Start a new Scratch project, and delete the cat sprite so that your project is empty. You can find the online Scratch editor at jumpto.cc/scratch-new.

Add in a new balloon sprite, and a suitable stage backdrop.

Add this code to your balloon, so that it bounces around the screen:

    when flag clicked
    go to x:(0) y:(0)
    point in direction (45 v)
    forever
        move (1) steps
        if on edge, bounce
    end

Test out your balloon. Does it move too slowly? Change the numbers in your code if you want to speed it up a bit.

Did you also notice that your balloon flips as it moves around the screen?

Balloons don’t move like this! To fix this, click on the balloon sprite icon, and then click the blue i information icon.

In the ‘rotation style’ section, click the dot to stop the balloon rotating.

Test your program again to see if the problem is fixed.

With the code you have now, your balloon will always start in the same place and move in the same path. Click the flag a few times to start your program, and you’ll see it’s the same every time.

Instead of using the same x and y position each time, you can let Scratch choose a random number instead. Change your balloon’s code, so that it looks like this:

    when flag clicked
    go to x:(pick random (-150) to (150)) y:(pick random (-150) to (150))
    point in direction (45 v)
    forever
        move (1) steps
        if on edge, bounce
    end

If you click the green flag a few times, you should notice that your balloon starts in a different place each time.

You could even use a random number to choose a random balloon colour each time:

    change [colour v] effect by (pick random (0) to (200))

What happens if this code is put at the start of your program? Does anything different happen if you put this code inside the forever loop? Which do you prefer?

Click on your balloon sprite, and then click the ‘Costumes’ tab. You can delete all of the other costumes, just leaving 1 balloon costume. Add a new costume, by clicking ‘Paint new costume’ and create a new costume called ‘burst’.

Make sure that your balloon switches to the right costume when the game starts. Your code should now look like this:

    when flag clicked
    switch costume to [balloon1-a v]
    point in direction (pick random (-90) to (180))
    go to x:(pick random (-150) to (150)) y:(pick random (-150) to (150))
    change [color v] effect by (pick random (0) to (200))
    forever
        move (1) steps
        if on edge, bounce
    end

To allow the player to burst a balloon, add this code:

    when this sprite clicked
    switch costume to [burst v]
    play sound [pop v]

Test out your project. Can you pop the balloon? Does it work as you expected? You’ll need to improve this code, so that when the balloon is clicked, it shows the ‘burst’ costume for a short time, and is then hidden. You can make all of this happen by changing your balloon when sprite clicked code to this:

    when this sprite clicked
    switch costume to [burst v]
    play sound [pop v]
    wait (0.3) secs
    hide

Now that you’re deleting the balloon when it’s clicked, you’ll also need to add a show block to the start of the when flag clicked code.

Try popping a balloon again, to check that it works properly. If you find it difficult to pop the balloon without dragging it around, you can play the game in fullscreen mode by clicking this button:

A much better way of getting lots of balloons is to clone the balloon sprite.

Drag your balloon when flag clicked code (except the score block) off of the event (don’t delete it), and instead add code to create 20 balloon clones.

You can now attach the code you’ve just removed to the when I start as a clone event. You should also replace the hide block in the balloon-clicking script with a delete this clone block.

Your balloon code should now look like this:

Test your project! Now when the flag is clicked, your main balloon sprite will hide and then clone itself 20 times. When each of these 20 clones is started, they will each bounce around the screen randomly, just as they did before. See if you can pop the 20 balloons!

You can use another variable to store the remaining time left. Click on the stage, and create a new variable called ‘time’:

This is how the timer should work:

• The timer should start at 10 seconds;
• The timer should count down every second;
• The game should stop when the timer gets to 0.

Here’s the code to do this, which you can add to your stage:

    when flag clicked
    set [time v] to [10]
    repeat until <(time) = [0]>
        wait (1) secs
        change [time v] by (-1)
    end
    stop [all v]

To add the repeat untiltime= 0 code, first you’ll need to drag a green = block, onto your repeat until block:

You can then drag your time variable onto the = block:

Drag your ‘time’ variable display to the right side of the stage. You can also right-click on the variable display and choose ‘large readout’ to change how the time is displayed.

Test your game. How many points can you score? If your game is too easy, you can:

• Give the player less time;
• Have more balloons;
• Make the balloons move faster;
• Make the balloons smaller.

Test your game a few times until you’re happy that it’s the right level of difficulty.