Peter Bartfai

Guides

The parts that don't change.

Everything here comes from eleven years of building and selling software products, including one expensive failure. It's the part that doesn't change month to month: how to find out whether anyone will pay before you build, and how to plan a product clearly enough that AI can actually build it.

These used to be part of a course. They're not a course anymore. Every guide stands on its own, nothing is locked, and you don't have to start at the beginning.

3 guides2 seriesFree, nothing locked

Before you build: validation

2 guides

7 min read

What actually counts as validation

Sign-ups aren't proof and interest isn't proof. Here's the test I use now, and what it looked like when I applied it to my own product.

Before you prompt: planning

1 guide

The build notes

Every decision that costs real money or real time.

I'm building and selling my own products alongside client work. Every decision that costs real money or real time goes into an email: what I chose, what I passed on, what it cost, and what actually moved the numbers.

I don't send it on a fixed schedule. I send one when there's something worth sending.

Free · one click to leave · nothing else

Peter Bartfai designs and builds software products in Budapest — for clients during the week, and for himself after hours.

© 2026 Peter Bartfai · still doing it for clients every weekPrivacy