Page 71 - Learn To Program With Scratch

ClickOnFace .sb2 If you want people to interact with a sprite, you could change its cos-
tume in response to a mouse click, as in the Click on Face application.
This application contains a single sprite, named Face, which has the five cos-
tumes shown in Figure 3-2. It uses the when this sprite clicked block (from
the Events palette) to tell the sprite when to switch costumes.

 The five costumes of the Face sprite
 Tell the Stage to change its backdrop.

The four backdrops of the Stage
 When the Stage switches to Stage4, glide to
the upper-right corner and back to the center.
Figure 3-2: The smiley face and the backdrop change whenever the sprite is clicked .

When you run this application, every time you click the mouse on the
face image, the image will change to the next one in the list. The script
also uses the switch backdrop to block to command the Stage to switch
randomly to one of its four backdrops. When the Stage switches to its
Stage4 image, the Face sprite detects this event (using the when backdrop
switches to trigger block from the Events palette). In this case, the face
makes a trip to the upper-right corner of the Stage and then returns to
the center.

try it out 3-1
TrafficLight .sb2 The file TrafficLight.sb2 contains one sprite that has three costumes (named red,
orange, and green) and an incomplete script, as shown below . Complete the
application by adding the necessary wait blocks to create a realistic traffic light
animation .

red orange green

Looks and Sound 49

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