EMPTY]*boardSize for x in range(boardSize)]
 		self.toMove=BLACK
+		self._helper=HelperBoard(self.board)
 		self._record=GameRecord()
 
+	def listMoves(self,diff=[]):
+		return []
+
 	## Executes a move.
 	#
 	#  Doesn't check for kos. Suicide not allowed.
@@ -27,48 +31,39 @@ class Go:
 
 		# capture neighbors
 		for r,c in ((-1,0),(1,0),(0,-1),(0,1)):
-			self._clearTemp()
-			if not self._floodFill(-color,row+r,col+c): self._remove()
+			self._helper.clear()
+			if not self._helper.floodFill(-color,row+r,col+c,EMPTY): self._remove()
 
 		# check for suicide
-		self._clearTemp()
-		if not self._floodFill(color,row,col):
+		self._helper.clear()
+		if not self._helper.floodFill(color,row,col,EMPTY):
 			self.board[row][col]=EMPTY
 			return False
 		self._record.move(color,row,col)
 		self.toMove=-1*color
 		return True
 
+	def undoMove(self,color,r,c,captures):
+		self.board[r][c]=color
+		if len(captures)>0:
+			self._helper.clear()
+			for (r,c) in captures:
+				self._helper.floodFill(EMPTY,r,c)
+			self._fill(-color)
+
 	def transitionMove(self,board):
 		res=transitionMove(self.board,board)
 		if not res: return res
 		(r,c,color)=res
 		return self.move(color,r,c)
 
+	## Removes stones at coordinates marked with True in self.helper.
+	def _remove(self):
+		self._fill(EMPTY)
 
-	## Checks for liberties of a stone at given coordinates.
-	#
-	#  The stone's group is marked with True in self.temp, ready for capture if needed. Recursively called for stone's neighbors.
-	#
-	#  @return True if alive, False if captured
-	def _floodFill(self,color,row,col):
-		if col<0 or col>=self.boardSize or row<0 or row>=self.boardSize: return False # out of range
-		if self._temp[row][col]: return False # already visited
-		if self.board[row][col]==EMPTY: return True # found a liberty
-		if self.board[row][col]!=color: return False # opponent's stone
-		self._temp[row][col]=True # set visited
-		return self._floodFill(color,row,col-1) or self._floodFill(color,row,col+1) or self._floodFill(color,row-1,col) or self._floodFill(color,row+1,col) # check neighbors
-
-	## Removes stones at coordinates marked with True in self.temp.
-	def _remove(self):
-		for r in range(self.boardSize):
-			for c in range(self.boardSize):
-				if self._temp[r][c]: self.board[r][c]=EMPTY
-
-	def _clearTemp(self):
-		for i in range(self.boardSize):
-			for j in range(self.boardSize):
-				self._temp[i][j]=EMPTY
+	def _fill(self,filling):
+		for (r,c) in self._helper.continuousArea():
+			self.board[r][c]=filling
 
 
 def exportBoard(board):
@@ -106,7 +101,7 @@ def transitionMove(state1,state2):
 		return False
 
 
-def transitionSequence(state1,state2,diff):
+def transitionSequence(state1,state2,diff,limit=0):
 	return []