We all love achievements in games, being rewarded for accomplishments as well. I'd like to pitch some more ideas for achievements in HN2 since there's not many that aren't story related. I'll list it out like a list and people can add feedback or their own in the comments...also they aren't in order so yeah. If people like this, I'll draw achievement icon concepts.
(SOME OF THESE WILL TAKE IDEAS FROM OTHER FEEDBACKS I HAVE.)
Animal Lover - The real question is, are you a dog or cat person?
How to unlock: Pet all animals that you can in the main game and in Back To School
Cutting The Knot - That's knot how it works!
How to unlock: Put in any code without fully solving the puzzle involving it (like putting in the safe code for otto's safe without putting up a single paper piece)
The 60's Rule! - Now, what's on them? (Secret Achievement)
How to unlock - Find all tapes in the main game and put them into the tape holders
Golden Ticket - I have a bad feeling about this. (Secret Achievement)
How to unlock - Get the golden apple coin in the fountain.
Book Return - Right on time!
How to unlock: Return all books to their bookcases in Late Fees
Knowledge Was Power - Beat Late Fees
Fetch! - Good dog!
How to unlock: Get the key from Gunter, or alternatively play fetch with Gunter 5 times
Better Times - Nostalgia hurts.
How to unlock: Observe the janitor alone in Late Fees
School's Out! - Beat Back To School (not late fees.)
(these two are kinda eh since idk how to feel about making hello copter achievements.)
High Altitudes - I can see my house from here!
How to unlock: Use hello copter and fly high outside (not to the top of the map, but still high regardless)
Yoink! - It's mine now!
How to unlock: Use the drone's grappling hook to grab a item.
that's all i can think of atm. let me know what you think in the comments.

