I've been building upon the dungeon game these past few days, and i've hit a roadblock. Any ideas?

import os
import random

#Display Monster
#Let the monster move too



CELLS = [(0, 0), (1, 0), (2, 0), (3, 0), (4, 0),
         (0, 1), (1, 1), (2, 1), (3, 1), (4, 1),
         (0, 2), (1, 2), (2, 2), (3, 2), (4, 2),
         (0, 3), (1, 3), (2, 3), (3, 3), (4, 3),
         (0, 4), (1, 4), (2, 4), (3, 4), (4, 4)]

MONSTER_MOVE = (1,2,3,4,5,6,7,8)

def clear_screen():
    os.system('cls' if os.name == 'nt' else 'clear')


def get_locations():                    # pick random location for player
    return random.sample(CELLS, 3)      # pick random location for the monster
                                        # pick random location for exit door



def move_player(player, move):          # move player
    x, y = player
    if move == "W":
        x -= 1
    if move == "E":
        x += 1
    if move == "N":
        y -= 1
    if move == "S":
        y += 1
    if move == "NW":                    #Allow diagonal movement
        x -= 1
        y -= 1
    if move == "NE":
        x += 1
        y -= 1
    if move == "SW":
        x -= 1
        y += 1
    if move == "SE":
        x += 1
        y += 1
    return x, y


def get_moves(player):                             
    moves = ["W", "E", "N", "S", "NW", "NE", "SW", "SE"]         # take input for movement
    x, y = player
    if x == 4 and y == 4:
        moves.remove("S")
        moves.remove("SE")
        moves.remove("SW")
        moves.remove("E")
        moves.remove("NE")
    if x == 4 and y == 0:
        moves.remove("N")
        moves.remove("NW")
        moves.remove("NE")
        moves.remove("E")
        moves.remove("SE")
    if x == 0 and y == 4:
        moves.remove("W")
        moves.remove("NW")
        moves.remove("S")
        moves.remove("SW")
        moves.remove("SE")
    if x == 0 and y == 0:
        moves.remove("W")
        moves.remove("NW")
        moves.remove("NE")
        moves.remove("N")
        moves.remove("SW")
    if x == 0:                                                   # invalid moves (past edges of grid)
        moves.remove("W")
        moves.remove("NW")
        moves.remove("SW")
    if x == 4:
        moves.remove("NE")
        moves.remove("SE")
        moves.remove("E")
    if y == 0:
        moves.remove("NW")
        moves.remove("NE")
        moves.remove("N")
    if y == 4:
        moves.remove("S")
        moves.remove("SE")
        moves.remove("SW")
    return moves


#def monster_wander(monster):

def draw_map(player):           # draw grid

    print(" _"*5)
    tile = "|{}"

    for cell in CELLS:
        x, y = cell
        if x < 4:
            line_end = ""
            if cell == player:              # draw player in the grid
                output = tile.format("X")
            else:
                output = tile.format("_")
        else:
            line_end = "\n"
            if cell == player:
                output = tile.format("X|")
            else:
                output = tile.format("_|")
        print(output, end=line_end)


def game_loop():
    monster, door, player = get_locations()
    playing = True

    while playing:
        clear_screen()                       # clear screen and redraw grid
        draw_map(player)
        valid_moves = get_moves(player)

        print("You're currently in room {}".format(player))
        print("You can move {}".format(", ".join(valid_moves)))
        print("Enter QUIT to quit")

        move = input("> ")
        move = move.upper()

        if move == 'QUIT':
            print("\n ** See you next time! **\n")
            break
        if move in valid_moves:
            player = move_player(player, move)

            if player == monster:                                                       # check for win/loss
                print("\n ** Oh no! The monster got you! Better luck next time! **\n")
                playing = False
            if player == door:
                print("\n ** You escaped! Congratulations! **\n")
                playing = False
        else:
            input("\n ** Walls are hard! Don't run into them! **\n")
    else:
        if input("Play again? [Y/N] ").lower() != "n":
            game_loop()


clear_screen()
print("Welcome to the dungeon!")
input("Press return to start!")
clear_screen()
game_loop()