code: public static final Mat4 ortho2d(final float left, final float right, final float bottom, final float top) {
  		final float m00 = 2f / (right - left);
  		final float m11 = 2f / (top - bottom);
  		final float m22 = -1f;
  		final float m30 = - (right + left) / (right - left);
  		final float m31 = - (top + bottom) / (top - bottom);
  		
  		return new Mat4(
  				m00, 0f, 0f, 0f, 
  				0f, m11, 0f, 0f, 
  				0f, 0f, m22, 0f, 
  				m30, m31, 0f, 1f
  		);
  	}
docs: Creates a 2D orthographic projection matrix.  This method is analogous to the now
  deprecated {@code gluOrtho2D} method.
  
  @param left left vertical clipping plane
  @param right right vertical clipping plane
  @param bottom bottom horizontal clipping plane
  @param top top horizontal clipping plane
  @return