\ snake supported by a queue of emoji
\ 🐀🐁🐂🐃🐄🐅🐆🐇🐈🐉🐊🐋🐌🐍

const qlength=20;

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

procedure enqueue(x,y); \ queues the next emoji and its coordinates
  begin
    qemoji{tail}:=next;
    next:=next+1;
    if next>emojicount then
      next:=1;
    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; \ draw all emojis in queue
  var i;
  begin
    if tail#head then
      begin
        i:=head;
        call cvclear;
        while i#tail do
          begin
            call emojidraw(qemoji{i},qx{i},qy{i},20);
            i:=i+1;
            if i=qlength then
              i:=0            
          end
      end
  end;

procedure laserpoint;
  \ Line to the emoji closest to the cursor
  var i,mindist,minindex;

  procedure updatemin; \ checks queue element i for being closer
    var xdiff,ydiff,dist;
    begin
      xdiff:=cvx-qx{i};
      ydiff:=cvy-qy{i};
      dist:=xdiff*xdiff+ydiff*ydiff;
      if dist<mindist then
        begin
          mindist:=dist;
          minindex:=i
        end
    end;

  begin \ laserpoint
    call cvasclick;
    while cvclickx<0 do \ continue until click
      begin
        if cvx>0 then \ wait for cursor to be over canvas
          if tail#head then
            begin
              mindist:=999999;
              i:=head;
              while i#tail do
                begin
                  call updatemin;
                  i:=i+1;
                  if i=qlength then
                    i:=0         
                end;
              \ redraw canvas and draw line from cursor to closest
              call draw;
              call cvline(cvx,cvy,qx{minindex},qy{minindex})
            end;
        call wait(10);
      end;
    call draw
  end; \ laserpoint

begin
  next:=1;
  call cvasclick;
  while 1=1 do
    begin
      call cvclear;
      while cvx<0 do
        call wait(10);
      tail:=0;
      head:=0;
      while cvx>-1 do
        begin
          if cvclickx>-1 then
            begin
              call laserpoint;
              call cvasclick; \ to set up next stall
              call wait(500)  \ users are not real smooth with clicks
            end;
          call enqueue(cvx,cvy);
          call draw;
          call wait(200)
        end
    end
end.