Moving the Whole Board

import random
# ===== Working functions from previous lessons =====
def add_random_tile(board: list[list[int]]) -> None:
    empty_positions = [
        (r, c)
        for r in range(4)
        for c in range(4)
        if board[r][c] == 0
    ]
    if not empty_positions:
        return
    r, c = random.choice(empty_positions)
    board[r][c] = 4 if random.random() < 0.1 else 2
def create_initial_board() -> list[list[int]]:
    board = [[0] * 4 for _ in range(4)]
    add_random_tile(board)
    add_random_tile(board)
    return board
def render_board(board: list[list[int]]) -> str:
    size = len(board)
    cell_width = 5
    line = "+" + ("-" * cell_width + "+") * size
    lines = [line]
    for r in range(size):
        row_text = "|"
        for c in range(size):
            val = board[r][c]
            text = "" if val == 0 else str(val)
            row_text += text.rjust(cell_width) + "|"
        lines.append(row_text)
        lines.append(line)
    return "\n".join(lines)
def compress_row(row: list[int]) -> list[int]:
    non_zero = [x for x in row if x != 0]
    zeros_needed = len(row) - len(non_zero)
    return non_zero + [0] * zeros_needed
def merge_row(row: list[int]) -> tuple[list[int], int]:
    result = []
    score = 0
    i = 0
    n = len(row)
    while i < n:
        if row[i] == 0:
            break
        if i + 1 < n and row[i] == row[i + 1] and row[i] != 0:
            merged = 2 * row[i]
            result.append(merged)
            score += merged
            i += 2
        else:
            result.append(row[i])
            i += 1
    while len(result) < n:
        result.append(0)
    return result, score
def move_left(board: list[list[int]]) -> tuple[list[list[int]], int, bool]:
    total_score = 0
    changed = False
    new_board = []
    for row in board:
        new_row, gained = compress_merge_row(row)
        total_score += gained
        if new_row != row:
            changed = True
        new_board.append(new_row)
    return new_board, total_score, changed
# ===== Lesson 6: helper + target functions =====
def transpose(board: list[list[int]]) -> list[list[int]]:
    """
    Return the transpose of the 4x4 board (rows <-> columns).
    We'll implement this in this lesson.
    """
    # TODO
    raise NotImplementedError
def reverse_rows(board: list[list[int]]) -> list[list[int]]:
    """
    Return a new board where each row is reversed (for left/right moves).
    We'll implement this in this lesson.
    """
    # TODO
    raise NotImplementedError
def move_board(board: list[list[int]], direction: str) -> tuple[list[list[int]], int, bool]:
    """
    Apply a move to the board in one of the four directions:
    'left', 'right', 'up', 'down'.
    Returns:
        new_board: the updated 4x4 board
        gained_score: total score from merged tiles
        moved: True if the board actually changed, else False
    """
    # TODO: implement in this lesson
    raise NotImplementedError
# ===== Still stubbed; will be done in Lesson 7+ =====
def check_game_state(board: list[list[int]], target: int = 2048) -> str:
    raise NotImplementedError
def main():
    board = create_initial_board()
    score = 0
    print("Initial board:")
    print("Score:", score)
    print(render_board(board))
    # We'll add interactive moves here later in the lesson.
if __name__ == "__main__":
    main()