Need an Embeddable Website Widget Built (Calculator or Product Selector)

We run a website and want to add an interactive widget that visitors can use directly on a page — most likely a price calculator or a short form that helps someone pick the right product after answering a few questions. It needs to work as a self-contained block we can paste into several different pages, and possibly hand off to a partner site, without touching the rest of the layout or fighting with styles already in use there.

We are not tied to a specific framework. What matters more is that it loads fast, does not conflict with other scripts on those pages, and looks reasonable inside our current theme without heavy custom styling. The logic itself is fairly simple: a few input fields, a calculation or filtering rule, and a result block once the visitor finishes entering data. We would like those values to be easy to adjust later without opening the code, ideally through a small settings file.

If you have built something similar before, please share a working example rather than a screenshot — we want to see how it behaves on a real page and on a phone.

Rough scope:
— input form with basic validation
— calculation or matching logic behind it
— responsive result display
— a lightweight snippet for embedding on any page
— short instructions for installing it on a new page