Temvo

Temvo starts from the idea that most people think they know what ten seconds feels like and almost nobody does. Each day's challenge is five rounds, the same for every player, and you get one shot at them before sharing your result and keeping your streak.

The rounds come from its disciplines. In Guess you watch a hidden timer and say how long it ran. In Hit you start the clock and stop it on a target time. Echo plays an interval for you to reproduce, and Tempo gives a beat to lock onto and then hold after it goes silent. In 9.99 you stop the timer on 9.99 seconds with the last seconds blurred out. A newer discipline, Edge, asks which of two tones was longer.

Each round scores 0 to 100 on how close you land, measured in proportion to the target, so a small miss on a short time counts as much as a bigger one on a long time. Results are timed to the hundredth of a second, and a leaderboard ranks the day's players. Outside the daily run, every discipline is open for practice, and Rooms lets a group face the same challenge live.

The five scores add up to a total out of 500. A full 100 is kept for a dead-on hit, so anything a hair off caps at 99. Your streak and bests stay on your device. Signing in with Google is optional and only puts a name beside your run on the board.

It plays in a browser with no account and takes about two minutes. The screens come in English, Spanish, French, German, Portuguese and Japanese. The site also has guides on how the brain times intervals.