Learn to Program with Small Basic

1 step away). If the arrow hits the dragon, it’ll slay him instantly! With the
sword, the knight has a 50-50 chance of slaying the dragon (but only when
he’s close enough). If Good Knight slays Draggy, he’ll become Knight of the
Year, win his very own dance party, and get his picture on the castle wall.
Once Good Knight makes his move, Draggy breathes his flames at the
knight. If he hits the knight, he’ll weaken the knight’s shield. When the
shield loses its strength, the knight is defenseless. After this point, if the
dragon’s fire hits the knight, it’ll burninate him! The entire city will be
under the attack of the merciless, ferocious dragon. Game over!
The game uses five images that you can find in this chapter’s folder:
the background image (your battlefield), two images for the dragon (one
image shows the dragon’s fire), the knight’s image, and an image of an
arrow. Follow steps 1–10 to make a fun dragon game!
Step 1: Open the Startup File
Open the Dragon_Incomplete.sb file from the code folder for this chapter.
This file contains the code in Listing 10-7 and has empty placeholders for
your subroutines. You’ll add the code for these subroutines one step at a
time. The program’s folder has all the images you need as well. It also has
the complete game, Dragon.sb, in case you get stuck.
1 ' Dragon_Incomplete.sb
2 SetUp() ' Does one-time set up
3
4 NewGame() ' Sets the parameters for a new game
5
6 UpdateUserInterface() ' Shows values on background image
7
8 NextMove:
9 GetChoice() ' Displays options and gets the knight's choice
10
11 ProcessChoice() ' Processes the user's choice
12
13 DragonFire() ' Now it's the dragon's turn
14 Goto NextMove
Listing 10-7: High-level structure of the dragon game
First, you call the SetUp() subroutine (line 2) to draw the background
image, create text shapes (for displaying the distance, number of arrows, and
so on), and load the game’s images (dragon, knight, and arrow). Line 4
calls NewGame() to set the parameters for a new game, including the knight’s
arrows, shield strength, and distance from the dragon. In line 6, you call
UpdateUserInterface() to update the game’s user interface (UI). Then the code
goes into a loop (lines 8–14) to manage the game. Each round, you ask the
knight for his next move (line 9), process his move by calling ProcessChoice()
on line 11, and then give the dragon a turn (line 13). As you’ll see in a
moment, these subroutines will keep track of the game’s status and end the
game when there’s a winner!
Solving Problems with Subroutines 139