anchor.diff:              brush
                 ..pos.x = x
                 ..pos.y = y
  -              ..prevPos.x = x
  -              ..prevPos.y = y
  +//              ..prevPos.x = x
  +//              ..prevPos.y = y
                 ..pressed = true;
   
               var color = querySelector('#color').text;
  
positive.code:               client.send(Message.changeColor, brush.color);
              }
  
              _drawPoint(x, y, brush.size, brush.color);
              client.send(Message.drawPoint, brush.pos.toJson());
  
              timer?.cancel();
              timer = new Timer.periodic(brushInterval, (_) {
                if (brush.moved) {
                  _drawLine(brush.prevPos.x, brush.prevPos.y, brush.pos.x,
                      brush.pos.y, brush.size, brush.color);
                  client.send(Message.drawLine, brush.pos.toJson());
  
                  brush
                    ..prevPos.x = brush.pos.x
                    ..prevPos.y = brush.pos.y
                    ..moved = false;
                }
              });
  
negative.code: 
          brush
            ..pos.x = pos.x
            ..pos.y = pos.y;
  
          _drawPoint(brush.pos.x, brush.pos.y);
        })
        ..on(Message.drawLine, (String json) {
          var pos = new Point.fromJson(json);
  
          brush
            ..pos.x = pos.x
            ..pos.y = pos.y;
  
          _drawLine(brush.pos.x, brush.pos.y);
        })
        ..on(Message.clearDrawing, (_) {
          _clearDrawing();
  