Steps to open a scenario in Greenfoot:

1. Double-click the Greenfoot icon to launch Greenfoot.
2. Locate the folder on your computer where you store your Greenfoot scenarios. Select the scenario, then click Open.
3. The scenario will open in a new window.

Using Scratch to make an object move

1. Use the point in direction angle command and the move number steps number command to move an object in Scratch.
2. Use the change x by number command to move an object horizontally in Scratch.
3. Use the change y by number command to move an object vertically in Scratch.

Programming in Greenfoot at its most basic consists of subclassing two built-in classes, World and Actor. An instance of the world subclass represents the world in which Greenfoot execution will occur. Actor subclasses are objects that can exist and act in the world.

The parameter has limited scope. It is similar to a local variable, in that is exists only for the duration of the execution of the method. Once the method is exited from (a return is executed or the end of the method is reached), the variable no longer exists.

Click the ‘Act’ button in the execution controls. Each object now acts — that is: each object does whatever it is programmed to do. In our example, leaves are programmed to do nothing, while wombats are programmed to move forward. Try placing two wombats into the world and press Act again.

You can use two values top and left along with the position property to move an HTML element anywhere in the HTML document.

1. Move Left – Use a negative value for left.
2. Move Right – Use a positive value for left.
3. Move Up – Use a negative value for top.
4. Move Down – Use a positive value for top.

If you want the sprite to move, then use the following code: When green flag clicked forever if up arrow pressed change y by 10, if right arrow pressed change x by 10, if left arrow pressed change x by -10, and if down arrow pressed change y by -10. [If you want it to go faster or slower, change the numbers in code.]

Here’s the code: We use the Greenfoot built-in methods for checking if a key is down. Between the quotes is the name of the key, “left” is the left cursor key, “right” is right. If you want something like “a” and “d”, just use those instead! Our code is saying: if those keys are down, turn a certain number of degrees.

You need to precisely match what is written there. It’s the word move, followed by round brackets containing the number 4, followed by a semi-colon.

The crabs aren’t actually stopping as such; they are still trying to move, but Greenfoot doesn’t let them move out of the world (if they did, how would you drag them back in again?). You can vary the speed of the Crab by changing the number 4 in the code to a different number.

Note: The wombat will still have to turn left if it hits a wall before taking 5 steps. Whenever the Wombat hits a wall, reset the number of steps to zero. Hint: Most of your modifications to this class should go in the act () method.