WEBVTT 0 00:00.180 --> 00:02.010 So we figured out how to detect 1 00:02.040 --> 00:07.040 collision with the top and bottom walls and make our ball bounce off the walls. 2 00:07.470 --> 00:11.550 The next thing we need to do is to detect when there's a collision with the 3 00:11.550 --> 00:14.970 paddle and make the ball bounce off the paddle. 4 00:15.630 --> 00:18.840 This is probably going to be the hardest part of this program yet 5 00:19.080 --> 00:21.600 so I wanna talk you through the logic. Now, 6 00:21.630 --> 00:25.650 how can we know when the ball has hit the paddle? Now, 7 00:25.680 --> 00:30.680 normally we use the distance method to check what is the distance between the 8 00:30.690 --> 00:34.680 ball and the paddle. And if it's less than a certain amount, 9 00:34.710 --> 00:38.670 then we can be relatively sure that they've made contact with each other. 10 00:39.360 --> 00:42.540 So the code that we normally use would be something like this. 11 00:42.960 --> 00:47.190 We get our ball and we check its distance from the paddle. 12 00:47.820 --> 00:52.820 Now remember that our ball has a width of 20 pixels and our paddle has a 13 00:54.150 --> 00:57.930 width of 20 pixels. Normally we would say, well, 14 00:57.960 --> 01:02.430 if that distance between the two of them is less than 20, well, 15 01:02.430 --> 01:04.500 then they've probably made contact, right? 16 01:05.040 --> 01:09.300 But the problem occurs when the ball hits the paddle, not right in the center, 17 01:09.390 --> 01:11.370 but at the edge of the paddle, 18 01:11.760 --> 01:16.500 because this distance measures the center of the ball from the centre of the 19 01:16.500 --> 01:18.570 paddle as the distance. 20 01:18.600 --> 01:22.140 So you can see that this distance is way bigger than 20, 21 01:22.410 --> 01:25.200 so it's not going to register as a collision. 22 01:26.280 --> 01:28.920 How can we solve this problem? Well, 23 01:28.950 --> 01:33.150 we could add on an additional condition. We could check well 24 01:33.150 --> 01:38.150 if the ball has gone past a certain point on the X-axis, 25 01:38.700 --> 01:43.700 if it's gone far enough over to the right and it's within a 50 pixel distance of 26 01:44.880 --> 01:45.713 the paddle, 27 01:45.750 --> 01:50.750 then that also means it's made contact with the paddle. Inside our main.py 28 01:52.260 --> 01:57.260 I'm going to add a comment to detect collision with right paddle. 29 02:00.120 --> 02:04.200 So let's experiment with some numbers here and see if we can get the ball to 30 02:04.200 --> 02:06.720 bounce off the paddle. In this case, 31 02:06.750 --> 02:11.750 we're going to check if the ball.distance to the r_paddle is less than 32 02:15.570 --> 02:20.570 50 and the ball.xcor is greater than 340. 33 02:24.060 --> 02:25.830 If the ball has hit the right paddle, 34 02:26.040 --> 02:30.840 let's print something to the console to test our code. Let's print made contact. 35 02:32.940 --> 02:37.260 So if we run this code and I manage to make contact with the ball, 36 02:37.530 --> 02:41.910 you can see that it says 'Made contact' in our console. 37 02:42.390 --> 02:44.850 So instead of just printing made contact, 38 02:44.970 --> 02:49.650 what we want the ball to do is to again, to bounce. Now, 39 02:49.680 --> 02:52.680 this bounce is a little bit different from the last bounce, 40 02:53.040 --> 02:58.040 because the previous one was changing its Y coordinate so that it moved in the 41 02:58.470 --> 03:02.830 opposite along the vertical. But in this case, 42 03:02.860 --> 03:07.420 we actually want it to move along the opposite direction in the horizontal 43 03:07.420 --> 03:09.940 because the paddle is here and the ball is coming this way, 44 03:10.120 --> 03:14.590 we want it to go back this way. So instead of just calling this bounce, 45 03:14.620 --> 03:19.360 I'm going to right-click on it and then refactor and rename to bounce_ 46 03:19.420 --> 03:23.860 y because this is bouncing in the Y-axis. Now, 47 03:24.220 --> 03:28.120 once we hit refactor, it'll change it here and it will change it here. 48 03:29.770 --> 03:33.460 Now on top of that, I'm going to define my bounce_x, 49 03:33.730 --> 03:37.600 so it bouncing in the X-axis, and this is very similar. 50 03:37.630 --> 03:39.910 We're going to change the x_move, 51 03:39.940 --> 03:44.940 so the amount that the ball moves each time when the move method is called and 52 03:45.340 --> 03:48.100 I'm going to multiply it by -1, 53 03:48.430 --> 03:51.160 so reversing the X direction. 54 03:51.850 --> 03:54.760 And then when our collision is detected, 55 03:54.790 --> 03:58.660 we're going to get the ball to bounce in the X direction. 56 03:59.440 --> 04:01.360 So now if we run our code, 57 04:01.390 --> 04:04.930 you can see that even though this only works on the right paddle, 58 04:05.200 --> 04:07.030 when the ball hits the right paddle 59 04:07.270 --> 04:11.500 it moves back and it bounces back towards the left. 60 04:11.860 --> 04:16.570 It changes the direction that it was moving in the X-axis. 61 04:17.740 --> 04:22.740 So now lets add the collision for both paddles because they both need to bounce 62 04:25.690 --> 04:26.920 in the X-axis 63 04:27.280 --> 04:32.280 and so we're going to tag onto this a 'or' statement and we're going to say 64 04:32.410 --> 04:37.410 or if the ball.distance to the left paddle is also less than 50 65 04:41.860 --> 04:43.300 and on top of that 66 04:43.450 --> 04:48.450 the ball.xcor is less than -340. 67 04:53.080 --> 04:58.080 So this basically checks to see if the ball has gone far enough to the left as 68 04:58.360 --> 05:03.360 to be past the paddle and its within a distance of 50 pixels from the left 69 05:05.230 --> 05:08.080 paddle. So if we run the code right now, 70 05:08.110 --> 05:12.370 you can see that not only does our ball bounce when it hits the right. 71 05:14.230 --> 05:16.630 So now when we run the program again, 72 05:16.660 --> 05:20.500 you can see that not only does the ball bounce on the right paddle, 73 05:20.740 --> 05:24.940 it also bounces when it hits the left paddle. 74 05:26.170 --> 05:30.370 Now there's a little bit more tweaking that we can do with the coordinates because 75 05:30.370 --> 05:33.160 you can see that when the ball hits the paddle, 76 05:33.220 --> 05:38.220 it goes a little bit too far before it actually reverses direction. 77 05:39.160 --> 05:44.160 So we can change this to a slightly smaller number if we want it to bounce 78 05:45.580 --> 05:48.370 before it's within the actual paddle. 79 05:48.700 --> 05:53.700 So we can change this to 320 and this one also to 320 and notice what 80 05:55.000 --> 05:59.000 happens now. Before it hits the actual paddle, 81 05:59.180 --> 06:04.180 it now actually bounces and it doesn't look like as if the ball's fallen into the 82 06:05.120 --> 06:08.960 paddle before it turns back. And there you have it. 83 06:09.080 --> 06:12.530 Now we just have to figure out what should happen when the paddle misses the 84 06:12.530 --> 06:16.220 ball. For all of that and more, I'll see you in the next lesson.