Page 58 - Learn To Program With Scratch

Scratch Projects
In this section, we’ll develop two short programs that should further
your understanding of the Motion and Pen blocks you’ve learned so
far. You can find the backdrops and sprites in the project files for this
chapter, so we’ll focus on writing the scripts we need to make these
applications work. An explanation of an additional bonus game, called
Survival Jump, is available in the extra resources. You’ll find details in
BonusApplications.pdf (http://nostarch.com/learnscratch/).
Some of these scripts will use command blocks that you haven’t seen,
but don’t worry if you don’t completely understand some things. You’ll
learn all about them in the coming chapters.

Get the Money
Money_ Our first application is a simple game in which the player needs to move
NoCode .sb2 the sprite by using the keyboard arrows to collect as many bags of gold
as possible. As illustrated in Figure 2-16, the bag of gold appears at a
random location on the grid. If the player doesn’t grab the bag in three
seconds, it moves somewhere else.

150 The Stage’s backdrop
This sprite, named Gold, will
90 appear at random locations
on the grid.
30
Move this sprite, named
Player, using the arrow keys
–30 to catch the bag of gold. You
have only three seconds to
get to the bag.
–90
Every time you catch a bag,
your score will increase by 1.
–150
–210 –150 –90 –30 30 60 90 210

Figure 2-16: Help the cat grab as many bags of gold as possible!

Open the file Money_NoCode.sb2. The scripts are missing, but you’ll
create them now, and the file contains everything else you’ll need.

n o t e The coordinate axes shown in Figure 2-16 were added to help you understand the
numbers used in these scripts. Come back to this figure as needed to refresh your
mental picture of how the sprites are moving.

Let’s start by writing the scripts for the Player sprite, as shown in
Figure 2-17.

36 Chapter 2
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