the repayment, and what changes it.

Build me a mortgage calculator as a single web page. Show the working.

Ask me first:
- My currency.
- Whether I want repayment, interest-only, or both.
- Whether to model overpayments — regular, one-off, or both.
- Whether I want to compare two scenarios side by side.
- Whether the page should remember my inputs in this browser or forget them.

Do not prefill a rate as though it were a market figure. If you supply a starting value, label it clearly as an arbitrary placeholder.

WHAT IT DOES

- Inputs: amount borrowed, annual interest rate, term. All visible, all editable, nothing hidden in the code.
- Outputs, all at once: monthly repayment, total repaid, and total interest. Give the total interest the same visual weight as the monthly figure — it is the number lender calculators bury.
- A full amortisation schedule, at least by year and expandable to months: payment, interest, principal, remaining balance.
- Overpayments: a regular monthly extra, a one-off lump sum, or both, showing the effect on the term and on total interest. This is the most useful thing on the page.
- If I asked for comparison: two scenarios side by side with the differences stated as numbers.
- Recalculate as I type, so I can see which input the answer is sensitive to.

WHAT IT MUST NOT DO

- Do not fetch rates, indices or any market data. No network requests.
- Do not recommend a product, a lender, a term, or a strategy.
- Do not imply the figures are an offer, a quotation, or what anyone will actually lend.

DESIGN

- Inputs and results on one screen on a laptop so cause and effect are visible together.
- Monospace numbers, aligned columns, currency formatted consistently.
- The amortisation table should be readable and scrollable rather than crammed.

BE HONEST ON THE PAGE

- State what the calculation excludes: rate changes after any fixed period, arrangement and valuation fees unless I entered them, insurance, tax, and early repayment charges.
- State that it is arithmetic on figures I supplied and is not financial advice.
- If inputs are remembered, say they are stored in this browser only.

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="mortgage-calculator">

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