Projects
Dodgeball
Create a platform game in which you dodge moving
balls to reach the end of the level
Step 1 Introduction
You’ll learn how to create a platform game in which the player has to dodge moving balls to reach the end of the
level.
What you will need
Hardware
A computer capable of running Scratch 3
Software
Scratch 3 (either online (https://scratch.mit.edu/projects/editor/) or offline (https://scratch.mit.edu/d
ownload/))
Downloads
You can find the downloads here (https://rpf.io/p/en/dodgeball-go).
What you will learn
How to use the keyboard to control a sprite
How to use the if, then, else Scratch block
How to clone a sprite
Additional notes for educators
You can find the completed project here (https://rpf.io/p/en/dodgeball-get).
Step 2 Character movement
Start by creating a character that can move left and right, and can climb up ladders.
Open the ‘Dodgeball’ Scratch starter project.
Online: open the starter project at rpf.io/dodgeball-on (https://rpf.io/dodgeball-on).
If you have a Scratch account you can make a copy by clicking Remix.
Offline: download the starter project from rpf.io/p/en/dodgeball-get (https://rpf.io/p/en/dodgeball-
get) and then open it using the offline editor.
The project contains a backdrop with platforms:
Choose a new sprite as the character the player will control, and add it to your project. It’s best if you
choose a sprite with multiple costumes, so that you can make it look as though it’s walking.
Add a sprite from the Sprite Library
Click on Choose a Sprite to open the Sprite Library:
You can search for a sprite, or browse for one by category. Click on a sprite to add it to your project.
Add code blocks to your character sprite so that the player can use the arrow keys to move the character
around. When the player presses the right arrow, the character should point right, move a few steps, and
change to the next costume:
when clicked
forever
if key right arrow pressed? then
point in direction 90
move 3 steps
next costume
If your sprite doesn’t fit, adjust its size.
Test out your character by clicking the flag and then holding down the right arrow key. Does your
character move to the right? Does your character look like it is walking?
Add code blocks to the character sprite’s forever loop so that it walks left if the left arrow key is
pressed.
I need a hint
Your code should look like this now:
when clicked
forever
if key right arrow pressed? then
point in direction 90
move 3 steps
next costume
if key left arrow pressed? then
point in direction -90
move 3 steps
next costume
Test your new code to make sure that it works. Does your character turn upside-down when walking to
the left?
If so, you can fix this by clicking on the direction of your character sprite, and then clicking on the left-
right arrow.
Or if you prefer, you can also fix the problem by adding this block to the start of your character’s script:
set rotation style left-right
To climb a pink ladder, your character sprite should move a few steps upwards on the Stage whenever
the up arrow is pressed and the character is touching the correct colour.
Add inside your character’s forever loop to change the character’s y (vertical) position if the up
arrow is pressed and the character is touching the colour pink.
if key up arrow pressed? and touching color ? then
change y by 4
Test your code. Can you make the character climb the pink ladders and get to the end of the level?
Challenge!
Challenge: completing the level
Can you add more code blocks to your character sprite to make the sprite say something if it gets to the green
door?
Step 3 Gravity and jumping
Now you’re going to make your character move more realistically: you’re going to add gravity to your game and give
the character the ability to jump.
In the game, move your character so that it walks off a platform. Do you see that it can walk into empty
space?
To fix this, add gravity to your game. To do this, create a new variable called gravity.
Add a variable in Scratch
Click on Variables in the Code tab, then click on Make a Variable.
Type in the name of your variable. You can choose whether you would like your variable to be
available to all sprites, or to only this sprite. Press OK.
Once you have created the variable, it will be displayed on the Stage, or you can untick the
variable in the Scripts tab to hide it.
You can hide this variable from your Stage if you want to.
Add these new code blocks that set gravity to a negative number and use the value of gravity to
repeatedly change your character’s y-coordinate:
when clicked
set gravity to -4
forever
change y by gravity
Click the flag, and then drag your character to the top of the Stage. What happens? Does the gravity
work as you expect?
Gravity shouldn’t move the character sprite through a platform or a ladder! Add an if block to your code
to only let the gravity work when the character is in mid-air. The gravity code should then look like this:
when clicked
set gravity to -4
forever
if not touching color ? or touching color ? then
change y by gravity
Test the game again to see whether gravity works correctly now. Does your character sprite stop falling
when it touches a platform or a ladder? Can you make the character walk off the edge of platforms and
fall onto the level below?
Now add code to make your character jump whenever the player presses the space key. One very easy
way to do this is to move your character up a few times:
when space key pressed
repeat 10
change y by 4
Because gravity is constantly pushing your character down by 4 pixels, you need to choose a number
greater than 4 in your change y by (4) block. Change the number until you’re happy with the height
the character jumps.
Test out your code. Notice that the jumping movement isn’t very smooth. To make jumping look
smoother, you need to move your character sprite by smaller and smaller amounts, until it is not rising
any higher.
To do this, create a new variable called jump height. Again, you can hide this variable if you prefer.
Delete the jumping code you added to your character sprite, and add this code instead:
when space key pressed
set jump height to 8
repeat until jump height = 0
change y by jump height
change jump height by -0.5
This code moves your character up by 8 pixels, then 7.5 pixels, then 7 pixels, and so on, until it does not
rise any higher. This makes jumping look much smoother.
Change the value of the jump height variable that is set before the repeat starts. Then test your
game.
Repeat these two steps until you’re happy with how high the character jumps.
Challenge!
Challenge: better jumping
Even if the character is already in mid-air, it jumps whenever the player presses the space bar. You can see this
behaviour if you hold down the space bar.
Can you change the character sprite’s code for jumping so that your character can only jump if it touches a blue
platform?
Step 4 Dodging balls
Your character can move and jump now, so it’s time to add some balls that the character has to avoid.
Create a new ball sprite. You can choose any type of ball you like.
Resize the ball sprite so that the character can jump over it. Try making the character jump over the ball
to test whether the ball is the right size.
Add this code to your ball sprite:
when clicked
hide
forever
wait 3 seconds
create clone of myself
when I start as a clone
go to x: 160 y: 160
show
repeat 22
change y by -4
repeat 170
change x by -2
turn 6 degrees
repeat 30
change y by -4
delete this clone
This code creates a new clone of the ball sprite every three seconds. Each new clone moves along the
top platform and then drops.
Click the flag to test the game.
Add more code to your ball sprite so that clones of it move across all three platforms.
I need a hint
The code for your ball sprite clones should look like this:
when I start as a clone
go to x: 160 y: 160
show
repeat 22
change y by -4
repeat 170
change x by -2
turn 6 degrees
repeat 30
change y by -4
repeat 180
change x by 2
turn 6 degrees
repeat 30
change y by -4
repeat 170
change x by -2
turn 6 degrees
g
Now add some code blocks to broadcast (send) a message if your character gets hit by a ball!
delete this clone
Add this code to your ball sprite:
when I start as a clone
forever
if touching Pico walking ? then
broadcast hit
Finally, add code blocks to your character sprite to make it move back to its starting position when it
receives the hit message:
when I receive hit
point in direction 90
go to x: -210 y: -120
Test out your code. Check whether the character moves back to the start after touching a ball.
Challenge!
Challenge: random balls
The balls that your character has to dodge all look the same, and they appear at regular three-second intervals.
Can you add code to your game so that the balls:
Don’t all look the same?
Appear after a random amount of time?
Are a random size?
Step 5 Lasers!
To your game a little harder to complete, you are going to add lasers!
Add a new sprite to your game and call it laser. It should have two costumes: one called ‘on’, and one
called ‘off’.
Place your new laser sprite between two platforms.
Add code to your laser sprite to make it switch between its two costumes.
when clicked
forever
switch costume to on
wait 2 seconds
switch costume to off
wait 2 seconds
If you prefer, you can change the code shown above so that the sprite waits a random amount of time
between costume changes.
Finally, add code to your laser sprite so that the laser sprite broadcasts a ‘hit’ message when it touches
the character sprite.
I need a hint
This is the code you should add:
when clicked
forever
if touching Pico walking ? then
broadcast hit
You don’t need to add any extra code to your characters sprite, because the character sprite already
knows what to do when it receives the broadcast 'hit'!
Test out your game to see if you can move the character past the laser. If the laser is too easy or too hard
to avoid, change the wait times in the code for the laser sprite.
Challenge!
Challenge: more obstacles
If you think your game is still too easy, you can add more obstacles to it. The obstacles can be anything you like!
Here are some ideas:
A dangerous butterfly
Platforms that appear and disappear
Falling tennis balls that must be avoided
You could even design another backdrop to create the next level. Then add code so that, when your character
reaches the green door, the game switches to the new background:
if touching color ? then
switch backdrop to next backdrop
go to x: -210 y: -120
wait 1 seconds
Challenge!
Challenge: improved gravity
There’s one other small bug in your game: gravity doesn’t pull the character sprite downwards if any part of the
sprite is touching a blue platform. So even if the sprites head touches a platform, the sprite doesn’t fall! You can
test this yourself: make your character climb most of the way up a ladder, and then move the character sideways
beneath a platform:
To fix the bug, you first need to give your character sprite new trousers that have a different colour (on all
costumes).
Then replace this code block:
touching color ?
with this code block:
color is touching ?
To make sure you’ve fixed the bug, test the game after you’ve made these changes!
Challenge!
Challenge: more lives
Right now, your character goes back to its starting position when it gets hit. Can you also give the character
sprite three lives, and make it lose one life when it gets hit? Here’s how your game could work:
The game starts with three lives for the character
Whenever the character gets hit, it loses one life and moves back to the start
If there are no lives left, the game ends
Step 6 What next?
Have a go at our Brain game (https://projects.raspberrypi.org/en/projects/brain-game?utm_source=pathw
ay&utm_medium=whatnext&utm_campaign=projects) project, in which you can create your own maths quiz.
Published by Raspberry Pi Foundation (https://www.raspberrypi.org) under a Creative Commons
license (https://creativecommons.org/licenses/by-sa/4.0/).
View project & license on GitHub (https://github.com/RaspberryPiLearning/dodgeball)
