I Built and Shipped a $39 macOS App in One Day (Here's How)

Yesterday I had an idea. Today it's on Gumroad making money.
Here's exactly how I shipped HiyokoBar — a menu bar HUD for engineers — in a single day.

The Idea
I was constantly alt-tabbing to check Docker status, GitHub PRs, server health.
I wanted something that pushes information to me, not something I have to pull from.
Raycast is great but it's Pull-type. You invoke it when you need it.
I wanted a HUD that's always there — like a cockpit instrument panel for my Mac.

The Unfair Advantage: Code Reuse
I didn't start from zero. I have a portfolio of macOS utility apps built with Rust + Tauri 2.0, and I ruthlessly reused everything I could:
ComponentSourceMenu bar skeletonHiyokoHelper (internal app)Keychain storageHiyokoKitGumroad license authHiyokoShotParallel executionHiyokoAutoSyncGemini AI integrationHiyokoLogcat
The menu bar app architecture — tray icon, click to show/hide, window positioning — was already battle-tested. I just dropped in new features.
This is why building a product suite matters more than one-off apps.

Timeline
Morning

Copied HiyokoHelper as the base
Replaced window positioning with tauri-plugin-positioner
Got the HUD dropping down from the menu bar icon

Midday

Built the shell script execution engine in Rust
Card UI in React with Framer Motion animations
Polling with random jitter to avoid CPU spikes

Afternoon

Gemini AI error analysis (ported from HiyokoLogcat)
GUI settings editor — no JSON required
Drag & drop card reordering
Real-time countdown timers

Evening

Gumroad license auth (ported from HiyokoShot)
macOS Keychain for API key storage
OWASP security audit (caught a critical A02 bug — API keys were stored in plain JSON instead of Keychain)
i18n (Japanese / English)
Gumroad listing, README, pricing

Total: ~8 hours

The Security Audit Saved Me
Before shipping, I ran through OWASP Top 10 for native apps.
Found a critical bug: despite the design doc saying "store in Keychain," the actual implementation was saving API keys in plain JSON.
A quick audit before shipping caught what code review missed.
Always check OWASP before you ship. Even for "simple" apps.

Pricing: $39 One-Time
I originally planned $29. Looked at what I built and charged $39.
The target is senior engineers. They don't blink at $39 for a tool they'll use every day. Underpricing signals low quality to this audience.

What's Next

Product Hunt launch this week
v3.0 ideas: community recipe store, macOS notifications, multi-AI support

Try It

HiyokoBar: https://hiyokoko.gumroad.com/l/hiyokobar

🇯🇵 日本語版: https://hiyokoko.gumroad.com/l/hiyokobar_jp

🐤 Launched on Product Hunt today — would love your support!
https://www.producthunt.com/products/hiyokobar

X: @hiyoyoko