code: public Matrix4f rotationTowardsXY(float dirX, float dirY) {
          if ((properties & PROPERTY_IDENTITY) == 0)
              MemUtil.INSTANCE.identity(this);
          this._m00(dirY);
          this._m01(dirX);
          this._m10(-dirX);
          this._m11(dirY);
          _properties(PROPERTY_AFFINE | PROPERTY_ORTHONORMAL);
          return this;
      }
docs: Set this matrix to a rotation transformation about the Z axis to align the local <code>+X</code> towards <code>(dirX, dirY)</code>.
  <p>
  The vector <code>(dirX, dirY)</code> must be a unit vector.
  
  @param dirX
  the x component of the normalized direction
  @param dirY
  the y component of the normalized direction
  @return this