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 APKKey FeaturesAI-Powered LearningAI 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 practiceAI Stories - Generate reading stories by theme and level with tappable word translation and comprehension quizzesDaily Challenge - Word of the day, phrase of the day, and mini quizSmart Learning SystemSM-2 Spaced Repetition - Scientifically-proven algorithm for optimal vocabulary retentionCEFR Level Assessment - A1 to C2 level placement with personalized contentLearning Path - Visual node-based curriculum with completion trackingPronunciation Guide - IPA phonemes with audio playbackTTS & STT - Text-to-speech and speech-to-text for all 20 languages20 Target Learning LanguagesSpanish · French · Japanese · Chinese · German · Korean · Italian · Portuguese · Arabic (RTL) · Hindi · Russian · Dutch · Turkish · Swedish · Polish · Greek · Vietnamese · Thai · Indonesian · UkrainianNote: These are the languages learners can study. The app interface itself is in English.Gamification30 Levels with XP progression25 Badges - unlockable achievementsStreak System - daily practice tracking with fire emojiHearts System - limited attempts that refresh dailyXP Chart - weekly progress visualizationCelebration Animations - confetti overlay on achievementsFull MonetizationRevenueCat - 3 subscription tiers (Monthly $4.99, Yearly $29.99, Lifetime $49.99)Google AdMob - Banner ads on main tabs + interstitial ads after sessionsPremium Gate - Ads hidden for premium usersFree Tier Limits - Configurable via Firebase Remote Config (no rebuild needed)AuthenticationEmail/Password registration and login Google Sign-In (Android & iOS) Apple Sign-In (iOS only) Forgot password with email reset User-friendly error messagesUser ExperienceOnboarding Flow - 4-slide intro, native language picker, target language selection, CEFR assessmentDark Mode - Warm dark theme (not cold black)RTL Support - Full Arabic right-to-left layoutCustom Transitions - Fade, slide-up, and scale animationsOffline SRS - Review vocabulary without internetPush Notifications - FCM + local streak reminders️ Tech StackFramework Flutter (Android + iOS)State Management Riverpod 2.xNavigation GoRouterBackend Firebase (Auth, Firestore, Remote Config, FCM)AI OpenAI GPT-4o + Google Gemini 2.5Models Freezed + json_serializableMonetization RevenueCat + Google AdMobFont Nunito (Google Fonts)What You GetFull 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 supportQuick SetupCreate Firebase project, add google-services.json and GoogleService-Info.plistEnable Authentication (Email, Google, Apple) Add OpenAI and Gemini API keys to Firebase Remote Config Run flutter pub get and flutter runDetailed setup instructions included in the documentation.RequirementsFlutter 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)ScreenshotsBrowse 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.DocumentationComprehensive 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.