{> Cut here. FileName= PLASMAT.PAS }
{$N+,X+,R-,S-,I-,G+,E+,Q-}
program plasma_tunnel;
uses crt,dos;
const segA000 : word = $A000;
      biosseg : word = $0040;
var v,pic : pointer;
    addr,x,y : word;
    i,r,d : byte;
    ds,rs : shortint;
    len : real;
    warp,interactive : boolean;
    keys : array[0..127] of boolean;
    oldint9h : procedure;
    key : char;
    stab : array[0..255] of byte;

procedure newint9h;interrupt;assembler;
asm
   xor bh,bh
   in al,60h
   mov bl,al
   and bl,01111111b
   xor al,10000000b
   shr al,7
   mov byte ptr keys[bx],al
   pushf
   call oldint9h
   cli
   mov es,biosseg
   mov ax,es:[1Ah]
   mov es:[1Ch],ax
   sti
end;

function vinkel(x,y : real) : byte;
var v : integer;
begin
   if (x = 0) and (y > 0) then vinkel := 64 else
   if (x = 0) and (y <= 0) then vinkel := 192 else
   begin
      v := round(arctan(y/x)/pi*128);
      if (x < 0) and (y < 0) then vinkel := v+128 else
      if (x < 0) and (y >= 0) then vinkel := 128+v else
      vinkel := v;
   end;
end;

function max(a,b : integer) : integer;
inline($58/$5B/$3B/$C3/$7F/$01/$93);
function min(a,b : integer) : integer;
inline($58/$5B/$3B/$C3/$7C/$01/$93);

procedure plasma(x1,y1,x2,y2 : longint);
var nx,ny : word;
    c : integer;

function cc(c,n : integer) : byte;
var d : integer;
begin
   d := ((x2-x1+y2-y1)*5) div 3;
   cc := min(max((c+d-random(d+d)) div n,1),255);
end;

procedure putpixel(x,y : byte;c : byte);assembler;
asm
   mov es,word ptr [pic+2]
   mov bl,x
   mov bh,y
   mov al,c
   mov es:[bx],al
end;

function getpixel(x,y : byte) : byte;assembler;
asm
   mov es,word ptr [pic+2]
   mov bl,x
   mov bh,y
   mov al,es:[bx]
end;

begin
   if ((x2-x1) < 2) and ((y2-y1) < 2) then exit;
   nx := x1+(x2-x1) shr 1;
   ny := y1+(y2-y1) shr 1;
   if getpixel(nx,y1) = 0 then
     putpixel(nx,y1,cc(getpixel(x1,y1)+getpixel(x2,y1),2));
   if getpixel(nx,y2) = 0 then
     putpixel(nx,y2,cc(getpixel(x1,y2)+getpixel(x2,y2),2));
   if getpixel(x1,ny) = 0 then
     putpixel(x1,ny,cc(getpixel(x1,y1)+getpixel(x1,y2),2));
   if getpixel(x2,ny) = 0 then
     putpixel(x2,ny,cc(getpixel(x2,y1)+getpixel(x2,y2),2));
   if getpixel(nx,ny) = 0 then
     putpixel(nx,ny,cc(getpixel(x1,y1)+getpixel(x2,y2)+
                       getpixel(x1,y2)+getpixel(x2,y1),4));
   plasma(x1,y1,nx,ny);
   plasma(nx,y1,x2,ny);
   plasma(x1,ny,nx,y2);
   plasma(nx,ny,x2,y2);
end;

procedure retrace;assembler;
asm
   mov dx,3DAh
@loop:
   in al,dx
   test al,8
   jnz @loop
@loop2:
   in al,dx
   test al,8
   jz @loop2
end;

procedure setp(c,r,g,b : byte);assembler;
asm
   mov dx,3C8h
   mov al,c
   out dx,al
   inc dx
   mov al,r
   out dx,al
   mov al,g
   out dx,al
   mov al,b
   out dx,al
end;

function test8086 : byte;assembler;
asm
   xor dl,dl
   push sp
   pop ax
   cmp sp,ax
   jne @out
   inc dl
   pushf
   pop ax
   or ax,4000h
   push ax
   popf
   pushf
   pop ax
   test ax,4000h
   je @out
   inc dl
@out:
   mov al,dl
end;

begin
   randomize;
   if test8086 < 2 then begin
      writeln('Sorry, you need a 386 or better to run this program.',#7);
      halt;
   end;

   interactive := false;
   write('Do you want to control? ');
   repeat
      key := readkey;
   until (upcase(key) in ['Y','N']);
   writeln(key);
   if upcase(key) = 'Y' then interactive := true;

   write('Wait while calculating tunnel data...');

   for i := 0 to 127 do keys[i] := false;
   for i := 0 to 255 do stab[i] := round(sin(i*pi/128)*127.5+127.5);

   getmem(v,64000);
   addr := 0;
   for y := 0 to 99 do
      for x := 0 to 319 do begin
         len := sqrt((x-159.5)*(x-159.5)+(y-99.5)*(y-99.5))+1;
         memw[seg(v^):addr] := vinkel(x-159.5,y-99.5)+
                               (round(4000/len) and 255) shl 8;
         inc(addr,2);
      end;


   getmem(pic,$FFFF);
   asm
      mov es,word ptr [pic+2]
      xor di,di
      mov cx,0FFFFh/4+1
      db 66h;xor ax,ax
      db 66h;rep stosw
   end;

   plasma(0,0,256,256);

   addr := 0;
   for y := 0 to 255 do
   for x := 0 to 255 do begin
      mem[seg(pic^):addr] :=
           (mem[seg(pic^):addr+256]+mem[seg(pic^):addr+256]+
              mem[seg(pic^):addr-256]+mem[seg(pic^):addr+1]+
              mem[seg(pic^):addr-1]) div 5;
      inc(addr);
   end;

   asm
      mov ax,13h
      int 10h
   end;

   for i := 1 to 63 do setp(i,i,32,32+i div 2);
   for i := 0 to 63 do setp(i+64,63-i,32+i div 2,63);
   for i := 0 to 63 do setp(i+128,i div 2,63-i,63-i);
   for i := 0 to 63 do setp(i+192,32+i div 2,0,i);

   getintvec($09,@oldint9h);
   setintvec($09,@newint9h);

   asm
      mov ax,word ptr [v+2]
      db 8Eh;db 0E0h {mov fs,ax}
      mov ax,word ptr [pic+2]
      db 8Eh;db 0E8h {mov gs,ax}
      mov es,segA000
   end;

   rs := 0;
   if not interactive then ds := 8;

   repeat
      if interactive and not warp then begin
         if keys[$48] then begin
            if ds < 10 then inc(ds);
         end else if ds > 0 then dec(ds);
         if keys[$50] then begin
            if ds > -10 then dec(ds);
         end else if ds < 0 then inc(ds);
         if keys[$4D] then begin
            if rs < 10 then inc(rs);
         end else if rs > 0 then dec(rs);
         if keys[$4B] then begin
            if rs > -10 then dec(rs);
         end else if rs < 0 then inc(rs);
      end else begin
         if not warp then r := stab[i];
         inc(i);
      end;

      inc(d,ds shr 1);
      inc(r,rs shr 1);

      if keys[1] then warp := true;
      if warp then begin
         inc(ds,2);
         inc(rs,1);
      end;

      retrace;

      asm
         push bp
         xor di,di
         xor bx,bx
         mov cl,r
         mov ch,d
         mov bp,8000

      @dloop:
         db 64h;mov dx,[bx]
         add dl,cl
         add dh,ch
         mov si,dx
         db 65h;mov al,[si]
         db 64h;mov dx,[bx+2]
         add dl,cl
         add dh,ch
         mov si,dx
         db 65h;mov ah,[si]
         db 66h;shl ax,16
         db 64h;mov dx,[bx+4]
         add dl,cl
         add dh,ch
         mov si,dx
         db 65h;mov al,[si]
         db 64h;mov dx,[bx+6]
         add dl,cl
         add dh,ch
         mov si,dx
         db 65h;mov ah,[si]
         db 66h;rol ax,16
         db 66h;stosw
         add bx,8
         dec bp
         jnz @dloop

         mov bp,8000
         sub bx,2
         add cl,128

      @dloop2:
         db 64h;mov dx,[bx]
         add dl,cl
         add dh,ch
         mov si,dx
         db 65h;mov al,[si]
         db 64h;mov dx,[bx-2]
         add dl,cl
         add dh,ch
         mov si,dx
         db 65h;mov ah,[si]
         db 66h;shl ax,16
         db 64h;mov dx,[bx-4]
         add dl,cl
         add dh,ch
         mov si,dx
         db 65h;mov al,[si]
         db 64h;mov dx,[bx-6]
         add dl,cl
         add dh,ch
         mov si,dx
         db 65h;mov ah,[si]
         db 66h;rol ax,16
         db 66h;stosw
         sub bx,8
         dec bp
         jnz @dloop2

         pop bp
      end;
   until ds >= 120;

   asm
      mov ax,3h
      int 10h
   end;

   setintvec($09,@oldint9h);
end.