Let's say there is a virtual digital pet, who is aging, as a computer simulation. And there is one flying computer, launched from far way, which is now close to the earth and is moving away from the earth to a star. There is another flying computer moving toward the earth from the star. Those 2 flying computers both are in 0.9c speed.
The earthlings upload this digital pet to the computer moving away from the earth, when it is close to the earth. Then it flies 100 LY away from the earthling's view. At that place, it encounters the other computer moving toward the earth. The virtual pet, now who is a little aged, is copied to the computer moving toward the earth. Sometime later, this computer finally gets close to the earth again. The earthlings download the virtual pet, and check its age.
Now, who is older? The earthlings or the virtual pet? It's easy to say, the computers flied fast and their time delayed. But from the virtual pet's view, the earthlings always moved at very fast speed, though the direction changed. Did the earthlings' time delay? How can we explain this version of twin paradox? I think this captures the essence of twin paradox. There is no acceleration and no gravity.
I know this is really similar to 2 clocks and synchronizing version of twin paradox. But in this way, I think we can clearly see the traveling one also as another independent observer.