There are three awesome milestones in KSP:
- Returning a surface sample from the mun
- Aerobraking and successfully landing on Duna
- Strap a spaceplane (or two for backup and easier mass balancing) to an interplanetary mothership bound for Jool. Then undock the spaceplane around Laythe, fly down and land on an island, and fly up again for docking.
I recently finished #3 in KSP2, and it feels even better there.
Best regards,
Proud kerbonaut since 2013