What is the focus timer?
The focus timer is one of NumLM’s time tools with a built-in focus environment: a scenery theme for full-screen mode and an ambient-sound mixer. Noise, fan and heartbeat sounds are synthesised in your browser; rain, wind, waves, fire, stream, crickets, birds and cafe are short studio-generated loops of about 300 KB each, fetched only when you switch them on and kept for offline use. There is no time limit and nothing to sign up for. Your mix and theme are remembered on this device and carry over to the timer, Pomodoro and interval tools.
25/5 with sound only in the focus block
This is the Pomodoro engine with the focus environment switched on: 25 minutes of focus with brown noise, a 5-minute break at 30 % volume, a 15-minute long break after four cycles. The break starts by itself; the next focus block waits for Start so you decide when to dive back in, and the sound fades in with it. Change the lengths in the panel if 50/10 or 90/20 suits you better.
Why the sound dips instead of stopping
A hard cut at every break is itself an interruption; a two-second slide to 30 % keeps the room’s character while making the break feel different, and the slide back up marks the start of work without an extra alarm. If you would rather keep the full level through breaks, turn off “Lower to 30 % on breaks”: the mix then plays on unchanged. For a silent break, press M (Stop sound) when it starts and M again when you get back to work.
Sounds that play only while you focus
With the timer link on, the mix follows the timer: it fades out one and a half seconds before the alarm, so the alarm is never buried under rain, and in the Pomodoro and Focus timers it drops to 30 % during breaks and comes back when the next focus block begins; pausing keeps the sound by default, and you can change both in the panel.
Switching a sound on plays it at once, timer or not; the link only shapes the level. Switch it off and the sound ignores the timer entirely, except that an alarm still dips it. On the white-noise and rain pages there is no link.
Background tabs, phones and iPhone
On a computer the sound keeps playing when you switch tabs: browsers do not throttle a tab that is producing audible sound, and the fade-outs are scheduled on the audio clock ahead of time. Android phones keep playing with the screen on; iPhone Safari pauses web audio when the screen locks, so keep the tab on screen and leave Keep screen on enabled (it is on by default on phones).
Themes, full screen and battery
Three themes are free (night library, rainy window, forest) and five more come with the beta pack. In the page the theme only tints the timer card; press F or the full-screen button and the scene fills the screen behind the ring, darkened so the digits stay readable. The images are still pictures — no video loops — and the optional drifting motes are off by default and stop whenever the tab is hidden or your system asks for reduced motion, which keeps the page light on laptops and phones.
Share a mix, save it, and the beta pack
Copy mix link puts your sounds and theme into the address (`?amb=rain:60,wind:20&th=night-library`), so a friend opens the same setup with one click. Logging in unlocks the beta pack: nine more sounds (waves, campfire, stream, crickets, birds, cafe murmur, fan, air conditioner, heartbeat), five more themes, a theme that follows the time of day, and named mixes. The free sounds and themes stay free; the pack only adds. Listening tip: keep the device volume at or below 60 % for long sessions.