Just basically awesome
The more I think about this, the more difficult I realise it is...
First, there's all the rocket science which is, well, rocket science. So very difficult.
Then there's the turning it round in space.
Then there's the aiming it at the right spot.
Then there's adjusting for Earth's rotation.
Then there's the bringing it back through the atmosphere.
Then there's the actually slowing enough to land without smashing.
Then there's the landing.
Then there's the refurbishing.
And all of this had to be thought up and designed and amended and refined even before a single piece of metal was bent in a complicated way.
This has got to be the achievement of the century, if not the millennium.