import Vec

class Snake:

    cells = []
    heading = Vec.up

    def __init__(self, cells):
        self.cells = cells

    def move(self):
        self.cells.pop()
        self.cells.insert(0, self.cells[0] + self.heading)

    def headInTail(self):
        res = False
        for i in range(1, len(self.cells)):
            res = res or (self.cells[0] == self.cells[i])
        return res

    def head(self):
        return self.cells[0]