code: public Matrix3x2f rotation(float angle) {
          float cos = (float) Math.cos(angle);
          float sin = (float) Math.sin(angle);
          m00 = cos;
          m10 = -sin;
          m20 = 0.0f;
          m01 = sin;
          m11 = cos;
          m21 = 0.0f;
          return this;
      }
docs: Set this matrix to a rotation matrix which rotates the given radians.
  <p>
  The resulting matrix can be multiplied against another transformation
  matrix to obtain an additional rotation.
  <p>
  In order to apply the rotation transformation to an existing transformation,
  use {@link #rotate(float) rotate()} instead.
  
  @see #rotate(float)
  
  @param angle
  the angle in radians
  @return this