import math
import random
  
class Point:
  
    def __init__(self, row, col):
        self.row = row
        self.col = col
    
    def __eq__(self, other):
        return self.row == other.row and self.col == other.col
  
  
class Snake:
  
    def __init__(self, point):
        self._points = [point]
        self._head = point
        self._direction = random.uniform() * math.pi
  
    def has_point(self, point):
        for p in self._points:
            if p == point:
                return True
        return False
  
    def grow(self):
        pass
  
    def move(self, point):
        self._points.pop()  # remove tail
        self._points.insert(0, point)  # move head
        self._head = point
  
    def nex_position(self):
        pass
  
    def bounce(self):
        pass
      
       
class Game:
  
    def __init__(self):
        self._snakes = []
  
    def _collision(self, point):
        for snake in self._snakes:
            if snake.has_point(point):
                return True
        return False
  
    def add_snake(self, point):
        if self._collision(point):
            raise Exception("Point has already owned by snake")
        self._snakes.append(Snake(point))
  
    def loop(self):
        while True:
            for snake in self._snakes:
                nex_position = snake.nex_position()
                if self._collision(nex_position):
                    snake.bounce()
                else:
                    snake.move(nex_position)