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Auri

A diet-adherence tracker for iOS that replaces charts and numbers with a living 3D orb. Log meals, tag them on-track or off-track, and watch your orb respond — more sparks, richer colors, faster orbits as adherence improves.

What It Does

Most diet apps lose users because logging feels like homework and feedback is abstract. Auri replaces spreadsheets and progress bars with a single interactive object: a luminous orb of orbiting sparks that embodies your adherence on a 0–100% continuum.

The underlying system is evidence-based — rolling adherence percentages calculated from meal logs — but the interface replaces judgmental numbers with something you actually want to look at and interact with. Low adherence isn't a punishment; it's a calm, resting state. High adherence is unmistakably vibrant.

The orb is a genuine fidget toy. Flick to spin the sparks. Tap to scatter them. Pinch to resize. Long-press to attract sparks to your finger. Two-finger twist to tilt the orbital plane. Shake your phone for chaos mode. Every gesture produces adherence-tuned haptic feedback — crisp and celebratory when you're doing well, soft and ethereal when you're not.

Tech Stack

  • Swift 6 / iOS 18 minimum deployment target
  • RealityKit — procedural 3D scene with hand-written mesh generation, quaternion-tilted orbital mechanics, object-pooled particle systems, and frame-synced animation via CADisplayLink at up to 120 Hz (ProMotion)
  • SwiftUI — 4-screen app with custom glass-morphism design system, environment-based service injection
  • SwiftData — local persistence for meals and user settings, no backend
  • Core Haptics — 8 distinct haptic patterns parameterized by adherence state
  • Core Motion — gyroscope-based shake detection for chaos mode
  • Swift Testing — modern test framework (@Suite, @Test, #expect)

Architecture

SwiftUI Views → Domain Services → SwiftData Models
       ↕
  RealityKit 3D (AuriScene)

Views — CoreView (home with 3D orb), LogMealView, DataView, OnboardingView. Components use a shared glass-morphism design system.

Services — MealService (CRUD + local JPEG photo storage), AdherenceEngine (calculates today/7-day/30-day rolling adherence with a non-linear reward curve), UserPreferencesService. All @Observable, injected via custom EnvironmentValues.

3D System — the most complex module (~2,800 lines). AuriScene orchestrates the RealityKit scene. Spark entities orbit on individually quaternion-tilted planes with spring-damped position physics. StateInterpolator maps adherence to visual parameters using piecewise interpolation. Supporting systems handle spin physics, multi-frequency breathing pulses, ambient particle motes (object-pooled), tier transition effects (procedural torus mesh), thermal throttling, and full Reduce Motion accessibility.

Notable Implementation Details

  • Delta-based spin physics — produces per-frame deltas instead of absolute angles to prevent jitter from wrapping discontinuities when multiplied by per-spark speed multipliers
  • Round-robin material batching — distributes GPU material updates across ~6 frames to prevent frame spikes at opacity quantization boundaries
  • Procedural torus mesh — hand-computed positions, normals, UVs, and triangle indices via MeshDescriptor for tier-upgrade ring effects
  • Thermal-adaptive rendering — monitors ProcessInfo.thermalState and independently throttles bloom, particle count, animation complexity, and frame rate
  • Non-linear reward curve — 1 - pow(1-x, 2.5) makes early progress feel disproportionately rewarding while keeping 80–100% visually distinct

Getting Started

Requires Xcode 16+ and iOS 18.0 SDK.

# Clone and open
git clone <repo-url>
open Auri.xcodeproj

# Build for simulator
xcodebuild -project Auri.xcodeproj -scheme Auri \
  -sdk iphonesimulator \
  -destination 'platform=iOS Simulator,name=iPhone 16 Pro' build

# Run tests
xcodebuild -project Auri.xcodeproj -scheme Auri \
  -sdk iphonesimulator \
  -destination 'platform=iOS Simulator,name=iPhone 16 Pro' test

No external dependencies. No backend. No API keys.

Status

MVP in active development. Core 3D visualization, meal logging, adherence calculation, onboarding flow, and data view are all functional. Not yet submitted to the App Store.

License

MIT