My journey of making apps for myself started with Dual N-Back. I became interested in the exercise as a way to challenge working memory, tried an existing app, and hit a paywall right as I was building a twenty-day streak.
Around the same time, I tried Codex for the first time and thought: why not make this myself? So I did. It was shockingly easy to get the first version working, and it has since evolved into an iPhone and Mac app I use almost every day.
How it works
Each trial highlights a square and plays a spoken letter. I compare both with what appeared a few turns earlier, then mark visual or auditory matches. The app tracks accuracy, adjusts the difficulty, and shows how my performance changes over time.
A couple of favorite details
- Three natural-sounding voice options are bundled with the app, so training audio works offline with no API key or network delay.
- Statistics stay local. I can merge them between my iPhone and Mac with Universal Clipboard—no server, account, or paid Apple Developer membership required.
- The same core training engine powers the native SwiftUI experience on both platforms.
What began as a quick experiment became the first app I built purely to solve my own problem. That small success opened the door to making many more.