Propina

Propina is a tiny tip calculator for trips between the US and Mexico. You type in the bill, pick a tip percentage, and say how many people are splitting it — and every answer shows up in both dollars and pesos, so nobody at the table has to do the conversion in their head.

It is one single web page, with nothing to install and nothing sent anywhere. The exchange rate is a box you fill in yourself (it starts at 18.00 pesos per dollar), because the author deliberately left out any live rate feed: one less thing that can break in six months. Tip buttons cover 10%, 15% and 20%, plus a custom box, and the totals update as you type.

Vibe-coded evidence, in the author's own words on DEV (15 October 2026): "I built a USD/MXN tip calculator with Cursor for the Build a Mini App challenge during Hacktoberfest and MLH Global Hack Week. One prompt, one commit, no corrections, and the site was live on GitHub Pages eight minutes after I first asked for a prompt." The repository page backs it up: the first commit is co-authored by the author and cursoragent, and a second commit fixed two small review findings. GitHub stars: 2, checked on 29 October 2026.

Honest limits: there is no live exchange rate, no saved history, no rounding options and only this one currency pair — if you need euros, the author says to fork it and change two strings. It is a small, finished tool, not a growing app, and the last push was 15 October 2026.