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Scratch variables - Contenido educativo

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Subido el 10 de noviembre de 2024 por Juan Carlos A.

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Hello, in this video tutorial we're going to use some variables. First of all, we use a variable to take account of the lives the cat is going to have, because the cat is going to die. 00:00:00

and after that we will use another variable to score some points 00:00:16

and even later on we will use yet another variable to increase the difficulty 00:00:24

but using a countdown with a timer 00:00:32

so we will have a fixed time to complete our task at the video game 00:00:36

so as you may notice I've already placed the blocks for the motion here with the 00:00:43

right arrow, left arrow, up arrow and down arrow as we have done so many times 00:00:51

now I've placed the cat at the starting point, right there, with the 00:00:57

rotation style left to right so it doesn't go upside down when going left 00:01:09

and already start included the first of three backdrops I got three backdrops 00:01:14

here, well, I'll remove this one, I'll make one later, one of this, first the bulwark, 00:01:28

then the MIT field, and then the forest. So we'll start at the bulwark and as the 00:01:40

cat moves, if it reaches an edge, the right edge, then it will go to the next 00:01:49

backdrop and as it is it's exiting from the right side it will appear on the 00:01:55

left side and conversely if it exits from the left edge it will appear on the 00:02:02

right edge and on the previous background so change of backdrop motion and then I've 00:02:10

I have already defined a block here for the cat to die in this way, playing a meow sound, and then I will rotate it, setting the rotation style all around, make it point upwards, and disappear with the ghost effect. 00:02:17

Something like this. 00:02:37

It's always good to check that you are doing things. 00:02:40

Now, as I've included some ghost effects here, I will include also clear graphic effects at the beginning, so I got the cat not transparent from the beginning. 00:02:44

Let's check if this works, so I can move the cat every way and change backdrops back and forth. 00:02:56

and what am I going to do now I'm going to include another character let's say 00:03:06

well let's say I got the crab and I'm going to make it smaller so set size to 00:03:21

check it like 30% we click on it and check it well maybe too small let's say 00:03:38

40% something like that and I want it to appear only on the second backdrop let's 00:03:47

say so as the beginning we start at the first backdrop I can use for the crab 00:03:56

when switching backdrop to our place the second one fill up MIT then appear 00:04:07

success the 40 and show and now I'm going to duplicate this couple of times 00:04:18

and say that at the war walk and at the forest it will hide so it will only 00:04:30

appear there now I'm placing it somewhere let's say there so go to then I will use 00:04:46

a rotation style left right and now I'm going to move it in a random way by 00:04:58

bouncing with a forever move and if on edge bounce as we have already done in 00:05:06

previous exercises let's check it there's no crab here we're going to the 00:05:18

second backdrop there's the cat it's moving but it's pointing left and right 00:05:27

let's check what happened here I have to make it point at some angle so let's put 00:05:33

it here point at an angle so it will be bouncing there there it is okay now the 00:05:43

is anytime the cat touches the crab it dies I mean it lose it loses a life so 00:05:59

if I want the cat to have seven lives I have to create a variable so I can take 00:06:11

account of the number of lives that are left so I go into variables and make a 00:06:22

a variable I'm calling it lives left and now at the beginning I will set the 00:06:29

lives left to 7 and as I have ticket this is ticket the lives left appear on 00:06:43

screen I can move them well I can also change it make it like that right 00:06:55

clicking on it I can just put it normal readout now touching the crab okay as 00:07:06

have plenty of blocks here I will start a new thread and include a new forever 00:07:23

and in here I will be asking with an if if the cat is touching the crab that's 00:07:32

under ascension first block if touching crab touching crab what would happen 00:07:41

that the lives will change how? by minus 1 so change lives by minus 1 00:07:51

let's see what happens is it this one to work well not really but we'll learn 00:08:06

something okay so here we got seven lives we go there now first touch okay 00:08:13

we've lost nine lives in just one touch what why is this happening because all 00:08:22

the time the crab is going through the cat it keeps touching it and the program 00:08:31

accounts for several touches in one pass we want this to count just one so how 00:08:39

can we do that we can use a weight so it leaves some time for the crab to go away 00:08:48

from the cat or the cat away from the crab before counting again so let's say 00:08:57

a couple of seconds and see what happens okay lives left six why this should be 00:09:04

seven when clicking set lives to seven seven good now I haven't click it on the 00:09:14

green flag that was now there we go and now let's say one touch six lives five 00:09:26

lives. That's better. Four lives. Good. Now then, we have already defined a way to 00:09:41

die, but when is the cat going to die? Well, when it loses all the lives. So we have to 00:09:51

ask if lives get to zero. So if, an independent if in here, inside a forever. 00:09:57

we could place it in the separate one but we can use the same forever now if 00:10:07

operator equal green one zero what is going to be zero the variable lives we 00:10:14

go into lives into variable and get lives left if life let's get to zero 00:10:24

then die. We already got a block for that. Die. Check it. 7 lives, 6, not so difficult to avoid, 4, 3, 2, 1, and 0. 00:10:30

and now the cat dies 00:11:04

well, still, we might 00:11:10

want to have a second chance, second 00:11:14

opportunity, so how about if we make it start 00:11:18

all over when it gets to zero lives 00:11:22

when we did have some blocks here 00:11:26

that were the setup at the 00:11:30

beginning we can make a block for this setup at the beginning and call it start 00:11:34

so our start is going to be this placing the lives at 7 clearing the graphic 00:11:43

effects switch the back door to the first one 00:12:03

sabotage in style point and go and as we are switching back to broad walk the 00:12:07

crab would hide so that's good so there we go 00:12:17

oops why is it check it because if I define the start I have to use the block 00:12:21

here is the start I place it here when I begin I start and then after dying 00:12:35

we start again here as part of the dying because if I place the start here it will 00:12:44

start forever. That's all good. So, after dying it starts again. There we go. 00:13:00

Six, five, four, three, two, one, zero. Dying and starting again. Good. So now, let's say we want 00:13:17

to make it all more interesting and include some points for us to score 00:13:49

while we try to avoid the crab so if we are going to count let's say we we score 00:13:55

points by touching a different sprite 00:14:07

get some apple here and well this is the apple curve 00:14:13

let's say i want the apple to appear only at the same 00:14:23

backdrop so when backdrop switches to i place the 00:14:31

three of them and i use so for the second and 00:14:38

height for the first and third well now i'm going to place the apple somewhere let's say here 00:14:47

and also we'll use the rotation style left right go there point at an angle and move let's say 00:14:59

point and then continuous motion with a forever move and if on its bounds we'll 00:15:14

keep it simple let's check it okay so there we've got a crab and we are 00:15:25

already losing lives and the apple now let's say we grab the apple how can we 00:15:39

touch the apple how can we score points okay there we go so points those are 00:15:47

numbers another variable so I make a variable and call it the score now at 00:15:57

the beginning it's going to be zero so set again I'm here and then at the 00:16:08

apple's code I could also be the cat's code because when the cat touches the 00:16:20

apple the apple touches the cat. I have less blocks here so I'm going to use them here 00:16:29

so at the beginning I will set score to zero and now I'm 00:16:35

going to check if they are touching if touching cat which is called sprite1 00:16:50

then change the score by one I'm going to variables and change not lives but 00:17:03

score by one okay now we start we we got the score here we might want to hide 00:17:13

later well let's see if we are scoring some points we're not why okay it's not 00:17:28

working checking back to the code if touching change the score by one should 00:17:40

be working it's not okay okay that's it it's actually working maybe I forgot to 00:18:01

click the green flag whatever but then again remember if you don't use a weight 00:18:26

you will be counting too many times so every time it's touching it's counting 00:18:33

not one but plenty of points so in quite the same way as we use here a weight so 00:18:40

we weren't losing the lives several at the time we go here and use a weight 00:18:51

again let's say a couple of seconds okay good now as I said I want lives on the 00:18:59

score to appear only on this backdrop because there's no reason for them to be 00:19:15

here well maybe the likes yes but the score is not there well let's well you 00:19:20

might want it to be from the beginning but if you don't you can go into 00:19:31

variables and use show and hide variables so you can show variables 00:19:35

score and on this backdrop and hide variables score on this other two that 00:19:45

way you get the variables just on the 00:19:58

background in which they are counting 00:20:03

there okay now what happens if you get 00:20:09

some score let's say let's say if we get 00:20:16

to ten points we we win so let's create 00:20:25

a final backdrop like I win first of all if we want to paint it with a packet 00:20:34

it's not working here we have to convert it to bitmap first remember convert to 00:20:46

bitmap now we can paint it now we can type some letters with a 00:20:53

different color okay like that let's say I wait now if you use the arrow pointer 00:21:00

and select it by dragging you can use a handle and make it big place then when 00:21:17

you win you might want the other characters to disappear so let's get back here and say 00:21:34

when but the switch is the high uh that the ios one okay so they they will disappear okay um now 00:21:45

Now, checking, scoring 5, lives left 3, oops, score 7, oops, score 8, oops, lives scored, ah, oops, 9, ah, yeah, and that's just what I was, well, but, 00:22:14

But you just try. Now, let's make it a little more difficult. Let's get a fixed time for us to cross through the second backdrop. Right? So, how do we count time? We count time with a timer. This is under a sensor. This is a timer. 00:23:12

Timer counts up. You can restart it from zero. It gets plenty of decimals. It goes one second and decimal points of a second. Even milliseconds. Too many numbers. 00:23:33

Then it's counting up. We want our time to count down. So we are going to use a variable. Well, where? There are too many blocks here. Let's go somewhere else. Like here, there, here. Let's say here. 00:23:50

So, let's say we create a variable, look, we are creating a variable for all sprites. 00:24:11

That's why we can create it at the graphs code or any other one, because it will work 00:24:23

for all. 00:24:29

So we leave this mark for all sprites. 00:24:31

We will be calling it timeLeft, right. 00:24:35

So now, let's say, we're going to count time from, let's say, 60 seconds, so we will make 00:24:43

time, we will set the time left to 60 minus the time that counts the timer. 00:24:53

we subtract because we wanted to count backwards we wanted to count down so if 00:25:09

we start at 60 and we put here the timer which is under sensing the time left 00:25:16

will be going down if we put this inside a forever and put it like we can put it 00:25:29

in another when backdrop switches or we can put it from the beginning and say 00:25:49

that the timer restart will reset the timer when we enter the backdrop 00:26:00

whatever see now we got it's not showing the time here 00:26:09

set time left to 60 minus timer but I guess it's not actually counting 00:26:29

properly because the timer is a different number so we will round it and 00:26:43

remove the decimal points we go into math operators and use round 00:26:49

still not working still not working why because oh because this is life left I 00:27:08

haven't changed it to time left I forgot okay that's it now at the beginning it's 00:27:30

counting down right but then it will reset and start counting from 60 so what 00:27:39

do we have to do? We have to remove this variable from this backdrop and only 00:27:49

show it when it starts at 60 here and counting down. So we use the same trick 00:27:57

we did before and use under variables, hide variable and show variable. Show 00:28:05

So variable here, hide variable on the other and now we can remove the timer by unticking 00:28:12

it. 00:28:29

That's it. 00:28:31

There. 00:28:33

I have to stop it and then, okay, that's it. 00:28:34

Well there we go. 00:28:42

Lives left and time left but then when we hit the green arrow there's only, no there's 00:28:44

three lives, not time 00:28:51

ok, same thing as before, I have to change the variable number 00:28:55

name here, it's time, time 00:28:59

and time, and 00:29:03

so time left, and we also want to show lives left 00:29:09

ok, so 00:29:14

so lives left in here, hide 00:29:18

so let's check this again at the second backdrop we show lives and time and on 00:29:22

the other backdrops we hide both of them place it no variables then time box we 00:29:40

should move them so we can see all of them. Lives, score, and time. There we go. We lose 00:29:56

some lives, we score some points, the time goes down, and well, now there's only one 00:30:18

left for us which is if the time runs out then we die we have already used if 00:30:29

lives left 0 then die we can place the if time left is 0 die in here if equal 00:30:41

operator equal to zero, variables, time left, then block die, and when dying, win. 00:31:00

So that should be it. There we go. We've got three variables working. The score, the time, 00:31:24

Time and lives. If I get a score, I win. If not, I die and I get a try again. 00:31:33

Oops. They are too close. Oops. 00:31:50

Well, that's all. Thank you. 00:31:58

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