code: func (m Matrix) ScaledXY(around Vec, scale Vec) Matrix {
  	m[4], m[5] = m[4]-around.X, m[5]-around.Y
  	m[0], m[2], m[4] = m[0]*scale.X, m[2]*scale.X, m[4]*scale.X
  	m[1], m[3], m[5] = m[1]*scale.Y, m[3]*scale.Y, m[5]*scale.Y
  	m[4], m[5] = m[4]+around.X, m[5]+around.Y
  	return m
  }
docs: // ScaledXY scales everything around a given point by the scale factor in each axis respectively.