Need to Know - keep a surprise under wraps until the reveal

Keep one surprise - a party, a gift, a proposal, a trip - secret until the reveal. Free in the browser: three need-to-know rings for who is in on it, flags for children, housemates and people listed twice, a radio tuning dial of 14 shared channels that could give it away (calendars, joint cards, shopping accounts, parcels, group chats, lock screens and more) with a loudness estimate, a fuse to the reveal and exports including a calendar file. One metered task threat-models the secret: every leak with a risk and a plug, a verdict (airtight, patch the leaks, lockdown), briefs, six spy-style field rules, a cover-story check, a countdown and a fallback if the person gets suspicious. The page re-checks every plan. Built on @bobmatnyc/threat-modeling.