Built a free interactive mortgage calculator — drag sliders, see your numbers instantly. No ads, no paywalls

I built (vibe coded) Hearth because I wanted to understand my mortgage better without spreadsheets or sketchy online calculators.

It's a mortgage calculator that actually makes sense. Just drag sliders:
• Home price
• Down payment
• Interest
• Term
• Extra payments

See your full payment breakdown (principal vs interest), your amortization schedule, equity curve, and payoff date—all updating live as you move the sliders.

What makes it different:
• Free. Forever. No ads, no paywalls, no subscriptions.
• You own your data (it's all client-side if you want)
• Run scenarios — compare different down payments, interest, extra payment strategies side-by-side
• See exactly how much interest you save by paying extra
• Works on mobile (sliders responsive, charts clean)

Built this for myself and friends. Figure someone here might find it useful too.

Bookmark it if you find it useful—feedback always welcome.