WEBVTT 00:00.000 --> 00:22.600 All right. Welcome back. So, you've created your scratch account, and we've learned how 00:22.600 --> 00:28.320 the scratch dashboard on the whole screen here is organized. Now, in this video, I'm 00:28.320 --> 00:32.080 going to teach you how the scratch blocks work, and we're going to program this 00:32.080 --> 00:37.080 little cat on the screen to do various things. By the end of this chapter, you'll 00:37.080 --> 00:41.040 have a pretty good idea of how scratch blocks work, so that later in the course 00:41.040 --> 00:48.240 we'll go on to create more complicated things like apps and games. So go ahead and 00:48.240 --> 00:52.200 select the sprite here if it's not selected already, and then go to the events 00:52.200 --> 00:56.520 section, which is this yellow section here in the code, and then click on this 00:56.520 --> 01:03.920 one flag, click block, and drag it all the way to the empty space. So, this is how 01:03.920 --> 01:08.280 we will program by dragging various blocks here from the left hand side, all the 01:08.280 --> 01:14.080 way to the empty space where our code is going to be for the sprite. Then, I want 01:14.080 --> 01:18.960 you to go to the sensing section, which is this light blue section, and drag the 01:18.960 --> 01:23.880 ask, what's your name and weight, and snap it right below the window, fly clicked, 01:23.880 --> 01:29.880 so notice that various code blocks will fit into one another like puzzles or 01:29.880 --> 01:36.520 Lego pieces. Then, I want you to go to the look section, which is this purple 01:36.520 --> 01:43.720 section, and drag this say hello for two seconds block, and snap it right below. 01:44.520 --> 01:49.320 So this will be our first script, which says the following. When the green flag is 01:49.320 --> 01:53.960 clicked, the cat will ask for our name, and then wait, and after we've completed 01:53.960 --> 01:59.560 our name, the cat will say hello for two seconds. So, this is how code works, these 01:59.560 --> 02:04.560 code blocks are executed one after another. So, let me show you, I'm going to click 02:04.560 --> 02:07.960 on the green flag, and the cat's going to do exactly what the script is going to 02:07.960 --> 02:13.640 say. So, when the fake clicked, the cat will ask for my name, I'm going to type 02:13.640 --> 02:18.960 in my name here, and I say Daniel, and then I'm going to hit enter, then the cat will 02:18.960 --> 02:23.960 say hello for two seconds. So, the cat says hello, and after two seconds, the bubble 02:23.960 --> 02:29.440 disappears. Alright, so this was our first script. Let's make the cat do something a little 02:29.440 --> 02:35.880 bit smarter this time. So, let's go to sensing here in the light blue section, drag this 02:35.880 --> 02:41.280 rounded answer block and watch where I'm putting it. I'm putting it right where hello 02:41.280 --> 02:47.200 is, see how hello lit up. That basically is a signal that you can snap in this answer 02:47.200 --> 02:54.360 block, where hello is so snap ID like I do. So, the cat, instead of saying hello, is 02:54.360 --> 02:59.680 going to see the answer, whatever I type here, back to me. So, if I click on the green flag 02:59.680 --> 03:05.080 now, the cat will ask for my name, and wait. I'm going to type in my name, Daniel, and 03:05.080 --> 03:12.640 watch what a cat does. It said Daniel back to me. Right, so, at this point, we programmed 03:12.640 --> 03:17.840 the cat to echo back whatever we typed. It's question, what's your name? Let's make 03:17.840 --> 03:22.880 the cat do a proper greeting by saying hello, Daniel, instead of saying basically Daniel 03:22.880 --> 03:32.000 back to me. So, go to this operator's green section, and pull in the join block. Notice 03:32.000 --> 03:38.200 that this is also a rounded block. So, pulling into the empty space. So, I'm going to take 03:38.200 --> 03:42.880 the answer from the same block, and I'm going to snap it here at the second hole of the 03:42.880 --> 03:50.480 join block. And in the first hole of the join block, I'm going to say hello, and then 03:50.480 --> 03:55.160 I'm going to put in a comma here. Then I'm going to take this whole green block, and 03:55.160 --> 04:01.680 I'm going to snap it where hello is. So, at this time, the cat will do something a little 04:01.720 --> 04:07.360 bit differently. It will still ask for my name and wait, and after I'm done typing, instead 04:07.360 --> 04:12.760 of seeing the answer back to me, it will join. Hello, comma answer, and then save that 04:12.760 --> 04:18.180 back to me for two seconds. Let me show you. So, I'm going to click on the flag. The cat 04:18.180 --> 04:23.360 asks for my name, I'm going to type it back. Daniel, and after I hit enter, the cat 04:23.360 --> 04:31.000 will say hello, comma Daniel. All right, so we programmed the cat to do a proper greeting, 04:31.000 --> 04:36.560 depending on our name, the cat is now polite enough to say hello to our name back. Now 04:36.560 --> 04:40.640 what I'm going to do is I'm going to drag these two blocks away from the window, far 04:40.640 --> 04:46.560 clicked so that when the flag is clicked, these two blocks will not get executed anymore. 04:46.560 --> 04:51.040 And I'm going to make this cat move a bit on the screen, so I'm going to go to this top 04:51.040 --> 04:57.520 motion section, and I'm going to drag in the move 10 steps block and snap it below the 04:57.520 --> 05:03.480 window. Flag clicked, so now when I click the green flag, the cat will move 10 steps in 05:03.480 --> 05:09.920 its natural direction, which is right in this case. So let me click the flag and watch 05:09.920 --> 05:16.000 the cat very closely. Click. So, notice that the cat moved slightly to the right a little 05:16.000 --> 05:21.760 bit. If I click on the green flag again, the cat will move again. So, I'm going to click 05:21.760 --> 05:25.880 it a bunch of times, and you see that the cat is still moving. Now I'm going to play 05:25.920 --> 05:30.880 around with the cat a little bit. I'm going to add some rotation to the cat as well. 05:30.880 --> 05:35.480 I'm going to drag in this turn right 15 degrees, and I'm going to snap it below the move 05:35.480 --> 05:40.280 block, and I'm going to change the number of steps it moves to the right instead of 10. 05:40.280 --> 05:46.880 I'm going to do 30. So now, when the flag is clicked, the cat will move 30 steps in 05:46.880 --> 05:52.080 its direction, and then it will turn right by 15 degrees. Now, if you don't know what 05:52.080 --> 05:57.680 degrees are, we're going to learn everything about them later on in the course. Alright, 05:57.680 --> 06:02.960 so don't worry, 15 degrees means slightly to the right. Okay, so now when I click the 06:02.960 --> 06:07.240 green flag, the cat will move a bit, and it will turn a bit. So you see it move to the 06:07.240 --> 06:11.040 right, and then it turned to the right a little bit. And if I click the flag a bunch of 06:11.040 --> 06:16.200 times, you see that the cat is turning around in circles. Now I'm going to do something 06:16.200 --> 06:20.840 pretty interesting. Instead of me clicking the flag a bunch of times, and the cat rotating 06:20.840 --> 06:25.640 in a little bit at every one of my clicks, I'm going to make the cat do these things 06:25.640 --> 06:31.440 a number of times on its own. Watch what I'm doing. So I'm going to go to control this 06:31.440 --> 06:36.240 orange section over here, and I'm going to pull in the repeat 10 block and watch how 06:36.240 --> 06:47.240 I'm dragging it. I'm going to drag it right here to wrap around these two blue blocks. 06:47.240 --> 06:51.840 So if you're reading the script, it does exactly what it says when the flag is clicked. 06:51.840 --> 06:56.640 These two blue blocks will be repeated 10 times. So if I click on the green flag now, watch 06:56.640 --> 07:02.240 what the cat does. See, it turns around in circles on its own, and the 07:02.240 --> 07:10.160 computer is fast enough so that the cat seems to be in motion. Now of course, you can play 07:10.160 --> 07:14.960 around with these values instead of 10 times. You can do 20 times, and what you'll end 07:15.000 --> 07:22.520 up with is more rotation. So notice that the cat will listen to what the script is saying. 07:22.520 --> 07:27.600 If you say repeat 20, the cat will repeat 20 times. If you say it a million times, the 07:27.600 --> 07:32.360 cat will simply rotate in circles a million times. You can even go as far as to notice 07:32.360 --> 07:36.960 what I'm doing. I'm dragging these two blocks outside. I'm going to put this repeat block 07:36.960 --> 07:42.280 right where it came from. So I'm going to make it disappear. And instead, I'm going 07:42.280 --> 07:49.640 to pull in this forever block. I'm going to snap it right below. When flat clicked, 07:49.640 --> 07:54.720 I'm going to pull these two blue blocks inside the forever block. So you probably have 07:54.720 --> 08:00.200 a good intuition of what this does when the flag is clicked, the cat will rotate in circles 08:00.200 --> 08:05.520 endlessly. So if I click on the flag, the cat just rotates around in circles. This 08:05.520 --> 08:12.920 is so nice. All right, now let me show you another trick. Go to the costume section 08:12.920 --> 08:19.760 right over here, the second tab over here. And notice that this cat has two costumes. 08:19.760 --> 08:25.680 So it has a costume, one in costume. Two. If I switch between these two costumes fast 08:25.680 --> 08:31.200 enough, you'll get the impression that the cat actually walks. So I'm going to go back 08:31.200 --> 08:37.160 to the code to this purple look section. And I'm going to pull in this very small next 08:37.160 --> 08:43.240 costume block. And I'm going to pull it right below the blue blocks inside the forever loop. 08:43.240 --> 08:51.200 So in the forever loop, we are moving 30 steps forward. We're turning 15 degrees to the 08:51.200 --> 08:56.160 right and we're switching to the next costume because the computer is so fast. These blocks 08:56.160 --> 09:02.680 will execute very quickly and will have the impression that the cat actually walks. 09:02.680 --> 09:09.680 So I'm going to click the green flag and show you how this works. So click and you see 09:09.680 --> 09:15.640 that besides walking in circles, the cat actually does appear to be walking, which is awesome. 09:15.640 --> 09:19.760 If you pay very close attention to this little sprite over here, the costumes are being 09:19.760 --> 09:25.760 switched so, so, so fast by the computer. And the impression is that the cat is animating 09:25.760 --> 09:31.080 its walk. So I'm going to stop this little script. All right, let's do something else 09:31.080 --> 09:37.360 now. So right now, when we run this program, when we click on the green flag, the cat never 09:37.360 --> 09:42.480 stops running around in circles. Let's make it controllable so that when we press space, 09:42.480 --> 09:49.840 the cat will stop and say hello to us. So here's how I'm going to go about doing it. 09:49.840 --> 09:54.600 I'm going to go to this orange control section and I'm going to pull in this if then else 09:54.600 --> 10:00.920 block and I'm going to put it into the open space for now. Notice that this block has 10:00.920 --> 10:05.040 a diamond-shaped hole in it. This will be the condition that we will fill in by going 10:05.040 --> 10:13.000 to the sensing light blue section. And I'm going to drag this diamond-shaped key space 10:13.000 --> 10:21.200 pressed and I'm going to snap it into the diamond-shaped hole here. So what this block 10:21.200 --> 10:26.760 does is, if the key space is pressed, then it's going to execute whatever code we put 10:26.760 --> 10:33.040 here into this big hole. It's going to execute the other bit of code that we put into the 10:33.040 --> 10:41.560 other hole. So when the key space is pressed, we want the cat to say hello. So we all go 10:41.560 --> 10:49.560 to looks and we'll drag in to say hello and snap it inside the big hole here. Otherwise, 10:49.560 --> 10:54.720 the cat will so continue to run around in circles, which means we're going to put these 10:54.720 --> 11:01.280 three blocks inside the LS section in this block. So notice that this block has gotten 11:01.280 --> 11:07.440 quite big. Now, I'm going to snap this if then else block inside the forever loop. So 11:07.440 --> 11:12.920 now the script has gotten a little bit complicated. Now, when the flag is clicked forever, the cat 11:12.920 --> 11:20.440 is going to check the key space first. If so, then it will say hello and it will not 11:20.440 --> 11:26.960 do anything. Otherwise, it will continue to move 30 steps, turn a bit to the right and 11:26.960 --> 11:33.120 switch to the next costume. So, let's test it and click on the green flag. And because 11:33.120 --> 11:37.160 we're not pressing anything, the cat will still carry on going around in circles because 11:37.160 --> 11:42.640 the key space is not pressed. But notice what happens when I press the space bar. So three 11:42.640 --> 11:48.840 to one space. So, when I hold on and press the space bar, the cat stops in. It's running 11:48.840 --> 11:56.200 around in circles and stops to say hello. But when I lift my finger off the space bar, 11:56.200 --> 12:04.120 watch what happens. The cat will continue to walk around in circles. This may not be 12:04.120 --> 12:09.640 exactly what we want if we press the space bar. I'd like the cat to stop completely, not 12:09.640 --> 12:13.600 to continue running around in circles like crazy when I lift my finger off the space 12:13.600 --> 12:20.080 bar. So, here's what I'm going to do. I'm going to go to the control section, this orange 12:20.080 --> 12:29.200 section. And I'm going to pull in, stop and I'm going to snap it right below to say hello. 12:29.200 --> 12:35.120 And from the drop down, I'm going to select this script. So, if the space bar is pressed, 12:35.120 --> 12:42.160 then the cat will not move. It will say hello and it will stop this script. So, the script 12:42.160 --> 12:47.680 will not execute anymore. Let me go ahead and test this. So, I'm going to go to click 12:47.680 --> 12:52.720 the green flag. The cat is spinning around in circles like crazy and now I'm going to 12:52.720 --> 13:00.560 simply tap the space bar and not hold it. So, three to one go. So now the cat has fully 13:00.560 --> 13:05.060 stopped because of this little yellow block, the stop the script has executed, which 13:05.060 --> 13:08.320 stopped this whole complicated script altogether. 13:08.320 --> 13:14.640 Alright, so we've programmed a cat to do a lot of things in this video. I'm really 13:14.640 --> 13:19.000 proud of you of what we've done in just 10 minutes. Join me in the next video where 13:19.000 --> 13:22.160 I'm going to teach you some more tricks that we're going to use throughout the rest 13:22.160 --> 13:22.880 of this course.