我无法弄清楚我的代码有什么问题

这个想法是模拟池塘中的生活。问题出在类方法reproduction(self)中。给出“列表索引超出范围”，我该如何正常修复它？

import pygame
from pygame import *
import random

stone_count = 50;
seawed_count = 50;
width,height = 100, 50;
directions = [
    [-1,0],
    [1,0],
    [0,1],
    [0,-1],
    [-1,1],
    [-1,-1],
    [1,-1],
    [1,1],
    [0,0],
    ]

def derictionRandomazer(arr):
    random.shuffle(arr)
    # print(arr);
    return arr

# def is_suitable(arr):
#     print(arr);


pygame.init()

screen = pygame.display.set_mode( (width * 10, height * 10) )
pygame.display.set_caption("Life in Pond"); 
class Place:
    color = (52,152,219)
    def __init__(self, x,y):
        self.x = x
        self.y = y 

    def aseta(self):
        square = pygame.Rect(self.x*10, self.y*10, 10, 10)
        pygame.draw.rect(screen, self.color, square)

class Stone(Place):
    color = (0,0,0)

class Seaweed(Place):
    lifePeriod = 20;
    color = (2,124,2)
    reproductivePeriod = 5;
    def __init__(self,x,y):
        super().__init__(x,y)
        self.age = 0;

    def aging(self):
        self.age += 1;
        if self.age == self.lifePeriod:
            self.dying();
        elif self.age % self.reproductivePeriod == 0:
            self.reproduction();
    
    def reproduction(self):
        for direction in derictionRandomazer(directions):
            new_x = self.x + direction[0];
            new_y = self.y + direction[1];
            if type(pond[new_x][new_y]) == Place:
                pond[new_x][new_y] = Seaweed(new_x,new_y)
                pond[new_x][new_y].aseta();

    def dying(self):
        pond[self.x][self.y] = Place(self.x, self.y)
        pond[self.x][self.y].aseta();

pond = [[ 0 for x in range(width)] for y in range(width)]

# заполнили массив обьектами Place
for y in range(height):
    for x in range(width):
        pond[x][y] = Place(x,y);
        pond[x][y].aseta();

pygame.display.flip();

num = 0

# Добавляем Stone
while num <= stone_count:
    x = random.randint(1,width-2)
    y = random.randint(1,height-2)
    if type(pond[x][y]) == Place:
        pond[x][y] = Stone(x,y)
        pond[x][y].aseta();
        num += 1


pygame.display.flip();

seawedNum = 0

# Добавляем Seaweeds
while seawedNum <= seawed_count:
    x = random.randint(1,width-2)
    y = random.randint(1,height-2)
    if type(pond[x][y]) == Place:
        pond[x][y] = Seaweed(x,y)
        pond[x][y].aseta();
        seawedNum += 1

pygame.display.flip();
s = 0
while True:

    for y in range(height):
        for x in range(width):
            if type(pond[x][y]) == Seaweed:
                s+=1
                # print(s)
                pond[x][y].aging();
    pygame.display.flip();