from dataclasses import dataclass
from typing import List, Optional

@dataclass
class Cell:
    x: int
    y: int
    is_wall: bool = False
    is_start: bool = False
    is_exit: bool = False

    def is_passable(self) -> bool:
        return not self.is_wall

class Maze:
    def __init__(self, width: int, height: int):
        self.width = width
        self.height = height
        self.cells = [[Cell(x, y) for x in range(width)] for y in range(height)]
        self.start: Optional[Cell] = None
        self.exit: Optional[Cell] = None

    def get_cell(self, x: int, y: int) -> Optional[Cell]:
        if 0 <= x < self.width and 0 <= y < self.height:
            return self.cells[y][x]
        return None

    def get_neighbors(self, cell: Cell) -> List[Cell]:
        neighbors = []
        for dx, dy in ((0,1), (0,-1), (1,0), (-1,0)):
            nx, ny = cell.x + dx, cell.y + dy
            neighbor = self.get_cell(nx, ny)
            if neighbor and neighbor.is_passable():
                neighbors.append(neighbor)
        return neighbors