Your challenge is to recreate and perform all elements of a (successful) Starship integrated flight test:
Build a two-stage heavy lift rocket, both stages capable of autonomous flight and propulsive landing.
Launch and begin flying your rocket to orbit... then quicksave.
Decouple and boost the first stage back to the launch site, landing it on one of the four landing pads. Use those gridfins!
Load the quicksave, fly the second stage to orbit, then deorbit it so that it re-enters over the ocean to the west of the KSC.
Propulsively slow the second stage's descent so that it splashes down in one piece. (Super bonus points if you also land the second stage on a KSC landing pad instead)
Good luck, kerbonauts!