On: Why it's so challenging to land upright on the moo...

[0_____0]

The aviators might say - a good landing is one you walk away from.

How exactly do you define a successful landing? What if you're upright but all four legs collapsed and the spacecraft crushed your primary science payload?

[electroly → 0_____0]

A great landing is when you can use the plane again afterwards.

[ta1243 → 0_____0]

"Walk away from" would be "Primary payload can function (or at least not fail because of an action of the lander)"