How I built 1,200+ calculator pages in Astro without writing 1,200 templates

I run Hacé Cuentas, a free collection of 4,100+ Spanish-language calculators. What started as 10 hand-built pages turned into thousands of routes — and the codebase is actually smaller than when I had 50.

Here's how Astro's content collections + dynamic routes made it possible.

The problem

Every calculator needs:

Inputs (each with labels, validation, hints)