Moving Things Around
Right now your parrot moves in a circle, but wouldn’t it be more fun to control it with the arrow keys? In this step, you’re going learn how to do that!
Start by deleting any code that you have for the parrot.
As you’ve probably guessed, you’re going to need event and motion blocks again!
This time, look for this block and drag it onto the current sprite panel:
Click the little arrow (▼) beside space. You will see a list of all the keys on your keyboard that you can pick from.
You’re going to need four of these blocks and you can connect them to motion blocks like this:
Note: -10 means ‘go back 10 steps’.
Now click the green flag and press the arrow keys to test your code.
Your parrot moves back and forwards now, which is pretty cool, but it doesn’t move up or down. Also, if you look through the motion blocks, you’ll see there are no blocks for ‘up’ or ‘down’. There are a whole bunch of them related to x and y though — let’s try those!
Grab two change y by blocks and update your code like this:
Now when the arrows are pressed, the parrot can move all over the stage!
How do x- and y-coordinates work?
When programmers need to talk about the positions of objects, like sprites, we often use x and y coordinates to describe them. The x-axis runs from left to right, while the y-axis runs from bottom to top.
A sprite can be located by the coordinates of its centre, written for example like (15, -27), where 15 is the position along the x-axis position, and -27 the position along the y-axis.
- To try out how this works, select a sprite and set different values for its
xandycoordinates to move the sprite around the Stage.
- Try different pairs values to see where the sprite goes! In Scratch, the x-axis goes from
-240to240, and the y-axis goes from-180to180.
Restarting the game
The parrot moves all over the screen, but imagine this is a game: how do you restart it? You need to get the parrot back to its original location when the player starts the game. They’ll start this game by clicking on the green flag, so you need to change the parrot’s x and y coordinates when that happens.
That’s actually pretty easy! The centre of the stage is (0,0) in x and y coordinates.
So all you need is an event block for that green flag and the go to block from motion.
Drag the when green flag clicked event block onto the current sprite panel.
Then find the go to motion block and snap it on to your flag event block.
Set both the x and the y to 0 in the go to block if they are not already 0.
Now click the green flag, and you should see the parrot return to the centre of the stage.