This is based on the examples for transform-origin on MDN

css-transforms-1

css-transforms-2

#box17 { transform: matrix3d( 1.00, 0.00, 0.00, 0.00, 0.00, 0.50, -0.87, 0.00, 0.00, 0.87, 0.50, 0.00, 0.00, 0.00, 0.00, 1.00 ); transform-origin: 50% 50%; }

#box18 { transform: matrix3d( 0.50, 0.00, 0.87, 0.00, 0.00, 1.00, 0.00, 0.00, -0.87, 0.00, 0.50, 0.00, 0.00, 0.00, 0.00, 1.00 ); transform-origin: 50% 50%; }

#box19 { transform: matrix3d( 0.50, -0.87, 0.00, 0.00, 0.87, 0.50, 0.00, 0.00, 0.00, 0.00, 1.00, 0.00, 0.00, 0.00, 0.00, 1.00 ); transform-origin: 50% 50%; }

#box20 { transform: matrix3d( 0.25, -0.43, 0.87, 0.00, 0.81, -0.40, -0.43, 0.00, 0.53, 0.81, 0.25, 0.00, 0.00, 0.00, 0.00, 1.00 ); transform-origin: 50% 50%; }