Page 75 - Learn To Program With Scratch

If you want the girl to be behind the rock, you must bring the rock to
the front drawing layer or send the girl to the back drawing layer. Scratch
provides two commands that allow you to reorder the drawing layers, go to
front and go back layers (also shown in the figure). The first tells Scratch
to always draw a sprite on top, while the second sends a sprite back as many
layers as you specify.

try it out 3-4
Layers .sb2 The Layers.sb2 application has four objects that move on the Stage . You can bring
an object to the top by pressing the first letter of its color . Run the application to
explore the effect of the go to front command .

We’ve covered animation with the Looks palette, but there’s another
thing that can liven up our applications. In the next section, we’ll explore
the Sound palette and its rich set of commands.

the Sound Palette

Games and other applications use sound effects and background music to
add excitement. In this section, you’ll learn to use Scratch’s sound-related
blocks, starting with how to incorporate audio files and control their play-
back. You’ll then look at command blocks for playing drums and other
musical instruments. After that, you’ll find out how to control the volume
and change the speed (or tempo) at which musical notes and drums are
played.

Playing Audio Files
You can save audio files on your computer in many formats, but Scratch
only recognizes two: WAV and MP3. There are three command blocks that
allow you to use these sound files in your applications: play sound, play
sound until done, and stop all sounds. Both of the first two blocks play
a given sound. The play sound command lets the next command start
before the sound finishes playing, while play sound until done won’t move
on to the next command until the end of the sound. The stop all sounds
command immediately turns off any sound that is playing.
You can add background music to your application by playing an
audio file repeatedly. The easiest way to do this is to use play sound until
done to let the file to play completely, and then restart it, as shown in
Figure 3-7 (left).

Looks and Sound 53

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