为什么我的一些圈子消失了，而有些则没有？

游戏的重点是让所有圆圈在碰撞时消失，但由于某种原因，有些圆圈没有消失？- 提前谢谢你的帮助！

import turtle
import random
import math
import time

# Setting up the Screen
ms = turtle.Screen()
ms.bgcolor("red")
ms.title("Space Rocket Minigame @Rafa94")

# Using class functions/Methods

# subclass
class Border(turtle.Turtle):
    def __init__(self):  # class constrcutor
        turtle.Turtle.__init__(self)  # adding our Objects attributes all starting with "self"
        self.penup()
        self.hideturtle()
        self.speed(0)
        self.color("silver")
        self.pensize(5)

    def draw_border(self):
        self.penup()# getting our pen to start drawing
        self.goto(-300, -300)
        self.pendown()
        self.goto(-300, 300)
        self.goto(300, 300)
        self.goto(300, -300)
        self.goto(-300, -300)

class Player(turtle.Turtle):  # since it got inherited this class becomes a Superclass

    def __init__(self):  # self is our only argument here but it will have multiple attributes
        turtle.Turtle.__init__(self)  # since we are using the Turtle module, we are able to use it's built in functions
        self.penup()# our attributes
        self.speed(0)
        self.shape("triangle")
        self.color("black")
        self.velocity = 0.1

    def move(self):
        self.forward(self.velocity)

        # Border Checking
        if self.xcor() > 290 or self.xcor() < -290:  # Left side is -290 Right side is 290 we also want the coordinates x and y to be below 300 to not go over our border
            self.left(60)
        if self.ycor() > 290 or self.ycor() < -290:
            self.left(60)

    def turnleft(self):
        self.left(30)

    def turnright(self):
        self.right(30)

    def increasespeed(self):
        self.velocity += 1

class Goal(turtle.Turtle):  # Sub Class

    def __init__(self):
        # since we are using the Turtle module we are able to use it's built in functions
        turtle.Turtle.__init__(self)
        self.penup()  # our attributes
        self.speed(0)
        self.shape("circle")
        self.color("green")
        self.velocity = 3  #xcor                    #ycor
        self.goto(random.randint(-250, 250), random.randint(-250, 250))  # we are making our turtle "go to" X & Y coordinates by -250 and 250 only randomly. We also have our random module here aswell
        self.setheading(random.randint(0, 360))  # setting the heading to see in which direction i want it to go

    def jump(self):  # Jump = Collidee
        self.goto(random.randint(-250, 250), random.randint(-250, 250))  # "jump" stands for Collidee so if the circle "jumps" with player it will move to random postion by 250 and -25
        self.setheading(random.randint(0, 360))  # from where it collidee's it goes 360 moves location 360 Right

    def move(self): # we copyed the same method cause it will be doing the same movements as the player we want it to go "forward" with our set "speed" & also check for our borders we set
        self.forward(self.velocity)

        # Border Checking
        if self.xcor() > 290 or self.xcor() < -290:  # Left side is -290 Right side is 290 we also want the coordinates x and y to be below 300 to not go over our border
            self.left(60)
        if self.ycor() > 290 or self.ycor() < -290:
            self.left(60)

# Collision checking function/Method
# Uses the Pythgorean Theorem to measure the distance between two objects

def isCollision(t1, t2):  # t1 = turtle1 t2 = turtle also when a function starts with  "is" isCollision most likely it will be a Boolean of True or False
    a = t1.xcor()-t2.xcor()  # xcor = Right -xcor = Left/ when they collide the xcor is 0
    b = t1.ycor()-t2.ycor()  # ycor = Right -ycor = Left/ when they collide the ycor is 0
    distance = math.sqrt((a ** 2) + (b ** 2))

    if distance < 30:
        return True
    else:
        return False

# Create class instances
player = Player()  # after creating a class must make instances to call it in other words make an Object of the class
border = Border()  # sub class
#goal = Goal()  #sub class
# Draw our border
border.draw_border()

#create multiple goals
goals = []  # Creating a list of goals
for count in range(6):  # We are making the code repeat 6 times
    goals.append(Goal()) # each time the code runs it puts a goal the end 6 times

# Set keyboard bindings
ms.listen()
ms.onkey(player.turnleft, "Left")
ms.onkey(player.turnright, "Right")
ms.onkey(player.increasespeed, "Up")

# speed game up
ms.tracer(0.1)

# main loop
while True:
    ms.update()
    player.move()  # these two are class methods
    #goal.move()  # the reason we copyed like we said is cause it's gunna have the exact same movements as our player!
    # we want the goal to be True to in our while loop in order for the code to be excuted
    for goal in goals:
        # Basically saying If there is a collision between the player and goal we the want the goal to "jump" / Function in our while True loop
        goal.move()
        if isCollision(player, goal):
            goal.jump()  # baiscally saying if the goal collide's move or "jump" to other location

    time.sleep(0.005)