Learning Midnight: nothing goes public by accident

I'm a self-taught enthusiast poking around the Midnight Network, and I wanted to write down one thing that finally clicked for me this week. Maybe it helps someone else who's just starting out.
Midnight is a privacy blockchain, and you write its smart contracts in a language called Compact. Coming in, I assumed "privacy blockchain" meant everything is hidden by default and you flip a switch when you want to share something.
It's actually the other way around, and that surprised me.
In Compact, anything you want to put into the public, on-chain state you have to mark on purpose, with a keyword called disclose(). If you forget, the compiler stops you. It won't let you publish a value unless you've clearly said "yes, I mean to make this public."
The first time I hit that, it felt annoying, like extra typing for no reason. Then it clicked: that IS the privacy model. Nothing leaks by accident. You go line by line and decide exactly what crosses from the private side to the public side. Everything you don't disclose just stays private.
That made Midnight's whole "choose what you share, nothing more" idea real for me in a way the tagline never did.
To play with it, I built a tiny app: a proof-of-age gate. You prove you're over 18 without ever showing your birth year. The birth year stays private the whole time; the only thing that becomes public is a simple "yes, this person qualifies." Same idea, share the one fact that matters and keep the rest to yourself.
Still very early in my journey, but this one stuck with me. Most of what I picked up came straight from the docs at docs.midnight.network.
Repo, if you want to peek: https://github.com/tomiin/midnight-proof-of-age