Rarfado

Rarfado trains one skill most people never practise: knowing how sure you really are. Instead of picking an answer, you drag ✋ two handles along a number 🔢 line and claim "I'm 90% sure it's between here and here." Then the true value drops onto the line as a pin. A narrow range that holds the truth scores high; a wide one or a miss scores less.

Every range feeds a live needle in the corner of the screen. If your "90% sure" ranges only catch the truth six times in ten, you'll see 👀 it straight away, along with a verdict: overconfident, well calibrated, or underconfident. The stretch coach replays your whole history ⏳ and works out exactly how much wider your ranges would need to be to mean what they say. You can turn that into a dashed guide on the rail for your next round.

There are more than 500 original questions about everyday quantities: animals, the human body, famous buildings, space, food 🍎, sport, weather 🌤️, technology and more. For quick true-or-false calls there's a Sure-o-meter with a confidence dial, scored by Brier score 🔢 and plotted on a calibration chart 📊. A daily ten gives everyone the same set of questions each day.

You can also write your own questions about real things at home, such as the beans in a jar or the weight of a pan, with an optional photo 📸, and hand the phone 📱 to a friend to see 👀 how honest their ranges are. Rarfado works fully offline 📴, keeps everything on your device, and asks for nothing but your guesses. Open Rarfado, set your first range, and find out how far your certainty can be trusted.