1. Creating Games with Greenfoot
Overall time on activity: 30 minutes
Wombats
Creating Games with Greenfoot

2. What is Greenfoot?
A free environment that makes it easy to create 2D animations, simulations, and games

3. Getting Started To start Greenfoot click on Greenfoot.
2 mins
Getting Started
To start Greenfoot click on Greenfoot.
Click on “Scenario” in the menu
Choose Open
Pick the wombats scenario
It starts by showing an empty WombatWorld
Which is a 2D grid of cells

4. Adding Objects to the World
3 mins
Adding Objects to the World
Right click on Wombat in the class display to see a pop-up menu
Create a Wombat by selecting
new Wombat()
A picture of a wombat will appear attached to the cursor
Click in the world to place the wombat
Shift-click to place more than one object
Class
Display

5. Add Leaves Add several leaves to the world
1 mins
Add Leaves
Add several leaves to the world
Right click on Leaf in the class display
Quickest: Hold down the shift key
Click in the grid to place each leaf

6. Greenfoot Objects There are two basic types of things in Greenfoot
Worlds and actors.
Worlds hold actors
a stage for actors
Actors can act
They may move
They may eat food
They may stay where they are

7. Run the Simulation Click on act to execute one simulation time step
4 mins
Run the Simulation
Click on act to execute one simulation time step
Act one time
Click on run to have it continuously execute time steps
Keep acting till you
Click on pause to stop
Click on reset to start over
With a new WombatWorld
Execution Controls

8. What Happened? Questions
How did the wombats move?
Did they eat any leaves?
Did the leaves move?
What happened when a wombat reached the edge of the world?
If you don’t know the answer to any of these questions place more wombats and/or leaves in the world and run again
Or click on act to see things in slow motion

9. The Wombat Scenario To get information on any scenario
Click on the Project Information button
In top right corner above the class display
Read the displayed documentation
Click close when done

10. Actor Methods
You can see and execute all methods that an actor knows how to do
By right clicking on an actor in the grid
Select a method to execute it
You can call some other methods as well

11. Method Return type
The words before the methods define the return type of a method.
If the behavior is about changing the state of the object, the return type will be “void” which means it is telling the object to do something.
The other is a non-void type which is asking the object a question.
And specifies what the return type will be.
A method with a void return type does not return a value. A non-void method returns a value.

12. Return Types
non-void return a value.

13. Exercises 8 mins Call out the canMove( ) method on your wombat.
Does it always return true? Or can you find situations in which it returns false?
Using a newly created wombat, the getLeavesEaten ( ) method will always return zero.
Can you create a situation in which the result of this method is not zero?
Call out the setDirection (int direction) method.
Provide a parameter value and see what happens.
Which number corresponds to which direction?
Write them down.
What happens when you type in a number greater than 3?
What happens if you provide input that is not a whole number, such as a decimal number (2.5) or a word (three)?

14. World Methods Right click near the title of the world
To show the world menu
Select populate()
This will add wombats and leaves to the world
Then click on run
What happens?
Do all the leaves get eaten?

15. Changing Actors Changing Actors Right click on the actor’s class
Choose “Set Image”
Choose the image from the library
Compile the program

16. What I have learnt this lesson:
Scratch and Greenfoot share some themes:
Sprite = Actor, Stage = World
Greenfoot scenarios consist of classes
Many Objects can be created from a class
The return type of a method specifies what a method will return
Methods with non-void return type represent questions; Methods with void return types represent commands.
Collaborate, be creative and pursue the a solution.