Writing by Perttu Lähteenlahti

A collection of 27 blog posts I've written over the years. My writing spans topics like cognitive science, software development, and design — with the occasional detour into the unrelated. I revisit and revise older posts regularly, and I welcome any feedback that can help improve my writing, and more importantly, my thinking. I hope you find something interesting here.

App.js 2025 Recap

A personal recap of App.js 2025: speaking about in-app purchases, highlights from Krakow, favorite talks, and why this conference remains one of my top picks.

How to add subscriptions to a Bolt-generated Expo app

•RevenueCat

Want to add in-app subscriptions to your Bolt app? This guide shows how to build a working paywall UI using prompts only, then integrate RevenueCat to handle real purchases and entitlements on Android using EAS Build.

Vibe Coding is Prototyping For The Masses

How vibe coding shifts software development, why it’s closer to prototyping, and how domain-embodied development will change who builds the next generation of software.

Making Money with Your React Native App

Comprehensive look at in-app purchases and how to add them to your React Native app. Covers different types of in-app purchases, how to set them up in your app, and the psychology of good in-app purchase experiences. Technology used: React Native, RevenueCat, App Store Connect.

React Native WebRTC

Full article version of the talk I gave at RTC.ON Conference 2024 about getting started with WebRTC in React Native

The Novel vs. The Screenplay: Se7en

How Andrew Kevin Walker’s script went through multiple rewrites before becoming the neo-noir classic we know today. Despite its flaws, the novelization of Se7en holds personal significance for me, showing how a good story can transcend its medium.

How to Get The Old Slack UI Back

How to switch back to the old Slack desktop UI on Mac and say goodbye (at least temporarily) to the current UX catastrophe.

20 Things About 2020

20 things about 2020 from my perspective. I think there are easier ways to brag about your accomplishments than trying to mask them under an annual review.

Crosstalk in Stereoscopic Displays - Why 3D Movies Look Weird

Remember 3D TVs? Remember how the TV manufacturers tried to ship the idea of wearing goggles at home while watching TV, so you could experience that Avatar-style novelty from the comfort of your own couch? Although the idea 3D television is pretty much dead now, and everyone is more focused on the possibilities of AR and VR, I would not call 3D a dead technology yet. After all, cinemas are still pushing 3D movies and if we eventually crack the method for building glassless 3D televisions we could maybe even see the second coming of 3D at home. 3D has just been forgotten, a faith it has endured once before as well.

What I Read in 2018

A summary of the books I read in 2018, covering various genres and highlights.

Designing a Winning Hackathon Concept

Between the years 2015 and 2018 I participated in over 70 hackathons. I won 40 of them, most wins being towards the end. Sometimes winning was mostly accidental, but majority of the time it was due to a strategy me and our team followed. This article is abot trying to write down the strategy that worked.