import random


grid = [
    [0, 2, 0, 4],
    [0, 0, 8, 0],
    [2, 0, 0, 2],
    [0, 0, 0, 2]
]


def print_grid(grid):
    for row in grid:
        print(" | ".join(str(cell) for cell in row))
    print("-" * 15)

def get_move():
    while True:
        move = input("Move (w/a/s/d): ")
        if move in ["w", "a", "s", "d"]:
            return move
        print("Invalid! Use w, a, s, or d.")

def slide_merge(line):
    new_line = [x for x in line if x != 0]
    for i in range(len(new_line) - 1):
        if new_line[i] == new_line[i + 1]:
            new_line[i] = new_line[i] * 2
            new_line[i + 1] = 0
    new_line = [x for x in new_line if x != 0]
    new_line += [0] * (4 - len(new_line))
    return new_line

def move_up(grid):
    for col in range(4):
        column = [grid[row][col] for row in range(4)]
        new_column = slide_merge(column)
        for row in range(4):
            grid[row][col] = new_column[row]

def move_down(grid):
    for col in range(4):
        column = [grid[row][col] for row in range(4)]
        new_column = slide_merge(column[::-1])[::-1]
        for row in range(4):
            grid[row][col] = new_column[row]

def move_left(grid):
    for row in range(4):
        grid[row] = slide_merge(grid[row])

def move_right(grid):
    for row in range(4):
        grid[row] = slide_merge(grid[row][::-1])[::-1]

def check_win(grid):
    for row in grid:
        for cell in row:
            if cell == 2048:
                return True
    return False

def check_game_over(grid):
    for row in grid:
        for cell in row:
            if cell == 0:
                return False

    for row in grid:
        for i in range(3):
            if row[i] == row[i + 1]:
                return False

    for col in range(4):
        for row in range(3):
            if grid[row][col] == grid[row + 1][col]:
                return False

    return True

def add_random_tile(grid):
    empty_cells = []
    for row in range(4):
        for col in range(4):
            if grid[row][col] == 0:
                empty_cells.append((row, col))

    if len(empty_cells) == 0:
        return

    row, col = random.choice(empty_cells)
    grid[row][col] = 2 if random.random() < 0.9 else 4

print_grid(grid)

while True:
    direction = get_move()
    if direction == "w":
        move_up(grid)
    elif direction == "s":
        move_down(grid)
    elif direction == "a":
        move_left(grid)
    elif direction == "d":
        move_right(grid)
    add_random_tile(grid)
    print_grid(grid)

    if check_win(grid):
        print("You win!")
        break
    if check_game_over(grid):
        print("Game over!")
        break