My first version was 0.16 (2012). Of course back then it wasn't on Steam, so I don't know how many hours I've got. I'm sure Das & EJ have more, but I've got... many. And since I don't use Steam, I've got nearly every patch release saved as a stand alone game. I hope Take Two doesn't implement DRM.
Sorry for all these pix, I just wanted to share what early KSP was like. Kids these days, they don't know how good they've got it.
Clicking Start Game took you directly to the Space Center. There was no option to load previous saves... no Save Game system at all. You could only do Quick Saves.
Space Center: SPH, VAB, Launch Pad, Tracking Station. This was the only viewpoint, no ability to move the camera in this scene. Upgrading facilities was not a thing yet.
Vehicle Assembly Building: You can see the launch pad through the door which is East... same as the current version. However back then, the default orientation of a new craft inside the VAB was dorsal side facing West instead of South. But when you went to the launch pad the dorsal side would automatically orient South like the current version.
Space Plane Hangar: I didn't remember that the SPH was also labeled as VAB (see top of parts list panel). Btw, that first tab of parts was already selected by default when entering the VAB or SPH.
Tracking Station: This image is interesting because of what it does not show. Hint... camera is fully zoomed out.
Launch Pad: No flag pole, but check out that launch tower. It had no function, just eye candy. There were launch clamps in the game, they looked the same as today. And like the current version, rockets would launch fine without clamps. In case you can't read the Kerbal names, those are indeed our beloved Jeb, Bill, and Bob. Sorry Val, back then it was strictly a boys club.
Mun Mission: The staging list displayed fuel draining for each individual fuel tank. So each of those 4 boosters had two tanks. When the first tank was empty, a new fuel indicator appeared for the next tank.
Booster Jettison: I'm sure most of you have heard, back then the atmosphere model was very different. To get into orbit you had to go straight up to 10k altitude before starting your tilt to the East. If you tilted too soon, reaching orbit was a struggle. I am tilting to the East here, but there was no control authority for the roll... despite having SAS on. So you just had to ride it out.
Reaching Orbit: The basics of getting into orbit was the same... push your Apoapsis above 70k, cut throttle and coast, start burning again at the Ap. Like I mentioned before, there were no upgrades. So you got patched conics right off the bat (blue trajectory line). But maneuver nodes were not yet in the game. Another quality of life feature not yet added... no right clicking the Ap & Pe to lock the display on screen. Notice on the navball, you'll see the pink "Y" marker for Anti Target. However there was no function yet to be able to set anything as target... like the Mun. Also concerning the navball, there were neither Normal/Anti Normal, nor Radial In/Out markers.
Circularizing: Manual flight was very "exciting". To orient the ship, you first had to turn off SAS. If you left SAS on, pressing WASDQE did nothing. RCS was in the game, but we had little use for it as there was no docking function yet. Also missing from the game was any requirement for electric charge.
Patched Conics: Yes we did have patched conics, but there was no option to display anything beyond the first encounter. So to see the predicted trajectory back to Kerbin, you first would have to get into the Mun's SOI.
Obligatory Screenshot: No planting flags, EVA reports, surface samples or science of any kind. And of course there was no contract system. On the bright side, we did have jetpacks.
False Reentry: So for this attempt I set my Periapsis at 33k, which in the current version is a safe altitude for reentering from Mun distance. However with the old atmosphere model it was not low enough. I skipped off and went back into space. Reentry heating FX were not yet added. Also no function for physical time warp (if you're below 70k time warp is disabled). The next attempt I set the Pe to 20k, which worked perfectly with no issues.
Home Safe: Chutes were very forgiving back then. No worries that you were going too fast. There was no semi deployed state, or chute settings of any kind. You could stage the chutes 100 meters above the water (or land), and they would instantly be fully deployed. You can see above that during that first reentry attempt, Jeb as usual was having a great time. Bob was terrified, and Bill was in shock. I thought it was funny that as soon as I popped the chute, they were all in shock.
So I hope you enjoyed this trip down memory lane, as well as the partial list of game features we didn't have. But we sure had fun with what we did have.