Sarafis Abacus — a teacher-ready number-sense app for Grades 1–2. Children learn make-10, compose/decompose, and place-value with a dual-color abacus (5/10) and guided 5–7′ lessons. MVP is English-only (architecture i18n-ready). Engagement: Fixed-price with milestones PAID test task. Start ASAP. What you’ll build (MVP) 1. Abacus Engine (“rekenrek”) • 8–10 rails, dual-color 5/10, smooth gestures/animations (60 fps). • Automatic exchanges: 10 ones→1 ten, 10 tens→1 hundred, etc., with visual/audio cues. • Place-value indicators (Ones/Tens/Hundreds/Thousands). 2. Three modes • Guided micro-lessons (5–7′). • Practice/Challenges (timed rounds, streaks, badges). • Sandbox for teachers incl. projector “curtain” to hide/reveal. 3. Four initial lesson units • Counting & Number Sense; Compose/Decompose; Make-10 (over the ten); Add/Subtract 2-digit (with/without regrouping). 4. Teacher basics • Quick progress overview (per skill), export simple PDF handouts. 5. App qualities • Offline-first (usable with no signal; sync when online). • Accessibility: large targets; left/right-hand toggle; color-blind-safe patterns; haptics & audio cues. • No ads. Child-friendly flows. Tech stack (must-have) • React Native (Expo managed, TypeScript) • Animations/Gestures: react-native-reanimated, react-native-gesture-handler • Rendering: @shopify/react-native-skia (or equivalent) • State: lightweight (Zustand or Redux Toolkit) • Firebase (EU region): Auth (email Apple/Google), Firestore (offline persistence), Storage, Cloud Messaging (FCM), Analytics (GA4), Crashlytics, App Check • Build/Release: EAS Build/Submit (TestFlight / Google Play Internal) • Audio/TTS: expo-av / expo-speech (English) • Quality: Jest RN Testing Library; basic Detox E2E for one core flow Non-functional requirements • Targets: iOS 16, Android 10; phones first, tablets OK. • Performance: 60 fps interactions on mid-range devices; cold launch <3s. • Security: Firestore Security Rules (role-based), least-privilege IAM, App Check. • Privacy: data minimization, EU data residency, GDPR-aware; COPPA-friendly (no ads/tracking for kids). • Content: lessons/strings bundled locally (JSON) remote config flags. Deliverables & milestones (fixed price) M1 — Abacus Engine (Week 1–2): rails, gestures, one exchange (10 ones→1 ten). Acceptance: 60 fps demo Expo build. M2 — Lesson System & Make-10 (Week 3): lesson runner; full Make-10 unit; offline persistence. Acceptance: run offline; GA4 events; TestFlight/Play build. M3 — Compose/Decompose 2-digit Add/Sub (Week 4–5): units 10-round challenge; local progress syncs to Firestore. Acceptance: works offline→online. M4 — Teacher Basics & Sandbox Curtain (Week 6): curtain mode; reports lite (attempts, accuracy, time); PDF export. Acceptance: sample class report PDF; GA4 key events. M5 — QA & Beta (Week 7–8): accessibility pass; Crashlytics; FCM streak reminder; store-ready builds README, setup docs, test plan. Acceptance criteria (sample) • Functional: exchanges correct across O/T/H/Th; guided steps never dead-end. • Offline: all lessons run in airplane mode; sync on reconnect. • Analytics: GA4 events — session_start, lesson_start/complete, make10_success, exchange_event, error_count. • Performance: avg frame time ≤16.7ms; memory stable. • Security: Firestore Rules reviewed; App Check enabled; no secrets in repo. • Release: EAS pipelines; signed artifacts; crash-free sessions ≥99% in beta. How we’ll work • Tools: GitHub (private), Expo EAS, Notion/Trello, Slack. • Cadence: weekly demo (20–30 min); async daily update (3 bullets). • Code: PRs with reviews; small feature branches. Paid test task (8–12 hours) Mini abacus with 8 rails, dual-color 5/10, one exchange (10 ones→1 ten) simple Make-10 stepper. Save a local progress flag and sync to Firestore when online. Deliver Expo link short Loom repo. This task is paid. Your profile (must-have) • 2 shipped React Native (Expo) apps (links) and Firebase mobile experience (Firestore offline, Rules, FCM, GA4). • Strong animations/gestures; performance mindset. • Clear English communication; reliable & proactive. Proposal instructions (include) 1. Two app links your role. 2. Offline-first pattern you use with Firestore. 3. How you’d implement exchange logic at 60 fps. 4. Fixed-price per milestone total for 8–10 weeks; earliest start. 5. Confirmation you accept: IP assignment, NDA, GDPR-friendly handling, milestone-based payments.