blitz
/
blitz3d
-ын хуулбар https://github.com/blitz-research/blitz3d.git


			
				
					
						
						
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<TITLE>Getting Started In Blitz BASIC</TITLE>
</HEAD>
<body bgcolor="#206060" text="#ffff00" link="#00ff00"
vlink="#00ff00" alink="#00ff00">
<style>
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<h2><font color="#FFFF00" face="MS Sans Serif"><strong>Getting
Started with BlitzBasic</strong></font></h2>
<hr>
<menu>
    <li><h4><a href="#first"><font face="MS Sans Serif">My First
        Program</font></a></h4>
    </li>
    <li><h4><a href="#variables"><font face="MS Sans Serif">Variables</font></a></h4>
    </li>
    <li><h4><a href="#firstgame"><font face="MS Sans Serif">My
        First Game</font></a></h4>
    </li>
    <li><h4><a href="#gettinggraphic"><font face="MS Sans Serif">Getting
        Graphic</font></a></h4>
    </li>
    <li><h4><a href="#doublebuffering"><font face="MS Sans Serif">Double
        Buffering</font></a></h4>
    </li>
    <li><h4><a href="#mysecondgame"><font face="MS Sans Serif">My
        Second Game</font></a></h4>
    </li>
</menu>

<hr>

<h4><a name="first"><font color="#A7E3F5" face="MS Sans Serif">My
First Program</font></a></h4>

<p><font face="MS Sans Serif">After sampling some of the fine
example programs included in the BlitzBasic package you are
hopefully itching to try some of your own code.</font></p>

<p><font face="MS Sans Serif">BlitzBasic is intended as both a
friendly introduction to programming computers as well as a
language capable of producing polished video game software.</font></p>

<p><font face="MS Sans Serif">First up, the traditonal hello
world program. A simple one line program that prints the message
&quot;hello world&quot; on the screen. Select the File-New menu
option and enter the following text:</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFE75F" size="2" face="blitz">Print</font><font
        color="#FFFFFF" size="2" face="blitz"> </font><font
        color="#00FF00" size="2" face="blitz">&quot;Hello World!&quot;</font></td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">If you press the F5 key to compile
and run and a message greeting the world appears then </font><font
color="#80FF00" face="MS Sans Serif">congratulations!</font><font
face="MS Sans Serif"> you have just authored your first
BlitzBasic program.</font></p>

<p><font face="MS Sans Serif">The following code illustrates
prompting the user of your program for some input.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFFFFF" size="2" face="blitz">a</font><font
        color="#FFF0C8" size="2" face="blitz">=</font><font
        color="#FFE75F" size="2" face="blitz">Input</font><font
        color="#FFF0C8" size="2" face="blitz">(</font><font
        color="#00FF00" size="2" face="blitz">&quot;enter a
        number sweety:&quot;</font><font color="#FFF0C8" size="2"
        face="blitz">)</font><p><font color="#FFE75F" size="2"
        face="blitz">Print</font><font color="#FFFFFF" size="2"
        face="blitz"> </font><font color="#00FF00" size="2"
        face="blitz">&quot;the value of a is &quot;</font><font
        color="#FFFFFF" size="2" face="blitz"> </font><font
        color="#FFF0C8" size="2" face="blitz">+ </font><font
        color="#FFFFFF" size="2" face="blitz">a</font></p>
        </td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">Note: see how we add text and an
integer variable together to print them both on the same line.</font></p>

<hr>

<h4><a name="variables"><font color="#A7E3F5"
face="MS Sans Serif">Variables</font></a></h4>

<p><font face="MS Sans Serif">Variables in Blitz are used to
store integers, floats and strings.</font></p>

<p><font face="MS Sans Serif">The first time a float or a string
variable is used in your program it must be denoted with # or $
symbols .</font></p>

<p><font face="MS Sans Serif">If the &quot;a=&quot; in the
program is changed to &quot;a$=&quot; Blitz will treat a as a
string variable which can then contain any text the user enters
instead of the integer number it originally converted the user's
reply into.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFFFFF" size="2" face="blitz">a</font><font
        color="#FFF0C8" size="2" face="blitz">$=</font><font
        color="#FFE75F" size="2" face="blitz">Input</font><font
        color="#FFF0C8" size="2" face="blitz">(</font><font
        color="#00FF00" size="2" face="blitz">&quot;enter a
        number sweety:&quot;</font><font color="#FFF0C8" size="2"
        face="blitz">)</font><p><font color="#FFE75F" size="2"
        face="blitz">Print</font><font color="#FFFFFF" size="2"
        face="blitz"> </font><font color="#00FF00" size="2"
        face="blitz">&quot;the value of a is &quot;</font><font
        color="#FFFFFF" size="2" face="blitz"> </font><font
        color="#FFF0C8" size="2" face="blitz">+ </font><font
        color="#FFFFFF" size="2" face="blitz">a</font></p>
        </td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">Suggestion: change the &quot;a$=&quot;
to &quot;a#=&quot; and enter the number 22.95. What's going on?</font></p>

<hr>

<h4><a name="firstgame"><font color="#A7E3F5"
face="MS Sans Serif">My First Game</font></a></h4>

<p><font face="MS Sans Serif">The following program gives the
user 5 turns to guess the random number.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#00FFFF" size="2" face="blitz">;
        guessing game</font><p><font color="#FFFFFF" size="2"
        face="blitz">turnsleft</font><font color="#FFF0C8"
        size="2" face="blitz">=</font><font color="#C8F0FF"
        size="2" face="blitz">5</font></p>
        <p><font color="#FFFFFF" size="2" face="blitz">sheep</font><font
        color="#FFF0C8" size="2" face="blitz">=</font><font
        color="#FFE75F" size="2" face="blitz">Rnd</font><font
        color="#FFF0C8" size="2" face="blitz">(</font><font
        color="#C8F0FF" size="2" face="blitz">20</font><font
        color="#FFF0C8" size="2" face="blitz">)</font></p>
        <p><font color="#FFE75F" size="2" face="blitz">While</font><font
        color="#FFF0C8" size="2" face="blitz"> (</font><font
        color="#FFFFFF" size="2" face="blitz">turnsleft</font><font
        color="#FFF0C8" size="2" face="blitz">&gt;</font><font
        color="#C8F0FF" size="2" face="blitz">0</font><font
        color="#FFF0C8" size="2" face="blitz">)</font></p>
        <blockquote>
            <p><font color="#FFFFFF" size="2" face="blitz">turnsleft</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFFFFF" size="2" face="blitz">turnsleft</font><font
            color="#FFF0C8" size="2" face="blitz">-</font><font
            color="#C8F0FF" size="2" face="blitz">1</font></p>
            <p><font color="#FFFFFF" size="2" face="blitz">guess</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFE75F" size="2" face="blitz">Input</font><font
            color="#FFF0C8" size="2" face="blitz">(</font><font
            color="#00FF00" size="2" face="blitz">&quot;guess how
            many sheep I have in my room:&quot;</font><font
            color="#FFF0C8" size="2" face="blitz">)</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">If</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#FFFFFF" size="2" face="blitz">guess</font><font
            color="#FFF0C8" size="2" face="blitz">&lt;</font><font
            color="#FFFFFF" size="2" face="blitz">sheep</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#FFE75F" size="2" face="blitz">Then</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#FFE75F" size="2" face="blitz">Print</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#00FF00" size="2" face="blitz">&quot;more than
            that!&quot;</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">If</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#FFFFFF" size="2" face="blitz">guess</font><font
            color="#FFF0C8" size="2" face="blitz">&gt;</font><font
            color="#FFFFFF" size="2" face="blitz">sheep</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#FFE75F" size="2" face="blitz">Then</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#FFE75F" size="2" face="blitz">Print</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#00FF00" size="2" face="blitz">&quot;oh, not
            that many!</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">If</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#FFFFFF" size="2" face="blitz">guess</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFFFFF" size="2" face="blitz">sheep</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#FFE75F" size="2" face="blitz">Then</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#FFE75F" size="2" face="blitz">Exit</font></p>
        </blockquote>
        <p><font color="#FFE75F" size="2" face="blitz">Wend</font></p>
        <p><font color="#FFE75F" size="2" face="blitz">If</font><font
        color="#FFF0C8" size="2" face="blitz"> </font><font
        color="#FFFFFF" size="2" face="blitz">turnsleft</font><font
        color="#FFF0C8" size="2" face="blitz">=</font><font
        color="#C8F0FF" size="2" face="blitz">0</font><font
        color="#FFF0C8" size="2" face="blitz"> </font><font
        color="#FFE75F" size="2" face="blitz">Then</font><font
        color="#FFF0C8" size="2" face="blitz"> </font><font
        color="#FFE75F" size="2" face="blitz">Print</font><font
        color="#FFF0C8" size="2" face="blitz"> </font><font
        color="#00FF00" size="2" face="blitz">&quot;game over
        dude&quot; </font><font color="#FFE75F" size="2"
        face="blitz">Else</font><font color="#FFF0C8" size="2"
        face="blitz"> </font><font color="#FFE75F" size="2"
        face="blitz">Print</font><font color="#FFF0C8" size="2"
        face="blitz"> </font><font color="#00FF00" size="2"
        face="blitz">&quot;good guess!&quot;</font></p>
        </td>
    </tr>
</table>
</center></div>

<blockquote>
</blockquote>

<p><font face="MS Sans Serif">There are three variables used in
this program: turnsleft, sheep and guess.</font></p>

<p><font face="MS Sans Serif">To begin with, turnsleft is set to
5 and sheep is set to a random number between 0 and 20. The
program then enters a &quot;while&quot; loop asking the player to
guess a number, and comparing their answer which is placed in the
variable guess with the value in sheep.</font></p>

<p><font face="MS Sans Serif">After playing the game a few times,
you may notice that the number of sheep does not vary much. Try
adding the following line to the top of the program to &quot;seed&quot;
the random number generator using the time of day in milliseconds.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFE75F" size="2" face="blitz">SeedRnd
        MilliSecs</font><font color="#FFF0C8" size="2"
        face="blitz">()</font></td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">Congratulations, you have just
doubled the playability of the game with one line of code!</font></p>

<hr>

<h4><a name="gettinggraphic"><font color="#A7E3F5"
face="MS Sans Serif">Getting Graphic</font></a></h4>

<p><font face="MS Sans Serif">BlitzBasic is not designed for
building text based application such as our initial guessing game.
It is also not designed for building applications featuring
friendly graphics user interfaces filled with windows and sliders.</font></p>

<p><font face="MS Sans Serif">The only thing BlitzBasic has been
designed for is the very serious business of video game
development.</font></p>

<p><font face="MS Sans Serif">The following program initializes a
640x480 video display then plots points at random positions until
the user presses the escape key.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#00FFFF" size="2" face="blitz">; getting
        graphic</font><p><font color="#FFE75F" size="2"
        face="blitz">Graphics</font><font color="#00FFFF"
        size="2" face="blitz"> </font><font color="#C8F0FF"
        size="2" face="blitz">640</font><font color="#FFF0C8"
        size="2" face="blitz">,</font><font color="#C8F0FF"
        size="2" face="blitz">480</font></p>
        <p><font color="#FFE75F" size="2" face="blitz">While</font><font
        color="#00FFFF" size="2" face="blitz"> </font><font
        color="#FFE75F" size="2" face="blitz">Not KeyDown</font><font
        color="#FFF0C8" size="2" face="blitz">(</font><font
        color="#C8F0FF" size="2" face="blitz">1</font><font
        color="#FFF0C8" size="2" face="blitz">)</font></p>
        <blockquote>
            <p><font color="#FFE75F" size="2" face="blitz">Plot</font><font
            color="#00FFFF" size="2" face="blitz"> </font><font
            color="#FFE75F" size="2" face="blitz">Rnd</font><font
            color="#FFF0C8" size="2" face="blitz">(</font><font
            color="#C8F0FF" size="2" face="blitz">640</font><font
            color="#FFF0C8" size="2" face="blitz">),</font><font
            color="#FFE75F" size="2" face="blitz">Rnd</font><font
            color="#FFF0C8" size="2" face="blitz">(</font><font
            color="#C8F0FF" size="2" face="blitz">480</font><font
            color="#FFF0C8" size="2" face="blitz">)</font></p>
        </blockquote>
        <p><font color="#FFE75F" size="2" face="blitz">Wend</font></p>
        </td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">Once again we rely on the random
number generator to provide an interesting result. Try adding the
following color command before the plot statement to vary the
color of the dots.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFE75F" size="2" face="blitz">Color Rnd</font><font
        color="#FFF0C8" size="2" face="blitz">(</font><font
        color="#C8F0FF" size="2" face="blitz">256</font><font
        color="#FFF0C8" size="2" face="blitz">),</font><font
        color="#FFE75F" size="2" face="blitz">Rnd</font><font
        color="#FFF0C8" size="2" face="blitz">(</font><font
        color="#C8F0FF" size="2" face="blitz">256</font><font
        color="#FFF0C8" size="2" face="blitz">),</font><font
        color="#FFE75F" size="2" face="blitz">Rnd</font><font
        color="#FFF0C8" size="2" face="blitz">(</font><font
        color="#C8F0FF" size="2" face="blitz">256</font><font
        color="#FFF0C8" size="2" face="blitz">)</font></td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">Although this may seem like a
simple program, creating a DirectX display such as featured here
using traditional methods can be a complex task. BlitzBasic makes
it so easy!</font></p>

<hr>

<h4><a name="doublebuffering"><font color="#A7E3F5"
face="MS Sans Serif">Double Buffering</font></a></h4>

<p><font face="MS Sans Serif">The following code illustrates the
typical &quot;main loop&quot; of a game. For a video game to
display smoothly animated graphics it must use a technique called
&quot;Double Buffering&quot;.</font></p>

<p><font face="MS Sans Serif">The following program shows one
frame (the FrontBuffer) while drawing to another frame (the
BackBuffer).</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#00FFFF" size="2" face="blitz">; double
        buffering</font><p><font color="#FFE75F" size="2"
        face="blitz">Graphics</font><font color="#FFF0C8"
        size="2" face="blitz"> </font><font color="#C8F0FF"
        size="2" face="blitz">640</font><font color="#FFF0C8"
        size="2" face="blitz">,</font><font color="#C8F0FF"
        size="2" face="blitz">480</font></p>
        <p><font color="#FFE75F" size="2" face="blitz">SetBuffer</font><font
        color="#FFF0C8" size="2" face="blitz"> </font><font
        color="#FFE75F" size="2" face="blitz">BackBuffer</font><font
        color="#FFF0C8" size="2" face="blitz">()</font></p>
        <p><font color="#FFE75F" size="2" face="blitz">While</font><font
        color="#FFF0C8" size="2" face="blitz"> </font><font
        color="#FFE75F" size="2" face="blitz">Not KeyDown</font><font
        color="#FFF0C8" size="2" face="blitz">(</font><font
        color="#C8F0FF" size="2" face="blitz">1</font><font
        color="#FFF0C8" size="2" face="blitz">)</font></p>
        <blockquote>
            <p><font color="#FFE75F" size="2" face="blitz">Flip</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">Cls</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">Line</font><font
            color="#FFF0C8" size="2" face="blitz"> </font><font
            color="#C8F0FF" size="2" face="blitz">320</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">240</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">320</font><font
            color="#FFF0C8" size="2" face="blitz">+</font><font
            color="#C8F0FF" size="2" face="blitz">100</font><font
            color="#FFF0C8" size="2" face="blitz">*</font><font
            color="#FFE75F" size="2" face="blitz">Cos</font><font
            color="#FFF0C8" size="2" face="blitz">(</font><font
            color="#FFFFFF" size="2" face="blitz">a</font><font
            color="#FFF0C8" size="2" face="blitz">),</font><font
            color="#C8F0FF" size="2" face="blitz">240</font><font
            color="#FFF0C8" size="2" face="blitz">+</font><font
            color="#C8F0FF" size="2" face="blitz">100</font><font
            color="#FFF0C8" size="2" face="blitz">*</font><font
            color="#FFE75F" size="2" face="blitz">Sin</font><font
            color="#FFF0C8" size="2" face="blitz">(</font><font
            color="#FFFFFF" size="2" face="blitz">a</font><font
            color="#FFF0C8" size="2" face="blitz">)</font></p>
            <p><font color="#FFFFFF" size="2" face="blitz">a</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFFFFF" size="2" face="blitz">a</font><font
            color="#FFF0C8" size="2" face="blitz">+</font><font
            color="#C8F0FF" size="2" face="blitz">1</font></p>
        </blockquote>
        <p><font color="#FFE75F" size="2" face="blitz">Wend</font></p>
        </td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">In BlitzBasic the Flip command
performs the double buffering by swapping the back and front
buffers. The </font><font color="#FFFF00" face="MS Sans Serif">Cls</font><font
face="MS Sans Serif"> command clears the screen and the </font><font
color="#FFFF00" face="MS Sans Serif">Line</font><font
face="MS Sans Serif"> command draws a line.</font></p>

<p><font face="MS Sans Serif">Note: the flip command also
synchronizes to the video refresh which on standard VGA monitors
is 60 frames per second. </font></p>

<p><font face="MS Sans Serif">The program draws a line from the
center of the screen (320,240) at an angle of a degrees, 100
pixels long.</font></p>

<p><font face="MS Sans Serif">Try changing the program to add 6
to the value of a. If the frame rate of your monitor is 60 frames
per second, and a is incrementing by 6 each frame, in theory it
should increment by 360 every second which is equivalent to a
complete rotation in the world of degrees.</font></p>

<hr>

<h4><a name="mysecondgame"><font color="#A7E3F5"
face="MS Sans Serif">My Second Game</font></a></h4>

<p><font face="MS Sans Serif">The following introduces the basic
skeleton of a simple video game. </font></p>

<p><font face="MS Sans Serif">The status variable contains the
&quot;state&quot; of the game, which is either displaying a title
page or allowing the player to steer round the screen. Extra
states such as player dies with cosmic explosion and gameover
screen would be added to extend the game further.</font></p>

<p><font face="MS Sans Serif">Reading through the program, the
display is initialized in a similar manned to the previous
example using the Graphics and SetBuffer commands. The main loop,
then uses the Flip command to perform the double buffering (allowing
us to draw to one screen while the other is displayed) and then
either prints a message informing the user to press Enter to
start or calls the UpdatePlayer() function.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#00FFFF" size="2" face="blitz">; eat the
        dots</font><p><font color="#FFE75F" size="2" face="blitz">Graphics
        </font><font color="#C8F0FF" size="2" face="blitz">640</font><font
        color="#FFF0C8" size="2" face="blitz">,</font><font
        color="#C8F0FF" size="2" face="blitz">480</font></p>
        <p><font color="#FFE75F" size="2" face="blitz">SetBuffer
        BackBuffer</font><font color="#FFF0C8" size="2"
        face="blitz">()</font></p>
        <p><font color="#FFE75F" size="2" face="blitz">Global</font><font
        color="#FFFFFF" size="2" face="blitz"> status</font><font
        color="#FFF0C8" size="2" face="blitz">=</font><font
        color="#C8F0FF" size="2" face="blitz">0</font><font
        color="#FFF0C8" size="2" face="blitz">,</font><font
        color="#FFFFFF" size="2" face="blitz">x</font><font
        color="#FFF0C8" size="2" face="blitz">#=</font><font
        color="#C8F0FF" size="2" face="blitz">0</font><font
        color="#FFF0C8" size="2" face="blitz">,</font><font
        color="#FFFFFF" size="2" face="blitz">y</font><font
        color="#FFF0C8" size="2" face="blitz">#=</font><font
        color="#C8F0FF" size="2" face="blitz">0</font><font
        color="#FFF0C8" size="2" face="blitz">,</font><font
        color="#FFFFFF" size="2" face="blitz">speed</font><font
        color="#FFF0C8" size="2" face="blitz">#=</font><font
        color="#C8F0FF" size="2" face="blitz">1</font><font
        color="#FFF0C8" size="2" face="blitz">,</font><font
        color="#FFFFFF" size="2" face="blitz">dir</font><font
        color="#FFF0C8" size="2" face="blitz">=</font><font
        color="#C8F0FF" size="2" face="blitz">1</font></p>
        <p><font color="#00FFFF" size="2" face="blitz">; main
        loop</font></p>
        <p><font color="#FFE75F" size="2" face="blitz">While Not</font><font
        color="#FFFFFF" size="2" face="blitz"> </font><font
        color="#FFE75F" size="2" face="blitz">KeyHit</font><font
        color="#FFF0C8" size="2" face="blitz">(</font><font
        color="#C8F0FF" size="2" face="blitz">1</font><font
        color="#FFF0C8" size="2" face="blitz">)</font></p>
        <p><font color="#00FFFF" size="2" face="blitz">; refresh
        screen</font></p>
        <blockquote>
            <p><font color="#FFE75F" size="2" face="blitz">Flip</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">Cls</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">Color </font><font
            color="#C8F0FF" size="2" face="blitz">255</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">255</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">0</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">Rect </font><font
            color="#C8F0FF" size="2" face="blitz">0</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">0</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">640</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">480</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">0</font></p>
            <p><font color="#00FFFF" size="2" face="blitz">;
            select state</font></p>
        </blockquote>
        <blockquote>
            <p><font color="#FFE75F" size="2" face="blitz">Select
            </font><font color="#FFFFFF" size="2" face="blitz">status</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">Case </font><font
            color="#C8F0FF" size="2" face="blitz">0</font></p>
            <blockquote>
                <p><font color="#FFE75F" size="2" face="blitz">Locate
                </font><font color="#C8F0FF" size="2"
                face="blitz">100</font><font color="#FFF0C8"
                size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">100</font></p>
                <p><font color="#FFE75F" size="2" face="blitz">Print
                </font><font color="#00FF00" size="2"
                face="blitz">&quot;Press Enter To Start&quot;</font></p>
                <p><font color="#FFE75F" size="2" face="blitz">If
                KeyHit</font><font color="#FFF0C8" size="2"
                face="blitz">(28)</font><font color="#C8F0FF"
                size="2" face="blitz"> </font><font
                color="#FFFFFF" size="2" face="blitz">InitGame</font><font
                color="#FFF0C8" size="2" face="blitz">() </font></p>
            </blockquote>
            <p><font color="#FFE75F" size="2" face="blitz">Case </font><font
            color="#C8F0FF" size="2" face="blitz">1</font></p>
            <blockquote>
                <p><font color="#FFFFFF" size="2" face="blitz">UpdatePlayer</font><font
                color="#FFF0C8" size="2" face="blitz">()</font></p>
            </blockquote>
            <p><font color="#FFE75F" size="2" face="blitz">End
            Select</font></p>
        </blockquote>
        <p><font color="#FFE75F" size="2" face="blitz">Wend</font></p>
        </td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">What UpdatePlayer() function you
ask? And if the user presses Enter what's this InitGame()
function?</font></p>

<p><font face="MS Sans Serif">Unlike traditional BASIC languages
where we would implement these functions as subroutines and call
them with the Gosub command BlitzBasic features user defined
functions. </font></p>

<p><font face="MS Sans Serif">Add the following two functions at
the bottom of the above program to allow the program to run.</font></p>

<p><font face="MS Sans Serif">The first function initializes the
variables we will need inorder to steer the players rectangle
around the screen. Note how these variables have been declared at
the top of the program as Global which allows us to access them
from inside functions such as InitGame().</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFE75F" size="2" face="blitz">Function</font><font
        color="#FFFFFF" size="2" face="blitz"> InitGame</font><font
        color="#FFF0C8" size="2" face="blitz">()</font><blockquote>
            <p><font color="#FFFFFF" size="2" face="blitz">x</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#C8F0FF" size="2" face="blitz">320</font></p>
            <p><font color="#FFFFFF" size="2" face="blitz">y</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#C8F0FF" size="2" face="blitz">240</font></p>
            <p><font color="#FFFFFF" size="2" face="blitz">speed</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#C8F0FF" size="2" face="blitz">1</font></p>
            <p><font color="#FFFFFF" size="2" face="blitz">dir</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#C8F0FF" size="2" face="blitz">1</font></p>
            <p><font color="#FFFFFF" size="2" face="blitz">status</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#C8F0FF" size="2" face="blitz">1</font></p>
        </blockquote>
        <p><font color="#FFE75F" size="2" face="blitz">End
        Function</font><font color="#FFF0C8" size="2"
        face="blitz"> </font></p>
        </td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">This second function changes the
players direction depending on the arrow key they are pressing or
the direction of the joystick. The code then moves the players
position (x,y) depending on the dir variable which corresponds to
up, right, down and left respectively.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFE75F" size="2" face="blitz">Function </font><font
        color="#FFFFFF" size="2" face="blitz">UpdatePlayer</font><font
        color="#FFF0C8" size="2" face="blitz">()</font><blockquote>
            <p><font color="#00FFFF" size="2" face="blitz">;
            steer player </font></p>
            <p><font color="#FFE75F" size="2" face="blitz">If
            KeyDown</font><font color="#FFF0C8" size="2"
            face="blitz">(</font><font color="#C8F0FF" size="2"
            face="blitz">200</font><font color="#FFF0C8" size="2"
            face="blitz">) </font><font color="#FFE75F" size="2"
            face="blitz">Or JoyY</font><font color="#FFF0C8"
            size="2" face="blitz">()&lt;-</font><font
            color="#C8F0FF" size="2" face="blitz">0</font><font
            color="#FFF0C8" size="2" face="blitz">.</font><font
            color="#C8F0FF" size="2" face="blitz">5 </font><font
            color="#FFFFFF" size="2" face="blitz">dir</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#C8F0FF" size="2" face="blitz">0</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">If
            KeyDown</font><font color="#FFF0C8" size="2"
            face="blitz">(</font><font color="#C8F0FF" size="2"
            face="blitz">205</font><font color="#FFF0C8" size="2"
            face="blitz">) </font><font color="#FFE75F" size="2"
            face="blitz">Or JoyX</font><font color="#FFF0C8"
            size="2" face="blitz">()&gt;</font><font
            color="#C8F0FF" size="2" face="blitz">0</font><font
            color="#FFF0C8" size="2" face="blitz">.</font><font
            color="#C8F0FF" size="2" face="blitz">5 </font><font
            color="#FFFFFF" size="2" face="blitz">dir</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#C8F0FF" size="2" face="blitz">1</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">If
            KeyDown</font><font color="#FFF0C8" size="2"
            face="blitz">(</font><font color="#C8F0FF" size="2"
            face="blitz">208</font><font color="#FFF0C8" size="2"
            face="blitz">) </font><font color="#FFE75F" size="2"
            face="blitz">Or JoyY</font><font color="#FFF0C8"
            size="2" face="blitz">()&gt;</font><font
            color="#C8F0FF" size="2" face="blitz">0</font><font
            color="#FFF0C8" size="2" face="blitz">.</font><font
            color="#C8F0FF" size="2" face="blitz">5 </font><font
            color="#FFFFFF" size="2" face="blitz">dir</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#C8F0FF" size="2" face="blitz">2</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">If
            KeyDown</font><font color="#FFF0C8" size="2"
            face="blitz">(</font><font color="#C8F0FF" size="2"
            face="blitz">203</font><font color="#FFF0C8" size="2"
            face="blitz">) </font><font color="#FFE75F" size="2"
            face="blitz">Or JoyX</font><font color="#FFF0C8"
            size="2" face="blitz">()&lt;-</font><font
            color="#C8F0FF" size="2" face="blitz">0</font><font
            color="#FFF0C8" size="2" face="blitz">.</font><font
            color="#C8F0FF" size="2" face="blitz">5 </font><font
            color="#FFFFFF" size="2" face="blitz">dir</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#C8F0FF" size="2" face="blitz">3</font></p>
            <p><font color="#00FFFF" size="2" face="blitz">; move
            player</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">Select
            </font><font color="#FFFFFF" size="2" face="blitz">dir</font></p>
            <blockquote>
                <p><font color="#FFE75F" size="2" face="blitz">Case
                </font><font color="#C8F0FF" size="2"
                face="blitz">0 </font><font color="#FFFFFF"
                size="2" face="blitz">y</font><font
                color="#FFF0C8" size="2" face="blitz">=</font><font
                color="#FFFFFF" size="2" face="blitz">y</font><font
                color="#FFF0C8" size="2" face="blitz">-</font><font
                color="#FFFFFF" size="2" face="blitz">speed</font></p>
                <p><font color="#FFE75F" size="2" face="blitz">Case
                </font><font color="#C8F0FF" size="2"
                face="blitz">1 </font><font color="#FFFFFF"
                size="2" face="blitz">x</font><font
                color="#FFF0C8" size="2" face="blitz">=</font><font
                color="#FFFFFF" size="2" face="blitz">x</font><font
                color="#FFF0C8" size="2" face="blitz">+</font><font
                color="#FFFFFF" size="2" face="blitz">speed</font></p>
                <p><font color="#FFE75F" size="2" face="blitz">Case
                </font><font color="#C8F0FF" size="2"
                face="blitz">2 </font><font color="#FFFFFF"
                size="2" face="blitz">y</font><font
                color="#FFF0C8" size="2" face="blitz">=</font><font
                color="#FFFFFF" size="2" face="blitz">y</font><font
                color="#FFF0C8" size="2" face="blitz">+</font><font
                color="#FFFFFF" size="2" face="blitz">speed</font></p>
                <p><font color="#FFE75F" size="2" face="blitz">Case
                </font><font color="#C8F0FF" size="2"
                face="blitz">3 </font><font color="#FFFFFF"
                size="2" face="blitz">x</font><font
                color="#FFF0C8" size="2" face="blitz">=</font><font
                color="#FFFFFF" size="2" face="blitz">x</font><font
                color="#FFF0C8" size="2" face="blitz">-</font><font
                color="#FFFFFF" size="2" face="blitz">speed</font></p>
            </blockquote>
            <p><font color="#FFE75F" size="2" face="blitz">End
            Select</font></p>
            <p><font color="#00FFFF" size="2" face="blitz">; draw
            player </font></p>
            <p><font color="#FFE75F" size="2" face="blitz">Color </font><font
            color="#C8F0FF" size="2" face="blitz">255</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">255</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">255</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">Rect </font><font
            color="#FFFFFF" size="2" face="blitz">x</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#FFFFFF" size="2" face="blitz">y</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">10</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">10</font></p>
        </blockquote>
        <p><font color="#FFE75F" size="2" face="blitz">End
        Function</font></p>
        </td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">After adding the InitGame() and
UpdatePlayer() code the game should run.</font></p>

<p><font face="MS Sans Serif">Next it's time to add some deadly
rocks and some yummy food. </font></p>

<p><font face="MS Sans Serif">In order to do this we create some
new Types that will hold all the information we need for each
rock and food. To begin with these Types will simply hold the x
and y position of each rock and food element we create for our
game.</font></p>

<p><font face="MS Sans Serif">Place the following Type
declarations at the top of the program.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFE75F" size="2" face="blitz">Type </font><font
        color="#FFFFFF" size="2" face="blitz">food</font><blockquote>
            <p><font color="#FFE75F" size="2" face="blitz">Field </font><font
            color="#FFFFFF" size="2" face="blitz">x</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#FFFFFF" size="2" face="blitz">y</font></p>
        </blockquote>
        <p><font color="#FFE75F" size="2" face="blitz">End Type</font></p>
        <p><font color="#FFE75F" size="2" face="blitz">Type </font><font
        color="#FFFFFF" size="2" face="blitz">rock</font></p>
        <blockquote>
            <p><font color="#FFE75F" size="2" face="blitz">Field </font><font
            color="#FFFFFF" size="2" face="blitz">x</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#FFFFFF" size="2" face="blitz">y</font></p>
        </blockquote>
        <p><font color="#FFE75F" size="2" face="blitz">End Type</font></p>
        </td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">The following code then needs to be
added to the InitGame() function, insert it after the line that
reads status=1.</font></p>

<p><font face="MS Sans Serif">This code creates 20 rocks that
will kill the player and 20 food that will speed the player up.
The New command creates a new object and also adds it to a list.
We set the position of each rock and food by setting the x and y
fields of each new object created using the backslash \ character
to denote which field.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFE75F" size="2" face="blitz">For </font><font
        color="#FFFFFF" size="2" face="blitz">i</font><font
        color="#FFF0C8" size="2" face="blitz">=</font><font
        color="#C8F0FF" size="2" face="blitz">0 </font><font
        color="#FFE75F" size="2" face="blitz">To </font><font
        color="#C8F0FF" size="2" face="blitz">20 </font><blockquote>
            <p><font color="#FFFFFF" size="2" face="blitz">r</font><font
            color="#FFF0C8" size="2" face="blitz">.</font><font
            color="#FFFFFF" size="2" face="blitz">rock</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFE75F" size="2" face="blitz">New </font><font
            color="#FFFFFF" size="2" face="blitz">rock</font></p>
            <p><font color="#FFFFFF" size="2" face="blitz">r</font><font
            color="#FFF0C8" size="2" face="blitz">\</font><font
            color="#FFFFFF" size="2" face="blitz">x</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFE75F" size="2" face="blitz">Rnd</font><font
            color="#FFF0C8" size="2" face="blitz">(</font><font
            color="#C8F0FF" size="2" face="blitz">640</font><font
            color="#FFF0C8" size="2" face="blitz">)</font></p>
            <p><font color="#FFFFFF" size="2" face="blitz">r</font><font
            color="#FFF0C8" size="2" face="blitz">\</font><font
            color="#FFFFFF" size="2" face="blitz">y</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFE75F" size="2" face="blitz">Rnd</font><font
            color="#FFF0C8" size="2" face="blitz">(</font><font
            color="#C8F0FF" size="2" face="blitz">480</font><font
            color="#FFF0C8" size="2" face="blitz">)</font></p>
        </blockquote>
        <p><font color="#FFE75F" size="2" face="blitz">Next</font></p>
        <p><font color="#FFE75F" size="2" face="blitz">For </font><font
        color="#FFFFFF" size="2" face="blitz">i</font><font
        color="#FFF0C8" size="2" face="blitz">=</font><font
        color="#C8F0FF" size="2" face="blitz">0 </font><font
        color="#FFE75F" size="2" face="blitz">To </font><font
        color="#C8F0FF" size="2" face="blitz">20 </font></p>
        <blockquote>
            <p><font color="#FFFFFF" size="2" face="blitz">f</font><font
            color="#FFF0C8" size="2" face="blitz">.</font><font
            color="#FFFFFF" size="2" face="blitz">food</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFE75F" size="2" face="blitz">New </font><font
            color="#FFFFFF" size="2" face="blitz">food</font></p>
            <p><font color="#FFFFFF" size="2" face="blitz">f</font><font
            color="#FFF0C8" size="2" face="blitz">\</font><font
            color="#FFFFFF" size="2" face="blitz">x</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFE75F" size="2" face="blitz">Rnd</font><font
            color="#FFF0C8" size="2" face="blitz">(</font><font
            color="#C8F0FF" size="2" face="blitz">640</font><font
            color="#FFF0C8" size="2" face="blitz">)</font></p>
            <p><font color="#FFFFFF" size="2" face="blitz">f</font><font
            color="#FFF0C8" size="2" face="blitz">\</font><font
            color="#FFFFFF" size="2" face="blitz">y</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFE75F" size="2" face="blitz">Rnd</font><font
            color="#FFF0C8" size="2" face="blitz">(</font><font
            color="#C8F0FF" size="2" face="blitz">480</font><font
            color="#FFF0C8" size="2" face="blitz">)</font></p>
        </blockquote>
        <p><font color="#FFE75F" size="2" face="blitz">Next</font></p>
        </td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">We now need a function that draws
all the food and rocks each frame and checks if the player has
collided with any.</font></p>

<p><font face="MS Sans Serif">Note how we can loop through each
food and rock element that exist using the For..Each command pair.
This is another great feature of BlitzBasic that keeps programs
simple and easy to read.</font></p>

<p><font face="MS Sans Serif">We use the RectsOverlap command to
check of the players position (x,y) collides with each food or
rock element (f \ x , f \ y) or (r \ x , r \ y). If the player
collides with some food we delete that piece of food and increase
the player's speed. If the player collides with a rock we end the
game by resetting the status variable.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFE75F" size="2" face="blitz">Function </font><font
        color="#FFFFFF" size="2" face="blitz">UpdateRocksandFood</font><font
        color="#FFF0C8" size="2" face="blitz">()</font><blockquote>
            <p><font color="#00FFFF" size="2" face="blitz">; draw
            food and check if eaten</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">Color </font><font
            color="#C8F0FF" size="2" face="blitz">0</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">255</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">0</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">For </font><font
            color="#FFFFFF" size="2" face="blitz">f</font><font
            color="#FFF0C8" size="2" face="blitz">.</font><font
            color="#FFFFFF" size="2" face="blitz">food</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFE75F" size="2" face="blitz">Each </font><font
            color="#FFFFFF" size="2" face="blitz">food </font></p>
            <blockquote>
                <p><font color="#FFE75F" size="2" face="blitz">Rect
                </font><font color="#FFFFFF" size="2"
                face="blitz">f</font><font color="#FFF0C8"
                size="2" face="blitz">\</font><font
                color="#FFFFFF" size="2" face="blitz">x</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#FFFFFF" size="2" face="blitz">f</font><font
                color="#FFF0C8" size="2" face="blitz">\</font><font
                color="#FFFFFF" size="2" face="blitz">y</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font></p>
                <p><font color="#FFE75F" size="2" face="blitz">If
                RectsOverlap</font><font color="#FFF0C8" size="2"
                face="blitz">(</font><font color="#FFFFFF"
                size="2" face="blitz">x</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#FFFFFF" size="2" face="blitz">y</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#FFFFFF" size="2" face="blitz">f</font><font
                color="#FFF0C8" size="2" face="blitz">\</font><font
                color="#FFFFFF" size="2" face="blitz">x</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#FFFFFF" size="2" face="blitz">f</font><font
                color="#FFF0C8" size="2" face="blitz">\</font><font
                color="#FFFFFF" size="2" face="blitz">y</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font><font
                color="#FFF0C8" size="2" face="blitz">)</font></p>
                <blockquote>
                    <p><font color="#FFFFFF" size="2"
                    face="blitz">speed</font><font
                    color="#FFF0C8" size="2" face="blitz">=</font><font
                    color="#FFFFFF" size="2" face="blitz">speed</font><font
                    color="#FFF0C8" size="2" face="blitz">+</font><font
                    color="#C8F0FF" size="2" face="blitz">0</font><font
                    color="#FFF0C8" size="2" face="blitz">.</font><font
                    color="#C8F0FF" size="2" face="blitz">2</font></p>
                    <p><font color="#FFE75F" size="2"
                    face="blitz">Delete </font><font
                    color="#FFFFFF" size="2" face="blitz">f</font></p>
                </blockquote>
                <p><font color="#FFE75F" size="2" face="blitz">EndIf
                </font></p>
            </blockquote>
            <p><font color="#FFE75F" size="2" face="blitz">Next</font></p>
            <p><font color="#00FFFF" size="2" face="blitz">; draw
            rocks and check for roadkill</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">Color </font><font
            color="#C8F0FF" size="2" face="blitz">255</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">0</font><font
            color="#FFF0C8" size="2" face="blitz">,</font><font
            color="#C8F0FF" size="2" face="blitz">255</font></p>
            <p><font color="#FFE75F" size="2" face="blitz">For </font><font
            color="#FFFFFF" size="2" face="blitz">r</font><font
            color="#FFF0C8" size="2" face="blitz">.</font><font
            color="#FFFFFF" size="2" face="blitz">rock</font><font
            color="#FFF0C8" size="2" face="blitz">=</font><font
            color="#FFE75F" size="2" face="blitz">Each </font><font
            color="#FFFFFF" size="2" face="blitz">rock </font></p>
            <blockquote>
                <p><font color="#FFE75F" size="2" face="blitz">Rect
                </font><font color="#FFFFFF" size="2"
                face="blitz">r</font><font color="#FFF0C8"
                size="2" face="blitz">\</font><font
                color="#FFFFFF" size="2" face="blitz">x</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#FFFFFF" size="2" face="blitz">r</font><font
                color="#FFF0C8" size="2" face="blitz">\</font><font
                color="#FFFFFF" size="2" face="blitz">y</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font></p>
                <p><font color="#FFE75F" size="2" face="blitz">If
                RectsOverlap</font><font color="#FFF0C8" size="2"
                face="blitz">(</font><font color="#FFFFFF"
                size="2" face="blitz">x</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#FFFFFF" size="2" face="blitz">y</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#FFFFFF" size="2" face="blitz">r</font><font
                color="#FFF0C8" size="2" face="blitz">\</font><font
                color="#FFFFFF" size="2" face="blitz">x</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#FFFFFF" size="2" face="blitz">r</font><font
                color="#FFF0C8" size="2" face="blitz">\</font><font
                color="#FFFFFF" size="2" face="blitz">y</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font><font
                color="#FFF0C8" size="2" face="blitz">,</font><font
                color="#C8F0FF" size="2" face="blitz">10</font><font
                color="#FFF0C8" size="2" face="blitz">)</font></p>
                <blockquote>
                    <p><font color="#FFFFFF" size="2"
                    face="blitz">status</font><font
                    color="#FFF0C8" size="2" face="blitz">=</font><font
                    color="#C8F0FF" size="2" face="blitz">0</font></p>
                </blockquote>
            </blockquote>
            <blockquote>
                <p><font color="#FFE75F" size="2" face="blitz">EndIf</font></p>
            </blockquote>
            <p><font color="#FFE75F" size="2" face="blitz">Next</font></p>
        </blockquote>
        <p><font color="#FFE75F" size="2" face="blitz">End
        Function</font></p>
        </td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">Oops, one last thing, don't forget
to call the UpdateRocksandFood() function from the main loop,
just after the UpdatePlayer() call should do nicely.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFFFFF" size="2" face="blitz">UpdateRocksandFood</font><font
        color="#FFF0C8" size="2" face="blitz">()</font></td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">OK, after playing the game, a few
things should become evident.</font></p>

<p><font face="MS Sans Serif">First, the player should die if
they hit the outer wall. We could do this by checking if their
position does not collide with the main screen rectangle (0,0,640,480).
Try adding the following code to the UpdatePlayer function.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFE75F" size="2" face="blitz">If Not
        RectsOverlap</font><font color="#FFF0C8" size="2"
        face="blitz">(</font><font color="#FFFFFF" size="2"
        face="blitz">x</font><font color="#FFF0C8" size="2"
        face="blitz">,</font><font color="#FFFFFF" size="2"
        face="blitz">y</font><font color="#FFF0C8" size="2"
        face="blitz">,</font><font color="#C8F0FF" size="2"
        face="blitz">10</font><font color="#FFF0C8" size="2"
        face="blitz">,</font><font color="#C8F0FF" size="2"
        face="blitz">10</font><font color="#FFF0C8" size="2"
        face="blitz">,</font><font color="#C8F0FF" size="2"
        face="blitz">0</font><font color="#FFF0C8" size="2"
        face="blitz">,</font><font color="#C8F0FF" size="2"
        face="blitz">0</font><font color="#FFF0C8" size="2"
        face="blitz">,</font><font color="#C8F0FF" size="2"
        face="blitz">630</font><font color="#FFF0C8" size="2"
        face="blitz">,</font><font color="#C8F0FF" size="2"
        face="blitz">470</font><font color="#FFF0C8" size="2"
        face="blitz">) </font><font color="#FFFFFF" size="2"
        face="blitz">status</font><font color="#FFF0C8" size="2"
        face="blitz">=</font><font color="#C8F0FF" size="2"
        face="blitz">0</font></td>
    </tr>
</table>
</center></div>

<p><font face="MS Sans Serif">Secondly, each time the game starts
more rocks and food appear. This is because we never delete the
food and rocks remaining from the last game. Insert the following
code <strong>before</strong> the code that creates the new food
and rocks in the InitGame() function.</font></p>
<div align="center"><center>

<table border="2" cellpadding="8" width="600" bgcolor="#006060">
    <tr>
        <td><font color="#FFE75F" size="2" face="blitz">For </font><font
        color="#FFFFFF" size="2" face="blitz">f</font><font
        color="#FFF0C8" size="2" face="blitz">.</font><font
        color="#FFFFFF" size="2" face="blitz">food</font><font
        color="#FFF0C8" size="2" face="blitz">=</font><font
        color="#FFE75F" size="2" face="blitz">Each </font><font
        color="#FFFFFF" size="2" face="blitz">food </font><font
        color="#FFE75F" size="2" face="blitz">Delete </font><font
        color="#FFFFFF" size="2" face="blitz">f </font><font
        color="#FFE75F" size="2" face="blitz">Next</font><p><font
        color="#FFE75F" size="2" face="blitz">For </font><font
        color="#FFFFFF" size="2" face="blitz">r</font><font
        color="#FFF0C8" size="2" face="blitz">.</font><font
        color="#FFFFFF" size="2" face="blitz">rock</font><font
        color="#FFF0C8" size="2" face="blitz">=</font><font
        color="#FFE75F" size="2" face="blitz">Each </font><font
        color="#FFFFFF" size="2" face="blitz">rock </font><font
        color="#FFE75F" size="2" face="blitz">Delete </font><font
        color="#FFFFFF" size="2" face="blitz">r </font><font
        color="#FFE75F" size="2" face="blitz">Next</font></p>
        </td>
    </tr>
</table>
</center></div>
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