Using Scratch 3, you will create an interactive game where you need to help Marty catch their favourite snacks that are falling from the sky to earn points. There are also some snacks falling from the sky that Marty doesn't like so we need to avoid them!

After completing this activity, you could then add your own twists to the game to make it harder or more challenging for players.

Using sensing blocks to work out what characters on the stage are touching

Coding variables to keep track of a score

Logical if statements to help us make decisions during the game

This activity introduces some key concepts of programming that can also be found in our 

Before we start coding our game, we need to make sure that we set the scene with a Marty sprite on the stage.

Click the button below to open a brand new Scratch project, ready for coding.

You will notice that on the stage, there is currently a cat. We want our main character to be Marty and not Scratch cat so we need to remove them from the stage. To do this, click on the delete button as shown below,

Next, we want to add a new character (or 

 as it is called in Scratch). But we don't want to use one of the options that Scratch have already built in. We want to upload our own character image to be used. Download and save the image using the button below,

Great! Now we are ready to upload our image of Marty into our Scratch project as the main character.

To do this, we need to hover over the cat face icon and select the option to 

 as shown below. Then all that is left to do is select the Marty image wherever it is stored in your files.

You might notice that the Marty on the Scratch stage is a little big. Let's change that!

All you have to do is change the number in the 

 textbox. Try playing around with this number until you find a size that you think is sensible. We set ours to 30.

Hopefully you now have something that looks like this...

If we want Marty to be able to move side to side to catch the falling food, then we will need to code some movements.

When we click the left arrow key on our keyboard we want Marty to move left and when we click on the right arrow key on our keyboard we want Marty to move right.

Let's start with clicking on the right arrow key,

When you click on the right arrow key, Marty should now move along the screen to the right. We just need to add in some instructions to move left. But this time because we want to move in the opposite direction we will need to use the '

 sign so our character knows to move the other way.

: You can think of these numbers like a number line. As you go along the number line towards the positive numbers you go to the right and if you go towards the negative numbers you move along the left!

Challenge: coding marty to move faster or slower

We now have Marty moving from side to side, ready to catch some food. But how could we change our code to make Marty move faster or slower?

All we need to do to change the speed that Marty moves across our screen is change the number in our blue 

Try changing the number 10 to a bigger number. What happens? Hopefully, you will notice that Marty moves across the screen in bigger 

Now try and change that number to something less than 10. Marty is now taking smaller steps so is moving slower than before.

Play around with this number and decide what speed you want Marty to move!

Our game is starting to take shape, the next step is to add in some snacks for Marty to try and catch!

The first snack we are going to add into our game is something that Marty likes. For this, we are going to add in some bananas for Marty to catch but you can pick what you think Marty's favourite snack would be!

To add in our bananas, we just need to add in a new sprite using the 

Don't forget to re-size the new sprite that you add in! You should have something like below,

The bananas are going to randomly drop from different parts of the sky on our stage. To do this we need to think about 

 and where the bananas will be on the screen. Take a look at this block,

This block will tell a sprite to go to different parts of the stage based on the coordinates that we give it. The very middle of the stage will have the coordinates 0 for 

Try moving your sprite around on the stage and see how their 

After exploring how these coordinates work, we know roughly where the top of the stage is but how do we make sure the snack isn't dropped from the middle of the screen all the time?

 block will pick a random number between the numbers that we tell it. In here, we have included the most left position and most right position that we could drop the snack from. That means that the snack will randomly fall from different parts of the top of the screen.

You can use these numbers in your program too!

Lets put that together with a few other instruction blocks,

We want to hide the snack so that the player can't see where it goes until it is ready to start falling from the sky. We have also added in a short pause so that the snack doesn't always fall at the same time.

We have Marty's favourite snack appearing at random parts along the top of the screen so now we need to add in some coding blocks to see some food falling from the sky.

To code the food to start falling down the screen, we need to slowly decrease the 

 of the sprite. Using a loop, we want to keep doing this until the snack is either caught by Marty or reaches the bottom of the screen,

What happens if you change the number in the 

By putting together all of those instructions we get something that looks like,

loop so that the food will keep falling throughout the game and not just once!

What happens when marty catches the snack?

You might notice when you tested your game that when Marty catches the bananas, they disappear and go back to the top of the screen but it would be nice if there was some kind of noise that let us know we caught them!!

Before we play the sound, we need to double check that Marty has in fact caught the snack falling down the screen. We can use an if statement again to help us do this and if the two sprites are touching then we can play a fun sound to let the player know they have successfully caught that falling snack!

Here's what the instructions for our banana sprite look like now,

Make sure the new instructions to play a sound are inside of the forever loop

We now have one falling snack for Marty to catch but wouldn't it be fun to have another one? This time, lets add in a snack that Marty doesn't like so needs to try and avoid!

The first step is to add a new sprite to the stage like we did for the bananas. This time you need to pick something that Marty does not like. We decided to add a donut as the snack that Marty does not like!

Then the code for this new snack will be exactly that same as the code we put together for the bananas. Here's a reminder of what that looked like,

challenge: can you add in your own sound recording?

It would be pretty cool if we could change the sound that was played when we catch the food Marty doesn't like to be an annoying noise to let the player know they caught the wrong snack!

It is really easy to add in our own sounds to a Scratch project. You can even record your own voice and play it back in your game!

To do this, all you need to do is click on the arrow beside the sound block that we have in our program and click on the option to 

We now have an awesome game that lets the player help Marty catch their favourite snack and avoid the others falling from the sky! The final step is to keep a score.

To keep track of our score, we will need to use something called a 

. A variable is used in programming to remember something for us, in our case, we ill use it to store and remember the score in our game. Let's start off by creating a brand new variable called 

We then need to set the score to start off at 0. Let's add this code into the code blocks that we have for Marty,

Building a Game in Scratch

We're going to add four big, arcade-style buttons to Marty's head, and write a Python program that will make Marty record a simple sequence of movements that he'll then carry out!

Some of you (older folks) might remember the 

, which was actually the first programmable robot I encountered way back in primary school. This is a 

 like that, but we'll be building it for ourselves!

To do this, we're going to design and 3D print a new top-plate for our Marty that has holes to fit our buttons, add a Raspberry Pi Zero with a USB board that lets the Pi read the buttons, and then write a simple Python program to react to the button presses and store up a sequence of steps that Marty will then complete.

Using the Pi instead of Marty's GPIO pins means this project is completely self-contained - once it's done, you won't need a laptop or tablet to run it! It would be simpler to just use Marty's GPIO, but this way lets us use and learn about a few more advanced topics.

), or a Marty v1 (you'll need to use the older parts 

, and you'll need to work out how to fit it all together)

Some nice big Arcade-Style buttons, we've used 

 (£1.50 ea.) also from Pimoroni, but their whole 

 (£21) might be easier to use as it includes pre-made wires and some other cool bits

 (~£9.30) (other Pi variants may also work, but might be a tricky fit)

 that you don't mind cutting up and destroying!

A Soldering iron, some wire and some solder

Either a 3D Printer to print a new top-plate for your Marty V2, 

 some cardboard, tape and a sharp knife (Marty v1 users can 3D print a whole new front-face or resort to a big drill bit!)

I'm going to assume you've done a little bit of Python before, so know how to create programs and run them. If not, not to worry! Quickly run-through our 

An adult to supervise! Staying safe when using sharp and hot things is important.

Some basic TinkerCAD and 3D Printing skills

Some interesting things we can do in Python with libraries, lists and loops

Using Pythonwith hardware on a Raspberry Pi

Some soldering, if you haven't done it before!

The first thing we need to do is work out how we're going to add the buttons to our Marty. The new 

has easily changeable top-plates and face-plates, so we're going to design a new top that has holes for four of our arcade buttons. Luckily these buttons just clip in, so there's no need to used screws or glue to hold them in place.

If you're using a Marty V1, start with the 

If you don't have access to a 3D printer, that's no problem - with some scrap cardboard, you can still make a top plate that fits snugly and will work just as well.

First thing's first, we need to start from something! Click below to download a STL file of the blank top-plate, that we'll modify using TinkerCAD, a simple and free to use CAD software (If you already know how to use another CAD package, you can use that instead if it can read STL files).

Sign up at the above TinkerCAD link. If you've never used TinkerCAD before, I'd recommend following through the beginner tutorial it'll offer you. It only takes about 5 minutes to complete and nicely introduces TinkerCAD's features.

 to our TinkerCAD file if you want to compare)

Now we're going to create a project for our top plate. From the 

TinkerCAD will generate a random name for you, in the top left -- let's change it to somethin sensible, like "Button Head" by clicking the name, typing a new name and then hitting 

Next, you need to import the starter blank Top-Plate template, which you downloaded in the last step.

 button in the top right of the screen, then select the file you just downloaded. It'll take a second or two to import.

Next, we want to select the plate, and flip it upside-down so the top surface is now on the underside. I also rotated it 90 degrees to the left, and changed the colour to Yellow.

Now, we need to punch four big holes in this top-plate.

Take care to measure the width of your physical buttons, with a ruler or calipers if you have them. Ours were about 30 mm in diameter, so we'll make the holes a tad larger at 31 mm so that its not too-tight a fit - remember that 3D printers often make holes slightly smaller and pegs slightly larger.

 menu on the right, and place it somewhere on the flat portion of the plate.

Now we need to scale the hole so it's the right size - click the white square handle on the horizontal plane, and drag it until the X and Y dimensions show 31 mm each.

It's a good idea to also check that the size of the top plate in your model is the same size as a real plate, which measures 

 67 mm x 117 mm. You shouldn't need to resize it.

Once you've got one hole the right size, you can use the 

The arrangement I've gone for is shown below, the corner button holes are just placed by eye, making sure they don't hit the walls. The two inner holes are placed 47 mm to the side of the corner holes.

The last step is to select all four holes 

 which will, after a second, leave you with a top plate with four big holes!

. Import it into the slicer you normally use with your printer, and get it printing!

, clicking on the project's icon and then the big 

Here's our top plate if you want to check it against yours or just print it instead: 

Pre-Made Top Plate with Button Holes STL Download

As mentioned earlier, you can also use cardboard to assemble a top-plate that fits snuggly - here's an example one we made quickly using a box cutter, an old Amazon box, a pair of compasses and some double-sided tape to stick two sheets together to thicken the plate up and give it a lip to slot in:

Now that we have our Top Plate, we need to fit the buttons and wire in the Raspberry Pi and Player X controller.

Pop four buttons in to the plastic part we just 3D printed:


Flip it over, and add wires to each of the tabs on the buttons.

I've used cut-down cables provided in the Pimoroni Arcade parts kit that have pins on one end and a connector that fits the tabs on the other, but soldering wire straight on to the tabs will also work (single-stranded solid-core wire would be easiest to use here).

I'd also recommend putting some electrical tape over the tabs to prevent any accidental shorting later.

Now we're going to ge the Raspbery Pi and Player X controller working together.

I'll assume you've get Raspbian running on the Pi already. To check it works together, plug the Player X in to the Pi using the Micro USB cable, using a hub or OTG adapter as you usually would to plug stuff in to a Zero. The 

 is a good choice, as it has an integrated hub.

Set up SSH or VNC and a network connection so you can still access the Pi when it's installed inside Marty's head.

A white light should come on when the Player X is plugged in. From the console (Terminal) on the Pi, type the following, then hit enter:

 which lets us know the system has identified the board. If you don't see anything, check your connections and try a different USB cable. After soldering everything together later, this is a good sanity check to run again if it's not working for you.

Make sure the Player X and Pi are now powered-off so we can solder our stuff together.

We're going to cut-up and solder a USB cable directly on to the Pi Zero, to make it as small as possible so it fits inside Marty's head!

Carefully cut the bigger USB-A end of the cable off, leaving yourself about 10 cm of slack on the Micro B end.

Next, remove the outer insulating layer on the cable, taking care not to cut in to the four smaller wires inside the cable, so you're left with a plug and four loose wires coming out the end of it (You can see what I mean in the image below).

The Pi Zero has some circular golden pads on its underside, which we can get the four USB signals from: +5 V, Ground, D+ and D-.

In a USB cable, +5 V is red, GND is black, D+ is green and D- is white.

Solder the USB wires on to these pads, note that you can also get +5V and GND from the Pi's GPIO header (

I also found the Player X worked well stuck to the back of the Pi - just make sure its well insulated, with a layer of electrical tape between the two.

 notice I got the D+ and D- the wrong way around there - D'oh! I fixed it after getting the picture. I also found the circular pads to be more reliable for powering the Player X than the GPIO pins.

As we've soldered to the Pi Zero's USB port, we now can't plug anything in whilst the Player X is plugged in, as USB doesn't allow multiple connections without a hub. If you do need to plug a keyboard or whatever in, just gently unplug the Player X.

Plug the four buttons in the the Player X. I found that buttons number 1, 2, 4 and 5 were the SOUTH, EAST, NORTH and WEST gamepad codes, so I used them. As thay're just dumb switches, it doesn't matter which way around they go (polarity).

Lastly, plug the Pi in to Marty using the standard Pi connection cable.

Now we can power up Marty and the Pi together!

SSH or VNC in to the Pi, whichever you prefer, and we'll get started on the Python code...

To use the Player X from Python, we'll use the wonderful 

 like a game controller or keyboard andlet you react to and code with each button or key press it gets.

I'll assume you're happy setting up a simple Python project, if not check out our 

I'd recommend installing iPython as it's a great interactive way to play with your Python program as it's running. Start 

 in a console, and import the inputs library.

Button-Head Marty

Change the Argument

Check Learning - Unplugged Sequences

Check Learning - Variables

On the front and bottom of Marty's feet there are some special sensors that help Marty sense different obstacles around them. In this activity we will show you how to use the sensors on the bottom of the feet to stop your Marty from walking off the edge of a table, or accidentally taking a stage dive!

A device with our Marty the Robot v2 app downloaded and up to date

Through example code, this activity presents an example of how to use the sensors on the bottom of the feet to sense when Marty is about to fall off a table or object!

Open up the Marty the Robot v2 app and follow the instructions there to connect your robot to the app. Then click on 

 to open a new Scratch project ready for coding,

 to check if Marty's foot is still on the ground.

 block allows you to read the current state of the sensor that is checking if the foot is on the ground. By assigning what the 

) will read true when the Marty's foot is on the ground and false when Marty's foot is not on the ground. Set 

You need this short section of code to run at the same time as other code that you write to control Marty.

 variable to detect whether Marty’s foot is touching the ground.

At the end of each step Marty takes, we can check the sensor again to see if the foot is still on the ground or not. If Marty's foot is on the ground then the 

However, if Marty is about to step into thin air 

 will read false, indicating Marty has come to an edge. When this happens Marty will no longer take any more steps forward and instead will look angry!

Start both sections of code by clicking on the 

Once Marty has detected the danger of being about to step off an edge it would be useful if Marty reacted appropriately rather than just looking angry!

Make the code below . This will program Marty to 

 around when encountering an edge. The outer 

 allows Marty to walk to an edge 4 times before giving up! And there are appropriate Marty eye movements of course... 

You have written many activities worth of code now so will be becoming an expert in Scratch. Try to work out and explain what each part of the code does. You could try making Marty do different moves when getting to the edge - just keep a hand ready to catch Marty if it goes a bit wrong!

So far we have thought about Marty losing contact with the ground by stepping off an edge into thin air. Another way that Marty could lose contact with the ground is if Marty is lifted up. Can you set an alarm so that if someone picks Marty up and tries to take Marty away they will get a big surprise?!

Code a routine so that if Marty's feet lose contact with the ground, an alarm sounds! Here are a few things you will need to think about,

What is Marty going to be doing until picked up? Standing still? Going round in circles?

What sort of noise do you want for your alarm? 

Will anything else happen when Marty is picked up?

Here is our example alarm. We used the same idea as the code used in the activity - a 

 containing instructions for how Marty should move until the sensor tells us that Marty's foot is no longer on the ground. We have Marty doing a little dance to pass the time!

We keep repeating this dance until Marty's foot is lifted off the ground and the sensor returns 

We have chosen to add a funny sound using a 

 block if Marty has been picked up. We have set this noise to repeat a few times using the 

You have now just programmed Marty to react if the sensors on the bottom of the feet tell us that Marty has lost contact with the ground. If you want to continue to explore this idea, here are a few ideas!

How can you prevent Marty stepping off a platform when walking sideways?

What about stopping Marty walking off a table backwards?

Going Over the Edge

Guided By the Light

How Marty behaves, and how to care for your Marty

How to connect to Marty from Scratch, and program sequences of movements!

How to change parameters to change Marty's behaviour

This tutorial walks students through the basics of how to use Marty, but also introduces the concepts of 

You’ve now got a robot friend for life!

But, there are several things you should know about caring for your Marty, to ensure a long and happy relationship.

Before you start, make sure you've been through our

Marty's on switch can be found on the back along with some useful lights to let you know if Marty is already connected to a device or if Marty needs to be charged.

You can check the getting started guide that came with Marty to remind yourself what the different lights mean!

A charging cable came with your Marty, that you can use to charge from a USB port. A flashing blue light will turn on whilst Marty is charging and will turn into a solid blue light once Marty is fully charged.

Marty can be used while charging, but don't leave it turned on and plugged in or the charger will eventually deactivate, and then Marty will just run out of battery

When Marty's battery starts to run low, the lights on the back will begin to turn from green to red as you start to run out of charge.

You've probably already tried out the Scratch programming language. If not, don't worry - getting started with Marty using Scratch is super easy!

Ok! Now we're connected to Marty and ready to program!

One quick rule - always start your code with a "Get Ready" coding block, to make sure Marty is standing up straight with all the motors are turned on so we are ready to start moving. If your Marty stops moving - ask them to Get Ready!

In Scratch, click together the "When green flag clicked" from the 

 section, and the "get ready" block from the 

Then, click the green flag to run your code

Learning Portal