text: class Counter
  {
      constructor(outputElem)
      {
          this.outputElem = outputElem;
          
          this.reset();
      }
  
      get counter()
      {
          return this._counter;
      }
  
      reset()
      {
          this._counter = 0;
          this.update();
      }
  
      increase()
      {
          if(this._counter == 9999) return false;
          this._counter++;
          this.update();
          return true;
      }
      
      decrease()
      {
          if(this._counter == 0) return false;
          this._counter--;
          this.update();
          return true;
      }
  
      update()
      {
          this.outputElem.textContent = this._counter;
      }
  }
  