Space X almost landed a rocket on a floating platform. By almost we mean it blew up in a huge fireball, but actually, that's not bad at all.
Consider this: You're sending a huge rocket into space. You then want to have it launch its payload, fall back to Earth and then land itself (right way up) on the ground.
If that wasn't complex enough Space X decided they'd make it even more difficult by turning the ground into a floating platform in the middle of the ocean.
This then is about the positives. Not only did the rocket successfully re-enter without breaking up, the 14-story-tall Falcon 9 rocket then managed to find its target and successfully re-ignite its landing boosters.
As you can see however, the end result was sadly less fortuitous. The rocket's stabilising fins loose power and the rocket tilts over to a 45-degree angle at which point it hits the platform hard in what Elon Musk rather light-heartedly calls a RUD (Rapid Unscheduled Event).