Operation Manual

Example 2: Animation and Sound
While Hello World is a very traditional example, it’s not particularly interesting. It also fails to show off the true power of
Scratch, which lies in its impressive multimedia capabilities and sprite-handling system. This system is particularly well suited to
simple animations, which can form the basis of an interactive game.
To begin, start a new project in Scratch by either loading the program afresh or choosing New from the File menu. As with any
starter project, Scratch will provide a default sprite—it’s this sprite that you will be controlling.
To control a simple animation in Scratch, you use the Motion section of the blocks palette. When you start a new project, this is
the default palette. Drag the block labelled move 10 steps to the Scripts area. As its name suggests, this block tells the
selected sprite to move 10 steps in the direction it is currently facing. The default sprite in Scratch is always started facing directly
to the right—thus, the move 10 steps block will move the sprite 10 steps to the right.
Ten steps isn’t a very large value, so click on the value 10 and change it to 30. The block should then read move 30 steps. An
animation of a cat moving to the right of the stage isn’t that interesting, however, so switch to the Sound block palette and drag
the play sound meow block to the Scripts area and link it beneath the existing move block. To keep the cat in this position for
a while, add in a wait 1 secs block from the Control block palette. Without this, the sprite will appear to flick quickly
between its starting position and the target position.
To make it so the program can be run multiple times without the cat sprite disappearing off the edge of the stage, add another
move 10 steps block beneath the play sound block and modify it to read move -30 steps. Scratch will happily allow you
to use negative figures like this: if a value of 30 makes the sprite move a certain distance to the right, -30 will make it move the
exact same distance in the opposite direction.
Finally, add the when [flag icon] clicked block from the Control block palette to the top of the Script area’s stack of
blocks to complete the program as shown in Figure 10-5. Clicking the green flag icon on the top-right of the screen will trigger
the program—make sure you’ve got speakers or headphones connected to the Pi for the full effect!
Figure 10-5: The completed animation program in Scratch