the boring app.

Your phone is hard to put down. You pick it up without deciding to, open something, set it down, then reach for it again a minute later.
That is not really a decision anymore. It is a habit, and habits run on payoff. Most times you check, something is waiting: a message, a new post, something you haven't seen. Rewards that arrive unpredictably are the kind that stick hardest, which is how checking became a reflex you barely notice.
This app takes the payoff out of that moment. You pick which apps to block. When you go to open one, you come here first and solve a math problem. It is dull, it costs a little effort, and it gives you nothing back. The reflex still fires, but it meets a small wall instead of a reward, and a reflex that stops paying off slowly loses its grip.
The cost also rises the more you lean on it. Unlock once and the gate is short; come back again the same day and it asks for more problems and gives less time. Leaning on it harder will make the app push back.
You can set locked hours, when the blocked apps do not open at all and there is no problem that will let you in. Strict mode protects that: while a locked window is running, you cannot quietly widen your list, trim your hours, or shut the app off without solving your way through first.
The watch app can remind you when a block is lifted, so a few earned minutes do not quietly turn into an hour.
No accounts, no sign-in, no email, no data leaving your phone. Boring.