docs: function (color) {
      if (color === undefined) {
        this.context.fillRect(0, 0, this.canvas.width, this.canvas.height);
      } else {
        let fillstyle = this.context.fillStyle;
        this.fillStyle(color);
        this.context.fillRect(0, 0, this.canvas.width, this.canvas.height);
        this.fillStyle(fillstyle);
      }
    }