TrackCold

The brief

Cold therapy is booming — cold plunges, ice baths, Wim Hof breathing, contrast therapy. But tracking sessions is stuck in spreadsheets and generic fitness apps that don't understand multi-round protocols, temperature logging, or the cold-to-sauna contrast flow.

Design and build a native iOS app purpose-built for cold therapy. Multi-round timers for contrast therapy, automatic temperature tracking, achievement system to build consistency, and iCloud sync across devices. Ship a polished 1.0 for the cold plunge community.

Workout setup

Three cold types — plunge, shower, natural water — and eight warm recovery types including sauna, steam room, hot tub, and infrared. Timer or stopwatch mode, independently configurable for cold and warm phases. One to five rounds with cold-first or warm-first ordering and configurable transition time between phases.

Quick-start presets at the top let regulars launch their favorite session in one tap. A visual phase flow at the bottom shows exactly what you're about to do before you step into the cold.

Active session

The active workout screen changes its entire color temperature based on the current phase — cyan for cold, orange for warm. A large circular timer dominates the screen with phase dots below showing your progress through the session.

Pause, skip, or end at any time. The app survives backgrounding with full state persistence — if you lock your phone mid-plunge, it reconciles elapsed time from saved timestamps when you return. Haptic feedback pulses on countdown ticks, phase transitions, and session completion. Stale sessions older than 24 hours are cleaned up automatically.

Session summary

Every session ends with a clear breakdown — total time, cold time, rounds completed, and a phase-by-phase timeline with durations and temperature readings. Add notes, save the configuration as a preset for next time, or jump straight into another session.

Newly unlocked achievements appear inline, giving immediate recognition for hitting milestones.

History & detail

Searchable session history with cold type filtering. Each card shows the date, cold type emoji, total duration, and cold time at a glance. Tap into any session for the full phase-by-phase breakdown with temperature data and notes.

Swipe to delete with confirmation. All data syncs across devices via iCloud — start a session on one iPhone, review it on another.

Achievements

18 achievements across five categories — milestones (first plunge to 365 sessions), streaks (3-day to 90-day), records (5-minute and 10-minute cold endurance), and special unlocks for early-bird plungers, night owls, weekend warriors, and contrast therapy completionists.

Each unlock triggers a confetti celebration modal with the achievement emoji, name, and description. Multiple unlocks queue sequentially so nothing gets lost. The gallery view lets you browse all achievements with category filtering and a progress ring showing overall completion.

Goals & progress

Weekly and monthly goals with three metrics — session count, total cold time, and streak days. Progress rings fill up as you complete sessions, with color-coded feedback: warning below 50%, primary up to 99%, and success green at completion.

Days remaining and motivational messages keep you on track without negativity — progress is always framed positively.

Contrast therapy

The killer feature that no other cold therapy app does well. Alternate between cold plunge and sauna, steam room, or hot tub across multiple rounds with smooth transitions. Phase flow visualization shows the entire sequence before you start — cold-first ends on cold (2n-1 phases), warm-first includes a final recovery (2n phases).

Each phase tracks independently with its own timer mode, duration, and temperature. The UI shifts from cyan to orange as you transition between cold and warm, making the current state impossible to miss even when your hands are freezing.

Technical details

100% native SwiftUI with zero third-party dependencies. MVVM architecture with the Observation framework for fine-grained reactivity. SwiftData with CloudKit for automatic cross-device sync. Strict concurrency enforced at compile time with zero warnings.

Complex workout configs stored as JSON blobs in SwiftData for schema flexibility. Static JSON coders and reused haptic generators for performance. Full session state persistence — survives app kills with timestamp-based time reconciliation. 22+ unit tests covering core logic, streak calculation, and goal progress.

Results

Built from concept to App Store submission with product strategy, UX/UI design, and full SwiftUI development handled in-house. 38 Swift files, 4,500+ lines of code, 18 achievements, 8 recovery types, and contrast therapy support that competitors don't offer.

The same SUUR approach: understand the niche, build only what matters, ship with polish.