Update 2025: last update was in '22, sound stopped working for me around late '23, so be mindful if you have a multi-monitor setup because you might miss the pop-up alerting you to the time being up.
Still shows the time remaining in the icon though, so works for my use case and I hope it keeps working still even if abandoned by dev.

It's great exept for volume control, for some reason it works in the extention window but not when the actual alarm popup window triggers.. also is it supposed to pop up a new window instead of a notification? I don't mind but it was a surprise. My FF is v106.0.2 (64-bit) on windows if that helps.
Love that you can keep clicking the timer buttons to keep adding that time to the counter!

Useful, but there's margin for improvement.
Just some ideas:

- The remaining overlay always shows the time left in the first timer (the leftmost tb in timer selection), it should be possible to decide which time shall be displayed (i.e. a particular tab or the shortest remaining time)
- Different colors for each timer?
- Snooze alert button

Thanks for your work & attention