Marioface5: KSP is a lot of fun! The last time I played, I think my best accomplishment was landing on Minmus and getting back from there. Or landing on Mun and getting back, since some people seem to consider that to be harder. I did Mun first though.
Yeah, I did the Mun first too, since it's a big, "heavy" target on the equatorial plane, it's so much easier to get there on instinct. Back then, adjusting my orbit to get an orbital rendez-vous with something as small as Minmus sounded like Voodoo magic. Getting to Mun was easy. It was landing safely, and then come back to Kerbin that was really tricky.
But when you really know how to use the flightpath planning tool (for me, it took the "asteroid redirect mission part 1" tutorial), Minmus with its weaker gravity is really sooo much easier.
Driving a rover there is a pain, though. They jump into orbit at the slightest bump, and my rovers tend to be pretty unstable even on the best conditions ^^
But yeah, it's an wonderful game. The sense of accomplishment when you realize your first orbit, when you stick your first rocket landing, when you reach the Mun, when you manage your first orbital rendez-vous with a stranded Kerbal, or when you dock your first space station... It's awesome. :)