Extend Existing Speech Practice App (Firebase Backend)Project Overview We have an existing Flutter mobile application designed to help children practise speech sounds at home while waiting for speech therapy support. The core functionality has already been developed using Flutter and Firebase. We are now extending the app with two additional learning activities that reuse the existing sound library and database structure. Existing System • Flutter mobile app • Firebase Firestore backend • Sound library (~500 sound records) • Audio playback and recording • Practice session engine with progression tracking • Reward stickers and avatars • Firebase Storage for recordings and images New Features Required Activity Selection Screen Add a screen allowing users to choose: Practice (existing feature) Listening Activity Find the Sound Resources Listening Activity • App plays an audio word • Two image options appear • Child selects the correct image Find the Sound Activity Prompt example: Which word starts with /b/? • Three image options appear • One correct answer • Two distractors Activity Logic Activities must: • Query sounds where image_ready = true • Query sounds where activity_enabled = true • Select target words from the child's current_group • Use the full illustrated pool for that group • Generate 4 questions per session • Randomise answer order Distractor Rules Listening Activity 1 target 1 distractor from a different sound group Find the Sound 1 target 2 distractors from two different sound groups Additional Rules • Do not repeat the same target within a session • Avoid repeating distractors within a session Backend Logging Each activity attempt must store: activity_type child_id sound_id word selected_answer correct_answer is_correct response_time_ms Resources Tab Simple screen listing external helpful links that open in the device browser. Milestone Structure Milestone 1 Activity selection screen Listening Activity Randomised word logic Firestore attempt logging Milestone 2 Find the Sound Activity Resources tab Final testing and integration Requirements Flutter development experience Firebase Firestore experience Clean scalable code structure Assets Provided Sound library spreadsheet Audio recordings Illustrated word images Goal Extend the existing application while keeping the architecture scalable so additional sounds and activities can be added later without rebuilding the system.