added async stone detection thread

field.py

@@ -5,7 +5,7 @@ from tetromino import Tetromino
 class Field():
 
     WIDTH = 20
-    HEIGHT = 10
+    HEIGHT = 20
 
     def __init__(self, state=None):
         if state:
@@ -52,6 +52,10 @@ class Field():
         self.state = [[' ' for cols in range(Field.WIDTH)]
                       for rows in range(Field.HEIGHT)]
 
+    def reset_half_field(self):
+        self.state = [[' ' for cols in range(Field.WIDTH)]
+                      for rows in range(int(Field.HEIGHT/2))]
+
     def rotate_state(self):
         self.state = self.rotate_90_degree_anticlckwise(self.state)
         #self.state = self.matrixflip(self.state, 'v')