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What I learned building ProofPack

ProofPack was my first complete app. Here is what I got right, what I got badly wrong, and what I would do differently if I started today.


What ProofPack was

  • My first real mobile app — not a tutorial project, not a prototype.
  • An actual app that I built, submitted, and published on the Play Store.
  • It took longer than I expected and broke more than I wanted.
  • It taught things no course could — because real things break in ways tutorials do not.

The biggest thing I got wrong: scope

  • My original idea for ProofPack was enormous — I wanted it to do ten things.
  • I ended up building the version that did one thing well.
  • Even that took three times longer than I expected.
  • The ten-thing version would have taken forever and probably never shipped.
  • Start smaller than feels right. Then start smaller than that.

The second thing I got wrong: how I used AI

  • For the first few weeks I treated Codex like a magic wand.
  • I would paste enormous blocks of code and ask it to "fix everything."
  • The results were unpredictable — sometimes helpful, often worse than before.
  • The fix was simple: ask for one change at a time, every single time.
  • That one rule changed every session that came after.

What I got right: GitHub from day one

  • I committed after every working change from the very beginning.
  • This saved me at least four times during the build.
  • Once when Codex rewrote half my navigation by accident.
  • Once when an updated dependency broke everything.
  • Once when I deleted a file I thought I no longer needed.
  • GitHub was the difference between losing a week of work and losing an afternoon.

The habit I am most glad I kept: documenting as I went

  • Every prompt that worked — written down.
  • Every error I hit — recorded.
  • Every fix that solved it — noted.
  • That documentation became the foundation for what I now share on NonDev Apps.
  • If you are not documenting your working prompts, you are rebuilding from scratch every session.

What I would do differently if I started today

  • Start with a much smaller idea than feels right.
  • Commit to GitHub every thirty minutes instead of once a day.
  • Write prompts as if explaining the problem to a careful friend — not shouting at a magic box.
What I learned building ProofPack — NonDev Apps