Estimania

Estimania asks you to guess numbers rather than recall exact facts. Every day at midnight UTC a new set of five questions appears, spanning science, geography, history, music, sport and more. Some are Fermi questions in the spirit of the physicist's back-of-the-envelope problems, such as how many piano tuners work in Chicago, where nobody knows the exact answer but reasoning gets you close. Others are trivia with a number for an answer, such as how many studio albums a well known rapper has released.

Each answer scores from 0 to 100 points based only on the ratio between your guess and the reference value: points = 100 times (1 minus the absolute base-10 log of guess divided by answer). A perfect guess scores 100, being off by a factor of 2 scores 70, and being off by a factor of 10 or more scores nothing. Guessing too high and too low by the same factor costs the same. Each question shows its unit under the answer box, and a puzzle locks once you have played it.

After five questions you see your total out of 500 and where you rank on the day's leaderboard, which also has week and month views and shows players' streaks. You can create or join a friend group to compare scores question by question, link a second device with a recovery code, and play yesterday's set if you missed it. No sign-up is needed: you pick a nickname, and players can suggest their own questions.

Estimania is made by Valentin Forster, a solo developer in Graz, Austria, as a passion project with no ads, supported by donations on Ko-fi. It can be added to a phone's home screen as a web app. It suits Fermi problem fans, quiz players who like reasoning over memory, and anyone who wants to train a feel for scale.