Lesson video

Hello, everybody.

It's Mrs. Franzsen here.

Welcome to Computing.

It's really good to see you.

I'm glad to have you in my lesson today.

We're going to be doing some programming today, so let's get started.

By the end of this lesson today, you will be able to create a programme to move a sprite in all four directions.

Let's have a look at the keywords for this lesson.

The first word is algorithm.

An algorithm is a precise set of ordered steps which can be followed by a human or a computer to do a task.

The next keyword is sprite.

A sprite is a graphic object that can be controlled by a programme, and our little ladybug is an example of a sprite.

The next keyword is duplicate.

When you duplicate something, you copy it.

So to duplicate means to copy an exact part of a coding project.

In the first part of the lesson, we are going to select and resize a sprite.

This Scratch project is a maze.

The goal is to move a sprite from the start to the finish without touching any of the black lines.

Would this butterfly sprite work well for this project? Have a close look at this project and the butterfly sprite.

The sprite needs to fit between the black lines.

The butterfly sprite is too large.

It cannot fit between the lines.

The butterfly sprite needs to be resized.

Let's do a check here.

Which sprite is a suitable choice for this project? Is it A, B, or C? You can pause the video here to think about your answer.

Welcome back.

We were looking at which sprite was a suitable choice for this project.

The correct answer was A.

Why? The sprite has been resized to fit between the black lines.

Well done if you got that one right.

Watch this video on how to resize sprites.

In Scratch, sometimes when you work with sprites, they are not the size that you want them to be at.

This dog is too big to fit in my maze game.

If I use the size tool down here, I can adjust the size of the sprite.

The number starts on 100 as the value, so I'm going to half it, I'm going to put 50.

That shrinks the dog down to half the size it was before.

It is looking better, but it's still a bit big, so I'm gonna reduce that number even further.

I'm gonna change the value to 25.

Now we've got a very small dog.

If I want the dog to be a bit larger, I make the number higher, so I'm gonna change that to 30.

It's looking good.

It fits through all the parts of my maze.

Let's see if I can make it a little bit larger, to 35.

You can make the value higher or lower to resize your sprite until you're happy with the size that it is for what you need.

The maze design is a backdrop.

The backdrops are the costumes for the stage.

You can change how the stage looks by changing the backdrop.

To change a backdrop, select the stage.

The stage is over to the right-hand side of the screen.

Then select the Backdrop tab that is up at the top left of the screen with the paintbrush next to it.

To change the maze design, you can drag the lines to different spaces.

Use the line tool to add new lines.

Be careful to keep the maze fair.

The spaces shouldn't be too small.

Your sprite should still be able to fit in all of the spaces.

Use Undo to fix mistakes.

Let's do a check here.

The part of the project where you can change how the stage looks is called the.

Fill in the blank.

You can pause the video here to work on this question.

Welcome back.

The part of the project where you can change how the stage looks is called the backdrop.

Well done if you got that one right.

It's time for a task now.

I want you to open the Scratch project.

The project is called "Maze Project." Make your changes to the maze backdrop.

Add a sprite and resize it to fit your maze.

Make sure the sprite fits in all of the spaces in your maze.

Use Undo to fix any mistakes.

It's time to go and work on your project now.

You can pause the video and I'll be here when you get back.

Welcome back.

You worked really hard on setting up your maze project there, well done.

Here is a video demonstration of a maze backdrop and the sprite instructions.

This is the Maze Project task, Part A.

First of all, we're going to go to the stage.

It's selected, so it's purple, and we're gonna open up the Backdrop tab at the top.

You can see there are two copies of the maze backdrop so that you've got a spare copy.

If you use the cursor tool here, you can drag the lines to change the way that your maze is laid out, to change the shapes in your maze, and to make your maze easier or harder to complete.

Make sure you make small changes only because you don't want to make the maze far too difficult or far too easy.

You can use the line tool to add your own lines to the maze.

And remember, at the top we've got Undo and Redo if we make mistakes.

We get to go back one step or forward one step.

The next step is to add your sprite, so go down to the Choose a Sprite menu and press on the cat to open up the library.

Tap on the sprite that you want to select it.

Right, I'm testing the size of the sprite and you can see that it's too large.

If you go to the size box here, you can change the value.

If you make the value smaller, the sprite will go smaller.

And if you make the value larger, the sprite goes larger.

Now we want the sprite to be small enough to fit through the gaps in the maze.

The next step is to test the sprite by moving it through the maze to see if there are any parts where it might get stuck.

I'm going to open up my backdrops again and make some changes to the way my maze is laid out so that my sprite fits a bit better.

In the next part of the lesson, we will be looking at programming four-way movement.

In Scratch, sprites can be given code to move, using event blocks that run when a key is pressed.

In this way, we can create programmes that use the keyboard to move sprites.

So this code block here will move the ladybug up.

An algorithm is a precise set of ordered steps which can be followed by a human or a computer to do a task.

Here is an algorithm for moving a sprite to the right.

When the arrow key is pressed, one, make the sprite look to the right; two, move 10 steps.

How could you recreate this algorithm using Scratch blocks? Which blocks do you need? You can pause the video here to think about how you would answer this.

The programme starts with the "when key pressed" event block.

The next line uses the "point in direction" block.

In Scratch, 90 degrees is right.

The final line uses the "move 10 steps" block.

Watch this animation of the right direction movement code.

So as I tap on the right arrow key, the code is triggered and the sprite moves in that direction.

Let's do a check here.

True or false? The "when key pressed" block is a motion block.

Pause the video here to think about your answer.

Welcome back.

The "when key pressed" block is a motion block.

The answer is false.

Why? The "when key pressed" block is an event block.

Well done if you got that one right.

To get the sprite to move around the maze with the keyboard, you will need to make sure that the sprite has the correct code.

This code controls the movement to the right.

With some small changes, this code could control movement in another direction.

For your sprite to move in all four directions, your sprite will need four code sequences.

Once the code to move the sprite right is working correctly, you can then duplicate the code.

That was one of our keywords.

Duplicating means to copy exactly.

You can duplicate code or even duplicate sprites and their attached code.

Why would duplicating be useful? Pause the video and have a think about that.

Duplicating is a useful tool to save time.

Be sure to test your code and make sure it works correctly before you duplicate it.

If you're using a mouse, right click on a code sequence to open the Duplicate menu.

On a touch screen, tap and hold on a code sequence to open the Duplicate menu.

When you duplicate a code sequence, it creates an exact copy.

You can then change the copy, like adjusting the key and movement direction, to control the sprite in a new way.

You can see here that I duplicated my turn right and move right code, and now I'm going to make changes to that code.

Let's do a check here.

In Scratch, the tool that will make a copy is called.

Is it A, a replicate; B, a duplicate; or C, a reproduce? Pause the video and think about your answer.

Welcome back.

The correct answer was B, duplicate.

The duplicate tool will make an exact copy.

Well done if you got that one right.

It's time for a task now.

I want you to programme your sprite to use the correct direction movement programme.

I want you to test your programme to make sure it works correctly, then duplicate the programme three times to add movement for the left, up, and down directions.

Can you move your sprite around the maze using the keyboard without crossing the lines? It's time to go and work on your project now.

You can pause the video here and I'll be here when you get back.

Welcome back, I hope you enjoyed programming your sprite to move around the maze.

Let's watch a video demonstration of a four-way movement programme.

In this task, we are going to add movement code to our sprite to let it get around the maze.

So we're going to go to the Events tab first to find the "when key pressed" event.

We can change the key here to the right arrow.

Then we need some motion blocks, we need a "point in direction" block.

Remember, in Scratch, you can tap on the value here to check with the arrow which way you need to go, and then "move 10 steps." Let's test this programme, so I'm tapping with my keyboard and we know that's working correctly, so I can now duplicate it.

I right click to open that menu.

It gave me another copy of the same code, exact copy, which means I can save some time now, I only need to change two things in this code block.

I'm changing the direction and I changed the key as well.

I'm leaving the "move 10 steps." Let's test that as well.

So now my sprite can move to the right and to the left.

Let's duplicate again.

I'm gonna right click Duplicate, change it to the new direction, I'm gonna do up this time, so I need to change the value here for "point in direction." Pointing it up at 0 degrees.

Let's test that.

It's working great, just make some space here.

I'm dragging the work area across.

Duplicate, and zoom out a little bit to make some more room here.

Alright, on the last code block, I'm gonna use my final direction, which is down.

Change the value for "point in direction." Down is 180 degrees.

So my sprite now has four movement directions.

I can move up, down, left, and right.

The next part of the task is to see if you can use your controls that you've programmed to get your sprite all the way to the finish line without touching any of your black lines.

You have worked really hard on your learning today.

Let's summarise what we've learned.

In this lesson, an algorithm was first used to plan a sprite's movement.

The project involved selecting and resizing a sprite, then programming movement in the correct direction.

The duplicate feature was used to copy the movement code, which was then modified to control movement in all four directions.

This allowed the sprite to navigate the maze using keyboard inputs.

Thank you for joining me in this lesson today and I hope to see you again soon.