1 00:00:00,300 --> 00:00:02,250 Now that we've created both paddles 2 00:00:02,310 --> 00:00:07,020 the next obvious step is to create the ball and get it to move. 3 00:00:07,500 --> 00:00:12,500 So this ball is going to be created as a separate ball class and the ball object 4 00:00:14,550 --> 00:00:19,350 that we're going to create from it will have a width of 20, height of 20, and it's 5 00:00:19,380 --> 00:00:23,310 X and Y position will start out at the center of the screen, 6 00:00:23,490 --> 00:00:27,300 so (0, 0). Now when the screen refreshes, 7 00:00:27,300 --> 00:00:32,299 the ball is automatically going to move on the screen and it's going to move up 8 00:00:33,390 --> 00:00:34,920 and also to the right. 9 00:00:34,920 --> 00:00:39,920 So it's X and Y positions will change on every refresh of the screen. 10 00:00:40,800 --> 00:00:45,000 So this is going to be a little bit more challenging and will require a little 11 00:00:45,000 --> 00:00:46,320 bit of thinking from your part. 12 00:00:46,680 --> 00:00:51,390 But I want you to pause the video and give this problem a bit of thought and see 13 00:00:51,390 --> 00:00:55,590 how far you can get in trying to get the ball to move to the top- 14 00:00:55,620 --> 00:00:59,580 right edge of the screen. Pause the video and give that a go. 15 00:01:03,260 --> 00:01:05,330 All right. So to start off, this time 16 00:01:05,330 --> 00:01:10,250 I'm going to create a ball.py file and inside 17 00:01:10,280 --> 00:01:14,330 this ball.py is where we're going to create our ball object. 18 00:01:14,750 --> 00:01:15,830 So firstly, 19 00:01:15,830 --> 00:01:20,830 I'm going to import my turtle class and then I'm going to create my ball class 20 00:01:22,040 --> 00:01:24,320 which is going to inherit from the turtle class. 21 00:01:24,800 --> 00:01:28,130 And then I'm going to do all of the usual initialization. 22 00:01:30,440 --> 00:01:33,950 And now we're ready to create our ball class. 23 00:01:34,430 --> 00:01:39,080 This ball is going to, firstly, have a white color. 24 00:01:39,710 --> 00:01:44,300 And in addition, it's going to have a shape that is going to be a circle. 25 00:01:44,600 --> 00:01:47,510 Now I know that in the original pong game, 26 00:01:47,600 --> 00:01:52,250 the table tennis ball is actually a square. So you can keep it a square 27 00:01:52,250 --> 00:01:56,300 if you want to be historically accurate, or you can change it to 28 00:01:56,300 --> 00:02:00,650 a circle like I have here to make it look more like a ping pong ball. 29 00:02:01,370 --> 00:02:02,360 Now, in addition, 30 00:02:02,390 --> 00:02:06,980 we're going to need to get it to pen up so that it doesn't end up drawing across 31 00:02:06,980 --> 00:02:07,813 the screen. 32 00:02:08,210 --> 00:02:13,210 And now all we need is to initialize our ball from the ball.py 33 00:02:17,870 --> 00:02:20,600 and we're going to do that just below our paddles. 34 00:02:20,660 --> 00:02:24,500 So I'm going to create a new ball object from the ball class. 35 00:02:25,010 --> 00:02:26,390 And now if I hit run, 36 00:02:26,420 --> 00:02:30,380 you'll see our circular ball show up in the center of the screen. 37 00:02:31,430 --> 00:02:36,430 The next problem is how do we get the ball to move towards the top right corner 38 00:02:37,310 --> 00:02:38,143 of the screen? 39 00:02:38,360 --> 00:02:42,500 So that's going to involve a change in the X coordinate as well as the Y 40 00:02:42,500 --> 00:02:45,590 coordinate. In our while loop here 41 00:02:45,740 --> 00:02:47,720 where our screen is updating, 42 00:02:48,050 --> 00:02:51,410 we're going to call a method in the ball class 43 00:02:51,710 --> 00:02:56,000 which is going to be called move. And this move method 44 00:02:56,030 --> 00:03:01,030 which we'll define now is going to be responsible for moving our ball. 45 00:03:02,290 --> 00:03:07,290 And the way that it's going to move is it's going to increase on the X and also 46 00:03:08,350 --> 00:03:12,790 increase on the Y. Let's create a new X coordinate 47 00:03:12,820 --> 00:03:17,820 which is going to be the current self.xcor plus a arbitrary amount. 48 00:03:18,850 --> 00:03:20,770 So let's say increase by 10. 49 00:03:21,220 --> 00:03:26,220 And then the new Y is going to be the self.ycor increased by the same 50 00:03:27,730 --> 00:03:30,160 arbitrary amount. And then finally, 51 00:03:30,190 --> 00:03:35,190 we can get our ball to go to this new X and new Y. 52 00:03:37,690 --> 00:03:39,640 So now when we run our code, 53 00:03:39,880 --> 00:03:44,500 you can see that our ball immediately goes off the screen to the top right 54 00:03:44,500 --> 00:03:48,130 corner. If we want the ball to slow down a little bit, 55 00:03:48,190 --> 00:03:50,950 we can do one of two things. Either 56 00:03:50,980 --> 00:03:55,980 we can go into the move method and change this 10 here to say a 1. 57 00:03:57,010 --> 00:04:01,360 That way, every time our loop runs, our ball will only move one pixel. 58 00:04:02,080 --> 00:04:06,490 Alternatively, we can pause the loop for a short time during each iteration. 59 00:04:07,480 --> 00:04:10,180 Moving the ball at a tiny amount does work, 60 00:04:10,330 --> 00:04:14,350 but I'm going to go with the second option and import our time module. 61 00:04:14,770 --> 00:04:18,790 Then I'm going to get our while loop to sleep for a little bit in between each 62 00:04:18,790 --> 00:04:19,690 of the updates. 63 00:04:20,320 --> 00:04:24,460 So, I normally start off with just a 0.1 second sleep, 64 00:04:24,790 --> 00:04:28,450 and you can see now a ball moves at a more reasonable pace 65 00:04:28,720 --> 00:04:31,690 and we actually have a chance of catching it with one of the paddles. 66 00:04:32,530 --> 00:04:37,210 That's all there is to it. We've now created on the ball class, initialized 67 00:04:37,270 --> 00:04:42,270 a ball object and we've got the ball to move on every refresh of the screen.