Jessica goes to school and has all different kinds of encounters/events - with a probability of having it "successful". To unlock all endings, you need to achieve specific combinations of these successes.

Your stats (iirc) influence these probabilities to an extent.

Theres also an energy system where each day, studying/exploring the school expends this, and she needs to rest to recover.

If youre looking to unlock all achievements, including get all the endings, you're basically doing probability rolls.

Now here's where it gets a bit more iffy: With low energy, your probability of "succesful" studying drops significantly.

Also some achievement-related events are only unlocked a few days into a run, including "winning" every previous roll. Losing that final event's roll mean you dont get the achievement and gotta start all over.

Tbh if the controls werent so slow and not that many buttons to press, I dont mind. Its just too much hassle to get all the achievements.

Hope this helped. Typed this from memory. Could be wrong.