diff --git a/src/statebag.py b/src/statebag/__init__.py
copy from src/statebag.py
copy to src/statebag/__init__.py
--- a/src/statebag.py
+++ b/src/statebag/__init__.py
@@ -16,19 +16,7 @@ So we try to find the correct crossover 
 	- remember the better variant
 - linearize the fork back by discarding s'_j-s preceding the crossover and s_j-s following the crossover
 """
-from util import EMPTY,BLACK,WHITE, hashBoard,exportBoard
-from go.engine import getTransitionSequence
-
-
-## Crude lower bound on edit distance between states.
-def estimateDistance(diff):
-	# lot of room for improvements
-	additions=sum(1 for d in diff if d[2]=="+")
-	deletions=sum(1 for d in diff if d[2]=="-")
-	replacements=len(diff)-additions-deletions
-	if additions>0: return additions+replacements
-	elif replacements==0 and deletions>0: return 2 # take n, return 1
-	return replacements+1 # ???
+from .boardstate import BoardState
 
 
 ## Update contents of diff1 by contents of diff2.
@@ -65,81 +53,6 @@ def transformSingle(action1,item1,action
 	return None
 
 
-class GameTreeNode:
-	def __init__(self,parent,color):
-		self.parent=parent
-		self.color=color # color closing the move sequence
-		self.prev=None
-		self.moves=[] # move sequence from prev to self
-		self.weight=0
-
-	## Connect itself after v if it gains itself more weight.
-	def tryConnect(self,v,diff):
-		moves=getTransitionSequence(v.parent,self.parent,-1*v.color,self.color,diff)
-		if not moves: return
-		w=v.weight+2-len(moves) # proper one move transition increases the weight by 1
-		if w>self.weight:
-			self.moves=moves
-			self.prev=v
-			self.weight=w
-
-
-class BoardState:
-	def __init__(self,board):
-		self._board=tuple(tuple(x for x in row) for row in board)
-		self.nodes=(GameTreeNode(self,BLACK),GameTreeNode(self,WHITE))
-		self.cachedDiff=[]
-		self._hash=None
-
-	def tryConnect(self,s,diff=None):
-		if diff is None: diff=self-s
-		distEst=estimateDistance(diff)
-		if distEst>3: return # we couldn't find every such move sequence anyway without a clever algorithm
-		weightEst=s.getWeight()+2-distEst
-		if weightEst<=self.getWeight(): return
-		for v1 in s.nodes:
-			for v2 in self.nodes:
-				v2.tryConnect(v1,diff)
-
-	def hash(self):
-		if self._hash is None: self._hash=hashBoard(self._board)
-		return self._hash
-
-	def export(self):
-		return exportBoard(self._board)
-
-	def exportDiff(self,s2):
-		return "vvv\n{0}\n=== {1} ===\n{2}\n^^^".format(self.export(), s2-self, s2.export())
-
-	def __iter__(self): return iter(self._board)
-
-	def __getitem__(self,key): return self._board[key]
-
-	def __sub__(self,x):
-		res=[]
-
-		for (r,(row1,row2)) in enumerate(zip(self._board,x)):
-			for (c,(item1,item2)) in enumerate(zip(row1,row2)):
-				if item1==item2: continue
-				elif item2==EMPTY: res.append((r,c,"+",item1))
-				elif item1==EMPTY: res.append((r,c,"-",item2))
-				else: res.append((r,c,"*",item1)) # ->to
-		return res
-
-	def __eq__(self,x):
-		return self.hash()==x.hash()
-
-	def setWeight(self,val):
-		for v in self.nodes: v.weight=val
-
-	def getWeight(self):
-		return max(v.weight for v in self.nodes)
-
-	def getPrev(self):
-		v=max(self.nodes, key=lambda v: v.weight)
-		return v.prev.parent if v.prev else None
-
-
 class StateBag:
 	def __init__(self):
 		self._states=[]