LinguaAI — Speak Any Language with AI

LinguaAI is a complete, production-ready AI language learning app built with Flutter. It combines the power of OpenAI GPT-4o and Google Gemini to deliver an immersive, personalized learning experience across 20 languages.

Whether you’re building a language learning startup or adding AI-powered education to your portfolio, LinguaAI gives you everything you need — ready to customize, rebrand, and publish.

Download Demo APK

Key Features

AI-Powered Learning

AI Conversation — 5 modes: Free Chat, Scenario, Guided Lesson, Role Play, Correction Mode (powered by OpenAI GPT-4o)
AI Vocabulary Cards — Generate flashcards with pronunciation, examples, and cultural notes (powered by Google Gemini)
AI Grammar Lessons — Auto-generated lessons with concept explanation, examples, and interactive practice
AI Stories — Generate reading stories by theme and level with tappable word translation and comprehension quizzes
Daily Challenge — Word of the day, phrase of the day, and mini quiz

Smart Learning System

SM-2 Spaced Repetition — Scientifically-proven algorithm for optimal vocabulary retention
CEFR Level Assessment — A1 to C2 level placement with personalized content
Learning Path — Visual node-based curriculum with completion tracking
Pronunciation Guide — IPA phonemes with audio playback
TTS & STT — Text-to-speech and speech-to-text for all 20 languages

20 Target Learning Languages

Spanish · French · Japanese · Chinese · German · Korean · Italian · Portuguese · Arabic (RTL) · Hindi · Russian · Dutch · Turkish · Swedish · Polish · Greek · Vietnamese · Thai · Indonesian · Ukrainian

Note: These are the languages learners can study. The app interface itself is in English.

Gamification

30 Levels with XP progression
25 Badges — unlockable achievements
Streak System — daily practice tracking with fire emoji
Hearts System — limited attempts that refresh daily
XP Chart — weekly progress visualization
Celebration Animations — confetti overlay on achievements

Full Monetization

RevenueCat — 3 subscription tiers (Monthly $4.99, Yearly $29.99, Lifetime $49.99)
Google AdMob — Banner ads on main tabs + interstitial ads after sessions
Premium Gate — Ads hidden for premium users
Free Tier Limits — Configurable via Firebase Remote Config (no rebuild needed)

Authentication

Email/Password registration and login
Google Sign-In (Android & iOS)
Apple Sign-In (iOS only)
Forgot password with email reset
User-friendly error messages

User Experience

Onboarding Flow — 4-slide intro, native language picker, target language selection, CEFR assessment
Dark Mode — Warm dark theme (not cold black)
RTL Support — Full Arabic right-to-left layout
Custom Transitions — Fade, slide-up, and scale animations
Offline SRS — Review vocabulary without internet
Push Notifications — FCM + local streak reminders

️ Tech Stack

Framework	Flutter (Android + iOS)
State Management	Riverpod 2.x
Navigation	GoRouter
Backend	Firebase (Auth, Firestore, Remote Config, FCM)
AI	OpenAI GPT-4o + Google Gemini 2.5
Models	Freezed + json_serializable
Monetization	RevenueCat + Google AdMob
Font	Nunito (Google Fonts)

What You Get

Full Flutter source code (Android + iOS)
15+ screens, 15+ providers, 15+ Freezed models
81 unit tests
Comprehensive HTML documentation (offline)
Quick start guide with step-by-step setup
Firestore security rules template
6 months of support

⚡ Quick Setup

Create Firebase project, add google-services.json and GoogleService-Info.plist
Enable Authentication (Email, Google, Apple)
Add OpenAI and Gemini API keys to Firebase Remote Config
Run flutter pub get and flutter run

Detailed setup instructions included in the documentation.

Requirements

Flutter SDK 3.29.2+ (Dart SDK 3.7.2+)
Firebase account (free tier works for development)
OpenAI API key (pay-as-you-go, ~$0.10-0.50/user/month)
Google Gemini API key (free tier available)
RevenueCat account (free for <$2.5k/month revenue)
AdMob account (optional)

Screenshots

Browse the item preview gallery above for full-resolution screenshots covering: onboarding flow, AI conversation (5 modes), vocabulary SRS, AI grammar lessons, AI stories with tappable translations, daily challenge, learning path, paywall, profile, and dark mode.

Documentation

Comprehensive offline HTML documentation is included with the source download. Open Documentation/index.html in any browser for the full guide, or QuickStart/quick-start.html for a 15-minute step-by-step setup.

The documentation covers:

Firebase project setup (Auth, Firestore, Remote Config, FCM)
Production-ready Firestore security rules
RevenueCat in-app purchase configuration
AdMob banner and interstitial ad setup
OpenAI and Gemini API key configuration with cost breakdown
Android release signing (keystore + key.properties)
iOS Apple Sign-In, APNs, and Info.plist permissions
12-point production checklist
Troubleshooting guide (build, Firebase, AI, monetization, runtime)

⚠️ Third-Party Service Costs (Not Included)

This item’s purchase price covers the source code only. The third-party services listed below are required to run the app and are NOT included in the item price. Buyers are responsible for any usage-based or subscription fees charged directly by the providers:

OpenAI API — pay-as-you-go. Estimated $0.10–0.50 per active user per month for typical usage. Pricing: openai.com/pricing
Google Gemini API — generous free tier; paid pricing applies above quota. Pricing: ai.google.dev/pricing
RevenueCat — free up to $2,500/month tracked revenue; percentage fee applies above that threshold. Pricing: revenuecat.com/pricing
Firebase — Spark (free) tier is sufficient for development and small user bases; Blaze (pay-as-you-go) applies once free quotas are exceeded. Pricing: firebase.google.com/pricing
Google AdMob — no cost to use; revenue share applies on impressions.
Apple Developer Program — $99/year (required for App Store publishing).
Google Play Developer — $25 one-time fee (required for Play Store publishing).

A detailed cost breakdown with per-request and per-user monthly estimates is provided in the included documentation.

Support

We provide dedicated support for all buyers:

Email: devsnack26@gmail.com
WhatsApp: +855 967 413 911

Response time: within 24 hours on business days.

Support includes:

Help with initial setup and configuration
Firebase and API key configuration assistance
Bug fixes related to the original source code
General questions about customization

Note: Support does not cover custom feature development, third-party service issues, or modified source code bugs.

Changelog

v1.0.0 — Initial Release

24 features across 6 development phases
20 target learning languages with RTL Arabic (app UI is English-only)
AI conversation, vocabulary, grammar, stories, daily challenge
SM-2 spaced repetition system
Gamification with 30 levels and 25 badges
RevenueCat subscriptions + AdMob ads
Email, Google, and Apple authentication
Dark mode + custom screen transitions
81 unit tests
Comprehensive offline documentation

LinguaAI | Flutter App | Education