ninety seconds, then go again.

Build me a rest timer as a single web page for use on my phone at the gym.

Ask me first:
- What rest lengths I use most, so they can be presets.
- Whether I want a simple countdown, an interval timer (work/rest/rounds), or both.
- What should happen at zero: a sound, a vibration, a colour change, or some combination.

Keep the interview to those. Do not invent intervals for a training style I did not describe.

WHAT IT DOES

- One screen. The countdown is the largest thing on it by a long way — readable at arm's length, sitting on a bench, in bad light.
- My presets are buttons along the bottom. Tapping one starts it immediately; there is no "set up timer" step.
- A big start/stop control and a reset. Tapping the countdown itself restarts the current preset, because that is the gesture I will reach for.
- At zero: play a short sound, vibrate if the browser allows it, and change the screen colour so it works with the sound off. Let me mute it.
- Interval mode, if I asked for it: work seconds, rest seconds, number of rounds, and a clear display of which round I am in.
- Add and edit presets in the page itself, and remember them for next time.
- Keep the screen awake while a timer is running if the browser supports it, and do not pretend to if it does not.

DESIGN

- Enormous numerals. Everything else small and out of the way.
- High contrast, works in a bright gym and a dark one.
- No animation except the countdown itself. Nothing that draws attention while I am mid-set.

BE HONEST ON THE PAGE

- Note that presets are stored in this browser only.
- Do not claim background timing, lock-screen controls, or notifications. A web page cannot do those reliably, and a timer that silently stops when the screen locks is worse than no timer — say that the page needs to stay open.
- Do not invent a training protocol or tell me how long to rest.

DELIVERY

- Produce one self-contained HTML file. Inline the CSS and JavaScript.
- No build step, no server, no framework, no package install, no external
  requests at runtime.
- Mobile-first and responsive; it has to be usable one-handed on a phone and
  still look right on a laptop.
- Accessible: semantic HTML, real contrast, visible keyboard focus, labelled
  controls, touch targets big enough to hit, and respect reduced-motion.
- Use placeholders where information is missing. Do not invent facts, numbers,
  names, dates, prices, or results I have not given you.
- Before you call it finished, use it yourself: enter real-looking data, reload
  the page, and confirm nothing is lost or mangled.

PUBLISHING

Publish the finished page to HTMLShare and give me the link.

Use exactly one of the two paths below, preferring the first. Make the call
directly. Do not route it through a code sandbox, container, or computer-use
session — that is where the request gets blocked, and it is never necessary.

1. An HTMLShare integration or connector, if you have one configured.
   The page is permanent and owned by my account. Report the url and the
   siteId. There is no claimUrl or manageToken on this path — do not go
   looking for one, and do not switch paths in order to produce one.

2. Otherwise, publish anonymously over REST. No account, key, or signup is
   needed:

    POST https://api.htmlshare.net/v1/publish
    content-type: application/json

    {"html": "<!doctype html> ... "}

   The reference is https://htmlshare.net/docs and, for the full schema,
   https://api.htmlshare.net/openapi.json

   Report these from the response, in your reply and never inside the page:
     url          the public page
     claimUrl     a private link that is mine alone. opening it is how I keep
                  the page past its 24-hour expiry, or set an email reminder
                  before it goes. it carries the manage token, so it must
                  never appear in the published HTML or anywhere a visitor
                  could see it.
     manageToken  the only thing that can edit or delete this page later. it is
                  returned once and never again, so tell me what it is.

Tell me which of the two you used. If the path you reach for first is
unavailable in your environment, say so and tell me what you are switching to
before you publish — a permanent page on my account and a 24-hour anonymous
page are different things, and which one I get is my decision, not a detail.

If I ask for a change afterwards, update the existing page instead of
publishing again, so the URL I have already shared keeps working — through the
same integration on path 1, or with the manage token as an X-Manage-Token
header on path 2.

RECIPE MARKER

Include this tag in the <head>, exactly as written:

    <meta name="htmlshare-recipe" content="rest-timer">

It tells htmlshare which recipe the page came from, so the library can count
that this one was actually made. It carries nothing else.