Kerbal Space Program is a physics game. That's a term that has been roundly abused and misrepresented, however. Does a mug on a desk fly off when you shoot it? Physics! Does your character fall down stairs like a ragdoll? Physics! Can you twang circular birds at pigs hiding in rickety wooden structures? Yay! Physics! As far as games are concerned, "physics" is now basically shorthand for "stuff that moves kind of realistically".