I've highlighted the code in question in red. Can somebody tell me how the red code makes Pac man and the Ghosts move?
//
// PacMan
// Another 1 day game (created in 5 hours).
//
// (C)2000
// Brian Postma
// [email]b.postma@hetnet.nl[/email]
// [url]http://www.homepages.hetnet.nl/~brianpostma[/url]
//
import java.awt.*;
import java.applet.Applet;
public class PacMan extends Applet implements Runnable
{
Dimension d;
Font largefont = new Font("Helvetica", Font.BOLD, 24);
Font smallfont = new Font("Helvetica", Font.BOLD, 14);
FontMetrics fmsmall, fmlarge;
Graphics goff;
Image ii;
Thread thethread;
MediaTracker thetracker = null;
Color dotcolor=new Color(192,192,0);
int bigdotcolor=192;
int dbigdotcolor=-2;
Color mazecolor;
boolean ingame=false;
boolean showtitle=true;
boolean scared=false;
boolean dying=false;
final int screendelay=120;
final int blocksize=24;
final int nrofblocks=15;
final int scrsize=nrofblocks*blocksize;
final int animdelay=8;
final int pacanimdelay=2;
final int ghostanimcount=2;
final int pacmananimcount=4;
final int maxghosts=12;
final int pacmanspeed=6;
int animcount=animdelay;
int pacanimcount=pacanimdelay;
int pacanimdir=1;
int count=screendelay;
int ghostanimpos=0;
int pacmananimpos=0;
int nrofghosts=6;
int pacsleft,score;
int deathcounter;
int[] dx,dy;
int[] ghostx, ghosty, ghostdx, ghostdy, ghostspeed;
Image ghost1,ghost2,ghostscared1,ghostscared2;
Image pacman1, pacman2up, pacman2left, pacman2right, pacman2down;
Image pacman3up, pacman3down, pacman3left, pacman3right;
Image pacman4up, pacman4down, pacman4left, pacman4right;
int pacmanx, pacmany, pacmandx, pacmandy;
int reqdx, reqdy, viewdx, viewdy;
int scaredcount, scaredtime;
final int maxscaredtime=120;
final int minscaredtime=20;
final short level1data[] = {
19,26,26,22, 9,12,19,26,22, 9,12,19,26,26,22,
37,11,14,17,26,26,20,15,17,26,26,20,11,14,37,
17,26,26,20,11, 6,17,26,20, 3,14,17,26,26,20,
21, 3, 6,25,22, 5,21, 7,21, 5,19,28, 3, 6,21,
21, 9, 8,14,21,13,21, 5,21,13,21,11, 8,12,21,
25,18,26,18,24,18,28, 5,25,18,24,18,26,18,28,
6,21, 7,21, 7,21,11, 8,14,21, 7,21, 7,21,03,
4,21, 5,21, 5,21,11,10,14,21, 5,21, 5,21, 1,
12,21,13,21,13,21,11,10,14,21,13,21,13,21, 9,
19,24,26,24,26,16,26,18,26,16,26,24,26,24,22,
21, 3, 2, 2, 6,21,15,21,15,21, 3, 2, 2,06,21,
21, 9, 8, 8, 4,17,26, 8,26,20, 1, 8, 8,12,21,
17,26,26,22,13,21,11, 2,14,21,13,19,26,26,20,
37,11,14,17,26,24,22,13,19,24,26,20,11,14,37,
25,26,26,28, 3, 6,25,26,28, 3, 6,25,26,26,28 };
final int validspeeds[] = { 1,2,3,4,6,8 };
final int maxspeed=6;
int currentspeed=3;
short[] screendata;
public String getAppletInfo()
{
return("PacMan - by Brian Postma");
}
public void init()
{
short i;
GetImages();
screendata=new short[nrofblocks*nrofblocks];
Graphics g;
d = size();
setBackground(Color.black);
g=getGraphics();
g.setFont(smallfont);
fmsmall = g.getFontMetrics();
g.setFont(largefont);
fmlarge = g.getFontMetrics();
ghostx=new int[maxghosts];
ghostdx=new int[maxghosts];
ghosty=new int[maxghosts];
ghostdy=new int[maxghosts];
ghostspeed=new int[maxghosts];
dx=new int[4];
dy=new int[4];
GameInit();
}
public void GameInit()
{
pacsleft=3;
score=0;
scaredtime=maxscaredtime;
LevelInit();
nrofghosts=6;
currentspeed=3;
scaredtime=maxscaredtime;
}
public void LevelInit()
{
int i;
for (i=0; i<nrofblocks*nrofblocks; i++)
screendata[i]=level1data[i];
LevelContinue();
}
public void LevelContinue()
{
short i;
int dx=1;
int random;
for (i=0; i<nrofghosts; i++)
{
ghosty[i]=7*blocksize;
ghostx[i]=7*blocksize;
ghostdy[i]=0;
ghostdx[i]=dx;
dx=-dx;
random=(int)(Math.random()*(currentspeed+1));
if (random>currentspeed)
random=currentspeed;
ghostspeed[i]=validspeeds[random];
}
screendata[7*nrofblocks+6]=10;
screendata[7*nrofblocks+8]=10;
pacmanx=7*blocksize;
pacmany=11*blocksize;
pacmandx=0;
pacmandy=0;
reqdx=0;
reqdy=0;
viewdx=-1;
viewdy=0;
dying=false;
scared=false;
}
public void GetImages()
{
thetracker=new MediaTracker(this);
ghost1=getImage(getDocumentBase(),"pacpix/Ghost1.gif");
thetracker.addImage(ghost1,0);
ghost2=getImage(getDocumentBase(),"pacpix/Ghost2.gif");
thetracker.addImage(ghost2,0);
ghostscared1=getImage(getDocumentBase(),"pacpix/GhostScared1.gif");
thetracker.addImage(ghostscared1,0);
ghostscared2=getImage(getDocumentBase(),"pacpix/GhostScared2.gif");
thetracker.addImage(ghostscared2,0);
pacman1=getImage(getDocumentBase(),"pacpix/PacMan1.gif");
thetracker.addImage(pacman1,0);
pacman2up=getImage(getDocumentBase(),"pacpix/PacMan2up.gif");
thetracker.addImage(pacman2up,0);
pacman3up=getImage(getDocumentBase(),"pacpix/PacMan3up.gif");
thetracker.addImage(pacman3up,0);
pacman4up=getImage(getDocumentBase(),"pacpix/PacMan4up.gif");
thetracker.addImage(pacman4up,0);
pacman2down=getImage(getDocumentBase(),"pacpix/PacMan2down.gif");
thetracker.addImage(pacman2down,0);
pacman3down=getImage(getDocumentBase(),"pacpix/PacMan3down.gif");
thetracker.addImage(pacman3down,0);
pacman4down=getImage(getDocumentBase(),"pacpix/PacMan4down.gif");
thetracker.addImage(pacman4down,0);
pacman2left=getImage(getDocumentBase(),"pacpix/PacMan2left.gif");
thetracker.addImage(pacman2left,0);
pacman3left=getImage(getDocumentBase(),"pacpix/PacMan3left.gif");
thetracker.addImage(pacman3left,0);
pacman4left=getImage(getDocumentBase(),"pacpix/PacMan4left.gif");
thetracker.addImage(pacman4left,0);
pacman2right=getImage(getDocumentBase(),"pacpix/PacMan2right.gif");
thetracker.addImage(pacman2right,0);
pacman3right=getImage(getDocumentBase(),"pacpix/PacMan3right.gif");
thetracker.addImage(pacman3right,0);
pacman4right=getImage(getDocumentBase(),"pacpix/PacMan4right.gif");
thetracker.addImage(pacman4right,0);
try
{
thetracker.waitForAll();
}
catch (InterruptedException e)
{
return;
}
}
public boolean keyDown(Event e, int key)
{
if (ingame)
{
if (key == Event.LEFT)
{
reqdx=-1;
reqdy=0;
}
else if (key == Event.RIGHT)
{
reqdx=1;
reqdy=0;
}
else if (key == Event.UP)
{
reqdx=0;
reqdy=-1;
}
else if (key == Event.DOWN)
{
reqdx=0;
reqdy=1;
}
else if (key == Event.ESCAPE)
{
ingame=false;
}
}
else
{
if (key == 's' || key == 'S')
{
ingame=true;
GameInit();
}
}
return true;
}
public boolean keyUp(Event e, int key)
{
if (key == Event.LEFT || key == Event.RIGHT || key == Event.UP || key == Event.DOWN)
{
reqdx=0;
reqdy=0;
}
return true;
}
public void paint(Graphics g)
{
String s;
Graphics gg;
if (goff==null && d.width>0 && d.height>0)
{
ii = createImage(d.width, d.height);
goff = ii.getGraphics();
}
if (goff==null || ii==null)
return;
goff.setColor(Color.black);
goff.fillRect(0, 0, d.width, d.height);
DrawMaze();
DrawScore();
DoAnim();
if (ingame)
PlayGame();
else
PlayDemo();
g.drawImage(ii, 0, 0, this);
}
public void DoAnim()
{
animcount--;
if (animcount<=0)
{
animcount=animdelay;
ghostanimpos++;
if (ghostanimpos>=ghostanimcount)
ghostanimpos=0;
}
pacanimcount--;
if (pacanimcount<=0)
{
pacanimcount=pacanimdelay;
pacmananimpos=pacmananimpos+pacanimdir;
if (pacmananimpos==(pacmananimcount-1) || pacmananimpos==0)
pacanimdir=-pacanimdir;
}
}
public void PlayGame()
{
if (dying)
{
Death();
}
else
{
CheckScared();
MovePacMan();
DrawPacMan();
MoveGhosts();
CheckMaze();
}
}
public void PlayDemo()
{
CheckScared();
MoveGhosts();
ShowIntroScreen();
}
public void Death()
{
int k;
deathcounter--;
k=(deathcounter&15)/4;
switch(k)
{
case 0:
goff.drawImage(pacman4up,pacmanx+1,pacmany+1,this);
break;
case 1:
goff.drawImage(pacman4right,pacmanx+1,pacmany+1,this);
break;
case 2:
goff.drawImage(pacman4down,pacmanx+1,pacmany+1,this);
break;
default:
goff.drawImage(pacman4left,pacmanx+1,pacmany+1,this);
}
if (deathcounter==0)
{
pacsleft--;
if (pacsleft==0)
ingame=false;
LevelContinue();
}
}
public void MoveGhosts()
{
short i;
int pos;
int count;
for (i=0; i<nrofghosts; i++)
{
if (ghostx[i]%blocksize==0 && ghosty[i]%blocksize==0)
{
pos=ghostx[i]/blocksize+nrofblocks*(int)(ghosty[i]/blocksize);
count=0;
if ((screendata[pos]&1)==0 && ghostdx[i]!=1)
{
dx[count]=-1;
dy[count]=0;
count++;
}
if ((screendata[pos]&2)==0 && ghostdy[i]!=1)
{
dx[count]=0;
dy[count]=-1;
count++;
}
if ((screendata[pos]&4)==0 && ghostdx[i]!=-1)
{
dx[count]=1;
dy[count]=0;
count++;
}
if ((screendata[pos]&8)==0 && ghostdy[i]!=-1)
{
dx[count]=0;
dy[count]=1;
count++;
}
if (count==0)
{
if ((screendata[pos]&15)==15)
{
ghostdx[i]=0;
ghostdy[i]=0;
}
else
{
ghostdx[i]=-ghostdx[i];
ghostdy[i]=-ghostdy[i];
}
}
else
{
count=(int)(Math.random()*count);
if (count>3) count=3;
ghostdx[i]=dx[count];
ghostdy[i]=dy[count];
}
}
ghostx[i]=ghostx[i]+(ghostdx[i]*ghostspeed[i]);
ghosty[i]=ghosty[i]+(ghostdy[i]*ghostspeed[i]);
DrawGhost(ghostx[i]+1,ghosty[i]+1);
if (pacmanx>(ghostx[i]-12) && pacmanx<(ghostx[i]+12) &&
pacmany>(ghosty[i]-12) && pacmany<(ghosty[i]+12) && ingame)
{
if (scared)
{
score+=10;
ghostx[i]=7*blocksize;
ghosty[i]=7*blocksize;
}
else
{
dying=true;
deathcounter=64;
}
}
}
}
public void DrawGhost(int x, int y)
{
if (ghostanimpos==0 && !scared)
{
goff.drawImage(ghost1,x,y,this);
}
else if (ghostanimpos==1 && !scared)
{
goff.drawImage(ghost2,x,y,this);
}
else if (ghostanimpos==0 && scared)
{
goff.drawImage(ghostscared1,x,y,this);
}
else if (ghostanimpos==1 && scared)
{
goff.drawImage(ghostscared2,x,y,this);
}
}
public void MovePacMan()
{
int pos;
short ch;
if (reqdx==-pacmandx && reqdy==-pacmandy)
{
pacmandx=reqdx;
pacmandy=reqdy;
viewdx=pacmandx;
viewdy=pacmandy;
}
if (pacmanx%blocksize==0 && pacmany%blocksize==0)
{
pos=pacmanx/blocksize+nrofblocks*(int)(pacmany/blocksize);
ch=screendata[pos];
if ((ch&16)!=0)
{
screendata[pos]=(short)(ch&15);
score++;
}
if ((ch&32)!=0)
{
scared=true;
scaredcount=scaredtime;
screendata[pos]=(short)(ch&15);
score+=5;
}
if (reqdx!=0 || reqdy!=0)
{
if (!( (reqdx==-1 && reqdy==0 && (ch&1)!=0) ||
(reqdx==1 && reqdy==0 && (ch&4)!=0) ||
(reqdx==0 && reqdy==-1 && (ch&2)!=0) ||
(reqdx==0 && reqdy==1 && (ch&8)!=0)))
{
pacmandx=reqdx;
pacmandy=reqdy;
viewdx=pacmandx;
viewdy=pacmandy;
}
}
// Check for standstill
if ( (pacmandx==-1 && pacmandy==0 && (ch&1)!=0) ||
(pacmandx==1 && pacmandy==0 && (ch&4)!=0) ||
(pacmandx==0 && pacmandy==-1 && (ch&2)!=0) ||
(pacmandx==0 && pacmandy==1 && (ch&8)!=0))
{
pacmandx=0;
pacmandy=0;
}
}
pacmanx=pacmanx+pacmanspeed*pacmandx;
pacmany=pacmany+pacmanspeed*pacmandy;
}
public void DrawPacMan()
{
if (viewdx==-1)
DrawPacManLeft();
else if (viewdx==1)
DrawPacManRight();
else if (viewdy==-1)
DrawPacManUp();
else
DrawPacManDown();
}
public void DrawPacManUp()
{
switch(pacmananimpos)
{
case 1:
goff.drawImage(pacman2up,pacmanx+1,pacmany+1,this);
break;
case 2:
goff.drawImage(pacman3up,pacmanx+1,pacmany+1,this);
break;
case 3:
goff.drawImage(pacman4up,pacmanx+1,pacmany+1,this);
break;
default:
goff.drawImage(pacman1,pacmanx+1,pacmany+1,this);
break;
}
}
public void DrawPacManDown()
{
switch(pacmananimpos)
{
case 1:
goff.drawImage(pacman2down,pacmanx+1,pacmany+1,this);
break;
case 2:
goff.drawImage(pacman3down,pacmanx+1,pacmany+1,this);
break;
case 3:
goff.drawImage(pacman4down,pacmanx+1,pacmany+1,this);
break;
default:
goff.drawImage(pacman1,pacmanx+1,pacmany+1,this);
break;
}
}
public void DrawPacManLeft()
{
switch(pacmananimpos)
{
case 1:
goff.drawImage(pacman2left,pacmanx+1,pacmany+1,this);
break;
case 2:
goff.drawImage(pacman3left,pacmanx+1,pacmany+1,this);
break;
case 3:
goff.drawImage(pacman4left,pacmanx+1,pacmany+1,this);
break;
default:
goff.drawImage(pacman1,pacmanx+1,pacmany+1,this);
break;
}
}
public void DrawPacManRight()
{
switch(pacmananimpos)
{
case 1:
goff.drawImage(pacman2right,pacmanx+1,pacmany+1,this);
break;
case 2:
goff.drawImage(pacman3right,pacmanx+1,pacmany+1,this);
break;
case 3:
goff.drawImage(pacman4right,pacmanx+1,pacmany+1,this);
break;
default:
goff.drawImage(pacman1,pacmanx+1,pacmany+1,this);
break;
}
}
public void DrawMaze()
{
short i=0;
int x,y;
bigdotcolor=bigdotcolor+dbigdotcolor;
if (bigdotcolor<=64 || bigdotcolor>=192)
dbigdotcolor=-dbigdotcolor;
for (y=0; y<scrsize; y+=blocksize)
{
for (x=0; x<scrsize; x+=blocksize)
{
goff.setColor(mazecolor);
if ((screendata[i]&1)!=0)
{
goff.drawLine(x,y,x,y+blocksize-1);
}
if ((screendata[i]&2)!=0)
{
goff.drawLine(x,y,x+blocksize-1,y);
}
if ((screendata[i]&4)!=0)
{
goff.drawLine(x+blocksize-1,y,x+blocksize-1,y+blocksize-1);
}
if ((screendata[i]&8)!=0)
{
goff.drawLine(x,y+blocksize-1,x+blocksize-1,y+blocksize-1);
}
if ((screendata[i]&16)!=0)
{
goff.setColor(dotcolor);
goff.fillRect(x+11,y+11,2,2);
}
if ((screendata[i]&32)!=0)
{
goff.setColor(new Color(224,224-bigdotcolor,bigdotcolor));
goff.fillRect(x+8,y+8,8,8);
}
i++;
}
}
}
public void ShowIntroScreen()
{
String s;
goff.setFont(largefont);
goff.setColor(new Color(0,32,48));
goff.fillRect(16, scrsize/2 - 40, scrsize-32,80);
goff.setColor(Color.white);
goff.drawRect(16, scrsize/2 - 40, scrsize-32,80);
if (showtitle)
{
s="Java PacMan";
scared=false;
goff.setColor(Color.white);
goff.drawString(s,(scrsize-fmlarge.stringWidth(s)) / 2 +2, scrsize/2 - 20 +2);
goff.setColor(new Color(96,128,255));
goff.drawString(s,(scrsize-fmlarge.stringWidth(s)) / 2, scrsize/2 - 20);
s="(c)2000 by Brian Postma";
goff.setFont(smallfont);
goff.setColor(new Color(255,160,64));
goff.drawString(s,(scrsize-fmsmall.stringWidth(s))/2,scrsize/2 + 10);
s="b.postma@hetnet.nl";
goff.setColor(new Color(255,160,64));
goff.drawString(s,(scrsize-fmsmall.stringWidth(s))/2,scrsize/2 + 30);
}
else
{
goff.setFont(smallfont);
goff.setColor(new Color(96,128,255));
s="'S' to start game";
goff.drawString(s,(scrsize-fmsmall.stringWidth(s))/2,scrsize/2 - 10);
goff.setColor(new Color(255,160,64));
s="Use cursor keys to move";
goff.drawString(s,(scrsize-fmsmall.stringWidth(s))/2,scrsize/2 + 20);
scared=true;
}
count--;
if (count<=0)
{ count=screendelay; showtitle=!showtitle; }
}
public void DrawScore()
{
int i;
String s;
goff.setFont(smallfont);
goff.setColor(new Color(96,128,255));
s="Score: "+score;
goff.drawString(s,scrsize/2+96,scrsize+16);
for (i=0; i<pacsleft; i++)
{
goff.drawImage(pacman3left,i*28+8,scrsize+1,this);
}
}
public void CheckScared()
{
scaredcount--;
if (scaredcount<=0)
scared=false;
if (scared && scaredcount>=30)
mazecolor=new Color(192,32,255);
else
mazecolor=new Color(32,192,255);
if (scared)
{
screendata[7*nrofblocks+6]=11;
screendata[7*nrofblocks+8]=14;
}
else
{
screendata[7*nrofblocks+6]=10;
screendata[7*nrofblocks+8]=10;
}
}
public void CheckMaze()
{
short i=0;
boolean finished=true;
while (i<nrofblocks*nrofblocks && finished)
{
if ((screendata[i]&48)!=0)
finished=false;
i++;
}
if (finished)
{
score+=50;
DrawScore();
try
{
Thread.sleep(3000);
}
catch (InterruptedException e)
{
}
if (nrofghosts < maxghosts)
nrofghosts++;
if (currentspeed<maxspeed)
currentspeed++;
scaredtime=scaredtime-20;
if (scaredtime<minscaredtime)
scaredtime=minscaredtime;
LevelInit();
}
}
public void run()
{
long starttime;
Graphics g;
Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
g=getGraphics();
while(true)
{
starttime=System.currentTimeMillis();
try
{
paint(g);
starttime += 40;
Thread.sleep(Math.max(0, starttime-System.currentTimeMillis()));
}
catch (InterruptedException e)
{
break;
}
}
}
public void start()
{
if (thethread == null) {
thethread = new Thread(this);
thethread.start();
}
}
public void stop()
{
if (thethread != null) {
thethread.stop();
thethread = null;
}
}
}
