line(x1, y1, x2, y2, lineWidth, strokeStyle) {
    this._ctx.beginPath();
    this._ctx.lineWidth = lineWidth;
    this._ctx.strokeStyle = strokeStyle;
    this._ctx.moveTo(x1, y1);
    this._ctx.lineTo(x2, y2);
    this._ctx.closePath();
    this._ctx.stroke();
  }
Create a line
@param {number} x1
@param {number} y1
@param {number} x2
@param {number} y2
@param {number} lineWidth
@param {string} strokeStyle