Story & World
One way they could enter the world is to literally fall from the sky.
The player character starts off by restoring small pieces of the structures (platforms, pillars, interactable objects) to continue moving through the structures towards the generators.
Further in the story, objects will appear that are broken, but when the character tries to rebuild them, these objects crumble violently and cannot be repaired anymore. These objects represent a person’s resistances to the healing process or to the therapy.
Eventually, the character encounters a structure that crumbles violently when the player tries to Rebuild an object. At this point, the character must entirely Rebuild the structure.
This moment in the story represents the point where a person’s resistances are revealed to their fullest and only after they are broken can the healing process continue. This can also serve as the story’s climax.
The final level, the space tower, ends with the player reaching the portal in the uppermost dome. The portal launches them upwards towards the sky and the game ends.
Characters
The main character enters the world with the aim to bring it back to working order.
She carries a magical lute that when played restores and repairs things.
When reaching each of the structures' generator, she plays a short song on the lute that powers it.
I think we can have the main character have a bit more personality than just a silent robed character travelling for some mysterious reason.
She could have voice lines reacting to what she sees in the world.
The lute acts as an instrument and as a pet that follows the protagonist around.
When the character jumps off a platform, the lute can stay behind to mark the place for recalling until the character lands on a different platform and the lute can fly to her.