fun with a worm

const qlength=50;

var qx{qlength},qy{qlength},tail,head;

procedure enqueue(x,y);
  begin
    qx{tail}:=x;
    qy{tail}:=y;
    tail:=tail+1;
    if tail=qlength then
      tail:=0;
    if tail=head then
      begin
        head:=head+1;
        if head=qlength then
          head:=0
      end
  end;

procedure draw;
  var i;
  begin
    if tail#head then
      begin
        i:=head;
        call cvclear;
        while i#tail do
          begin
            call cvball(qx{i},qy{i},7);
            i:=i+1;
            if i=qlength then
              i:=0            
          end
      end
  end;

begin
  while 1=1 do
    begin
      call cvclear;
      while cvx<0 do
        call wait(10);
      tail:=0;
      head:=0;
      while cvx>-1 do
        begin
          call enqueue(cvx,cvy);
          call draw;
          call wait(10);
        end
    end
end.