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.

Choose a character and a backdrop. Your character doesn’t have to be a person, but it needs to be able to show different colours.

In your game, you’ll use a different number to represent each colour:

• 1 = red;
• 2 = blue;
• 3 = green;
• 4 = yellow.

Give your character 4 different colour costumes, one for each of the 4 colours above. Make sure that your coloured costumes are in the right order.

To create a random sequence, you need to create a list. A list is just a variable that stores lots of data in order. Create a new list called sequence. As only your character needs to see the list, we can also click ‘For this sprite only’.

You should now see your empty list in the top-left of your stage, as well as lots of new blocks for using lists.

Add this code to your character, to add a random number to your list (and show the correct costume) 5 times:

    when flag clicked
    delete (all v) of [sequence v]
    repeat (5)
        add (pick random (1) to (4)) to [sequence v]
        switch costume to (item (last v) of [sequence v]
        wait (1) secs
    end

Notice that you have also emptied the list to begin with.

Add 4 sprites to your project, that will become buttons. Edit your 4 sprites, so that there’s 1 for each of the 4 colours.

When the red drum is clicked, you’ll need to broadcast a message to your character, letting them know that the red button has been clicked. Add this code to your red drum:

    when this sprite clicked
    broadcast [red v]

When your character receives this message, they should check whether the number 1 is at the start of the list (which means that red is the next colour in the sequence). If it is, you can remove the number from the list, as it’s been guessed correctly. Otherwise it’s game over!

    when I receive [red v]
    if <(item (1 v) of [sequence v])=[1]> then
        delete (1 v) of [sequence v]
    else
        say [Game over!] for (1) secs
        stop [all v]
    end

You could also display some flashing lights once the list is empty, as it means the entire sequence has been guessed correctly. Add this code to the end of your character’s when flag clicked script:

    wait until < (length of [sequence v]) = [0]>
    broadcast [won v] and wait

Click on your stage, and add this code to make the backdrop change colour once the player has won.

    when I receive [won v]
    play sound [drum machine v]
    repeat (50)
        change [color v] effect by (25)
        wait (0.1) secs
    end
    clear graphic effects

Add 2 new variables to your project, called high score and name.

If ever the game ends (by pressing the wrong button), you need to check whether the player’s score is higher than the current high score. If it is, you need to save the score as the high score, and store the name of the player. Here’s how your red button should look:

    when I receive [red v]
    if <(item (1 v) of [sequence v])=[1]> then
        delete (1 v) of [sequence v]
    else
        say [Game over!] for (1) secs
        if < (score) > (high score) > then
            set [high score v] to [score v]
            ask [High score! What is your name?] and wait
            set [name v] to (answer)
        end
        stop [all v]
    end

You’ll need to add this new code to the other 3 buttons too! Have you noticed that the ‘Game over’ code in each of the 4 buttons is exactly the same?

If ever you need to change any of this code, such as adding a sound or changing the ‘Game over!’ message, you’d have to change it 4 times! That could get annoying, and waste a lot of time.

Instead, you can define your own blocks, and reuse them in your project! To do this, click more blocks, and then ‘Make a block’. Call this new block ‘Game over’.

Add the code from the else block from the red button to the new block that appears:

You’ve now made a new function called Game over, which you can use anywhere you like. Drag your new Game over block onto the 4 scripts for the buttons.

Now add a sound for when the wrong button is pressed. You only need to add this code once in the Game over block that you made, and not 4 separate times!