Twenty-nine minutes is the last minute before a half hour, useful when the calendar says thirty and the walk to the next room takes one. Use the block for a single deliverable: a summary, a patch, a page.
If you need the full half hour, use the thirty minute timer instead of negotiating with this one. Press space to start or pause, R to reset, and F for fullscreen. The screen can stay awake after you start, using the wake lock your browser allows. Pick the alarm before you begin. A bell, a chime, a beep, or a short digital pulse all come from the Web Audio API, so there is no sound file to wait on.
This page is the 29 minutes countdown and nothing else is running underneath it. Related lengths are linked under the guide if you want a neighbor, and the timer itself stays above the fold.
Questions
How do I run a 29 minutes timer on a projector?
Press start, then F or the fullscreen button. Classroom mode hides the writing so the digits fill the wall. If you need the full half hour, use the thirty minute timer instead of negotiating with this one.
What is 29 minutes actually good for?
Twenty-nine minutes is the last minute before a half hour, useful when the calendar says thirty and the walk to the next room takes one.
Will the countdown drift if I switch tabs?
No. The end is a timestamp. The display is the gap between that timestamp and now, so a background tab does not lose seconds the way a ticking counter would.