I tried an hour or so and gave up, my general take is the developer took on more than he can chew. The game mechanic is extremely convoluted riddled not only with programming bugs but story logic ones too - multiple junctures where players are just left hanging not knowing what to do next.
The inability to overwrite save is ridiculous for a Renpy game, I take it as evidence that the developer modified the basic Renpy architecture so much that even a simple save function is broken.
Reminds me of the abandoned Deviant Anomalies, grand plans that the developer has but obviously lacks the resources and competency to execute. Quite a waste as I like the concept, story and nice graphics which I would have played happily in just a simple AVN format.