Page 167 - Learn To Program With Scratch

When a button is pressed, its sprite moves a little bit down and to the
right to give the visual effect of a button press. When the mouse is released,
the sprite returns to its original position and sets the value of the variable
choice to indicate that the user clicked that button. Note that each sprite
sets choice to a different number. The blocks for moving the buttons in
these scripts are not strictly necessary and can be removed if desired.
Once the user chooses a triangle type, choice becomes greater than zero,
and the main script calls the CheckAnswer procedure. This procedure com-
pares the type variable (which specified the type of the drawn triangle) with
the value of the choice variable. If the two variables have the same value,
then the user’s answer was correct. Otherwise, the user’s answer was wrong,
and the script will say the correct classification.

try it out 6-2
Open this game and play it a few times . Once you understand how it works, try
adding some extra functions . Here are a few ideas:
• Make the game keep score . It could add a point for each correct answer and
deduct a point for each incorrect answer .
• Give the user an option to quit the game .
• Define a criterion for ending the game . For example, you could set the main
repeat loop to run 20 times instead of forever . You could also stop the game
after five incorrect answers .
• Have something exciting happen while the game is running . For example,
you might create a variable named specialNumber and assign it a random
value at the start of the game . When the number of correct answers matches
specialNumber, the game could give the user bonus points, play music, or
even tell a joke .
• Bring the buttons to life with graphics effects . For example, if you add the
script shown below to each button, the buttons will change color when the
mouse hovers over them .

Making Decisions 145

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