I wanted to build a desktop breathing coach that makes it easy to relax and focus. Just choose a breathing technique, such as 5–5 cardiac coherence, Navy SEAL box breathing or the 4–7–8 method, close your eyes and follow the guided exercise. The protocols and the physiology come from a medical manual by Dr. Claudio G. Gallo (“I superpoteri del respiro”, 2026); the rest, as architecture, animation, audio synthesis, packaging, is what I built. It is deliberately local-first: no backend, no account, no telemetry, history stays on the device.

Then came the decision that shaped the whole project: build it native, twice, SwiftUI on macOS and TypeScript with Electron on Windows instead of one cross-platform codebase.

Native twice instead of cross-platform once

A single codebase would have shipped faster. But each platform got an implementation the way that platform expects: SwiftUI with a menu-bar companion and power-management APIs on macOS; a web-tech renderer with a custom frameless titlebar on Windows. The session engine — the state machine driving inhale / hold / exhale — exists twice, in Swift and in TypeScript, kept deliberately identical.

The clinical content exists exactly once: a structured JSON catalog is the single source of truth for protocols, mechanisms and contraindications, mirrored into both apps, so medical content can be reviewed without touching application code on either side.

{
  "id": "box-breathing",
  "name": "Navy SEAL box breathing",
  "phases": [
    { "label": "inhale", "seconds": 4 },
    { "label": "hold", "seconds": 4 },
    { "label": "exhale", "seconds": 4 },
    { "label": "hold", "seconds": 4 }
  ],
  "tags": ["#focus", "#stress"]
}

No 3D engine, no audio files

The animated torso, the part that shows where the breath should go, is a mathematical model drawn with 2D canvas primitives: elliptical rib rings, a parabolic diaphragm dome, hand-rolled yaw/pitch/perspective projection. No WebGL, no Three.js, no model downloads, no GPU requirement. The rib expansion follows real mechanics (+22% lateral bucket-handle, +30% sagittal pump-handle) and the diaphragm actively descends on inhale; physiology drives the animation.

Sound follows the same rule. Every soundscape, Tibetan singing bowls, Zen bells, solfeggio tones, ocean noise, is synthesized at runtime from oscillators, gain envelopes and biquad filters. No audio assets shipped, so installers stay small, tempo and pitch are programmable per breathing phase.

Small details that make a difference

• The Electron app is secure by default, with Node integration disabled, context isolation enabled, a sandboxed preload script and only six IPC channels exposed for window controls.
• A single VERSION file keeps all manifests in sync through a simple bump script, making builds consistent and reproducible from a clean checkout.
• The macOS app supports both Intel and Apple Silicon, while Windows installers are built directly from macOS, including ARM64 versions.