Изобразить траекторию движения пьяницы - Turbo Pascal

uses crt,dos,Graph;
const hor=100;ver=70;width=8;height=6;prob_factor=0.2;
var stolb:array[0..ver,0..hor] of 0..2;sh,x:integer;
    prob:real; ch:char; x_center:array[0..hor] of word;
    y_center:array[0..ver] of word; count,radius,page:word; ss:string;
 
procedure init_pian;
var j,k:word;
begin count:=0;
      for j:=0 to ver do
          for k:=0 to hor do
          begin
          if random<=prob then stolb[j,k]:=1
          else stolb[j,k]:=0;
          end;
          stolb[50,35]:=2;
          end;

procedure shag;
var j, k, prev_j, next_j, prev_k, next_k :word;
begin sh:=random(8)+1;
for j:=0 to ver do begin
if j=0 then prev_j:=ver else prev_j:=j-1;
if j=ver then next_j:=0 else next_j:=j+1;
for k:=0 to hor do begin
if k=0 then prev_k:=hor else prev_k:=k-1;
if k=hor then next_k:=0 else next_k:=k+1;
if stolb[j,k]=2 then begin
case sh of
1:if stolb[prev_j,prev_k]=0 then  begin
x:=stolb[j,k];stolb[j,k]:=stolb[prev_j,prev_k];
stolb[prev_j,prev_k]:=x;               end else break;
2:if stolb[prev_j,k     ]=0 then  begin
x:=stolb[j,k];stolb[j,k]:=stolb[prev_j,k     ];
stolb[prev_j,prev_k]:=x;end else break;
3:if stolb[prev_j,next_k]=0 then  begin
x:=stolb[j,k];stolb[j,k]:=stolb[prev_j,next_k];
stolb[prev_j,prev_k]:=x;    end else break;
4:if stolb[j    ,prev_k]=0 then  begin
x:=stolb[j,k];stolb[j,k]:=stolb[j     ,prev_k];
stolb[prev_j,prev_k]:=x;end else break;
5:if stolb[j    ,next_k]=0 then  begin
x:=stolb[j,k];stolb[j,k]:=stolb[j     ,next_k];
stolb[prev_j,prev_k]:=x;end else break;
6:if stolb[next_j,prev_k]=0 then  begin
x:=stolb[j,k];stolb[j,k]:=stolb[next_j,prev_k];
stolb[prev_j,prev_k]:=x;end else break;
7:if stolb[next_j,k     ]=0 then  begin
x:=stolb[j,k];stolb[j,k]:=stolb[next_j,k     ];
stolb[prev_j,prev_k]:=x; end  else break;
8:if stolb[next_j,next_k]=0 then  begin
x:=stolb[j,k];stolb[j,k]:=stolb[next_j,next_k];
stolb[prev_j,prev_k]:=x; end else break;
end;end;end;end;end;
 
procedure init_screen;
var GraphDriver,GraphMode:integer;j,k:word;
begin GraphDriver:=VGA;GraphMode:=VGAMed;
page:=0;InitGraph(GraphDriver,GraphMode,'');
if GraphResult<>grOK then halt;
for k:=0 to hor do
x_center[k]:=trunc(k*width) + (width div 2);
for j:=0 to ver do
y_center[j]:=(height div 2) +trunc(j*height);
radius:= 4;end;

procedure display;
var j,k:word;
 
procedure rule_plane;
var j,k:word;
begin setviewport(0,0,getmaxX,getmaxY, clipon);
      setfillstyle(solidfill,blue);
      bar(0,0,getmaxx,10);
      setcolor(white);
      outtext('Raz za razom: ');
      OutTextXY(250, 0, 'Q:Quit');
      OutTextXY(450, 0, 'Any other key: zanovo');
      str(count ,ss);outtext(ss);
      SetBkColor(DarkGray);
end;{rule_plane}

begin if count<>0 then shag;
inc(count);
page:=1-page;
setactivepage(page);cleardevice;
setcolor(yellow);
for j:=0 to ver do
for k:=0 to hor do
if stolb[j,k] =1 then circle(x_center[k],y_center[j],radius);
setcolor(green);
for j:=0 to ver do
for k:=0 to hor do
if stolb[j,k]=2 then circle(x_center[k],y_center[j],radius);
rule_plane;setvisualpage(page);end;{display}
 
begin init_screen;
repeat randomize;
       prob :=0.1+prob_factor*random;
       outtextXY(0,0,'pianica');
       writeln;
       outtextXY(0,15,'hodit randomno');
       outtextXY(0,30,'s veroiatnostiu  0.125');
       outtextXY(0,60,'press any key to start: ');
       ch:=readkey;
       cleardevice;init_pian;
       repeat
          display;
          if keypressed then
          begin ch:=readkey;
                break;
          end;
          until false;
          setviewport(0,0,getmaxX,getmaxY,clipon);
          cleardevice;
          setcolor(white);
          if upcase(ch) = 'Q' then break;
          until false;
          closeGraph;
end.