diff --git a/GTP/.game.py.swp b/GTP/.game.py.swp
deleted file mode 100644
index 4ad0ba6..0000000
Binary files a/GTP/.game.py.swp and /dev/null differ
diff --git a/GTP/.test.py.swp b/GTP/.test.py.swp
index 71ca4b4..b635af1 100644
Binary files a/GTP/.test.py.swp and b/GTP/.test.py.swp differ
diff --git a/GTP/game.py b/GTP/game.py
index c5d58fa..7f1b4c6 100644
--- a/GTP/game.py
+++ b/GTP/game.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # vim:fenc=utf-8
 # $File: game.py
-# $Date: Tue Nov 28 01:1540 2017 +0800
+# $Date: Tue Nov 28 14:4726 2017 +0800
 # $Author: renyong15 © <mails.tsinghua.edu.cn>
 #
 
@@ -43,8 +43,43 @@ class Executor:
         return True,block
 
 
-    def _check_qi(self, vertex):
-        pass
+    def _is_qi(self, color, vertex):
+        nei = self._neighbor(vertex)
+        for n in nei:
+            if self.game.board[self.game._flatten(n)] == utils.EMPTY:
+                return True
+         
+        self.game.board[self.game._flatten(vertex)] = color
+        for n in nei:
+            if self.game.board[self.game._flatten(n)] == utils.another_color(color):
+                can_kill,block = self._find_block(n)
+                if can_kill: 
+                    self.game.board[self.game._flatten(vertex)] = utils.EMPTY
+                    return True
+
+        ### can not suicide
+        can_kill,block = self._find_block(vertex)
+        if can_kill: 
+            self.game.board[self.game._flatten(vertex)] = utils.EMPTY
+            return False
+
+        self.game.board[self.game._flatten(vertex)] = utils.EMPTY
+        return True
+
+
+    def _check_global_isomorphous(self, color, vertex):
+        ##backup
+        _board = copy.copy(self.game.board)
+        self.game.board[self.game._flatten(vertex)] = color
+        self._process_board(color, vertex)
+        if self.game.board in self.game.history:
+            res = True
+        else:
+            res = False
+
+        self.game.board = _board
+        return res
+
 
     def _in_board(self, vertex):
         x, y =  vertex
@@ -74,16 +109,30 @@ class Executor:
                         
 
     def is_valid(self, color, vertex):
+        ### in board
         if not self._in_board(vertex):
             return False
+
+        ### already have stone
+        if not self.game.board[self.game._flatten(vertex)] == utils.EMPTY:
+            return False
+
+        ### check if it is qi
+        if not self._is_qi(color, vertex):
+            return False
+
+
+        if self._check_global_isomorphous(color, vertex):
+            return False
+
         return True
 
     def do_move(self, color, vertex):
         if not self.is_valid(color, vertex):
             return False
-        self.game.history.append(copy.copy(self.game.board))
         self.game.board[self.game._flatten(vertex)] = color
         self._process_board(color,vertex)
+        self.game.history.append(copy.copy(self.game.board))
         return True
 
 
diff --git a/GTP/test.py b/GTP/test.py
index 0574ce0..0b8d4df 100644
--- a/GTP/test.py
+++ b/GTP/test.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # vim:fenc=utf-8
 # $File: test.py
-# $Date: Tue Nov 28 01:0627 2017 +0800
+# $Date: Tue Nov 28 14:4717 2017 +0800
 # $Author: renyong15 © <mails.tsinghua.edu.cn>
 #
 
@@ -44,11 +44,11 @@ print(res)
 res = e.run_cmd('8 genmove BLACK')
 print(res)
 
-g.show_board()
+#g.show_board()
 print(g.check_valid((10, 9)))
 print(g.executor._neighbor((1,1)))
 print(g.do_move(utils.WHITE, (4, 6)))
-g.show_board()
+#g.show_board()
 
 
 res = e.run_cmd('play BLACK L10')
@@ -88,7 +88,7 @@ print(res)
 
 res = e.run_cmd('play BLACK N12')
 print(res)
-g.show_board()
+#g.show_board()
 
 res = e.run_cmd('play BLACK P16')
 res = e.run_cmd('play BLACK P17')
@@ -97,7 +97,6 @@ res = e.run_cmd('play BLACK P19')
 res = e.run_cmd('play BLACK Q16')
 res = e.run_cmd('play BLACK R16')
 res = e.run_cmd('play BLACK S16')
-res = e.run_cmd('play BLACK S19')
 
 res = e.run_cmd('play WHITE S18')
 res = e.run_cmd('play WHITE S17')
@@ -106,12 +105,37 @@ res = e.run_cmd('play WHITE Q18')
 res = e.run_cmd('play WHITE Q17')
 res = e.run_cmd('play WHITE R18')
 res = e.run_cmd('play WHITE R17')
+res = e.run_cmd('play BLACK S19')
 print(res)
-g.show_board()
+#g.show_board()
 
 res = e.run_cmd('play WHITE R19')
 g.show_board()
 
 res = e.run_cmd('play BLACK S19')
+print(res)
 g.show_board()
 
+res = e.run_cmd('play BLACK S19')
+print(res)
+
+
+res = e.run_cmd('play BLACK E17')
+res = e.run_cmd('play BLACK F16')
+res = e.run_cmd('play BLACK F18')
+res = e.run_cmd('play BLACK G17')
+res = e.run_cmd('play WHITE G16')
+res = e.run_cmd('play WHITE G18')
+res = e.run_cmd('play WHITE H17')
+g.show_board()
+
+res = e.run_cmd('play WHITE F17')
+g.show_board()
+
+res = e.run_cmd('play BLACK G17')
+print(res)
+g.show_board()
+
+res = e.run_cmd('play BLACK G19')
+res = e.run_cmd('play BLACK G17')
+g.show_board()