Major Game Update: Realistic Planets, Black Hole Catcher, Infinite Mode, Login & Leaderboard

## Overview
This is a major update proposal for "Celestial Catcher v2" to transform the game's visuals, mechanics, and player experience while retaining the core gameplay.

### Features & Enhancements

1. **Replace Colored Balls with Realistic Planets**
- Replace color balls with visually accurate representations of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
- Use high-quality images or custom canvas rendering for each planet, ensuring unique textures and realistic appearances.
- Update all UI and game logic to reference planets by name.

2. **Black Hole Catcher**
- Redesign the catcher to look like a realistic black hole, featuring event horizon, accretion disk, and gravitational lensing effects.
- Add animated swirling and visual effects for immersion.

3. **Infinite Level System**
- Remove the current sector/level progression.
- Implement endless gameplay: player scores can increase infinitely.
- Dynamically increase difficulty over time via spawn rates, object speeds, and new hazards.

4. **Challenging & Interesting Gameplay**
- Add new obstacles: asteroid belts, rogue comets, space debris, unpredictable planet movements, variable gravity.
- Introduce more power-ups: temporary shields, slow-motion, enhanced score multipliers.
- Make game progressively harder and less predictable as score rises.

5. **Animated Home Page Theme**
- Create a visually dynamic home screen with animated stars, planets, and black holes.
- Use smooth transitions, parallax effects, and engaging background music.
- Ensure the home page is highly attractive and sets the tone for the game.

6. **Login Interface (Google Authentication)**
- Require players to log in with Google before playing.
- Integrate Google Sign-In API, and store user profile (name, avatar, Google ID).
- Ensure seamless authentication flow.

7. **Global Leaderboard**
- Add a leaderboard screen showing global player rankings, scores, and player info (name/avatar).
- Implement backend integration (e.g., Firebase, Supabase, or custom REST API) for storing and retrieving scores.
- Leaderboard updates on game over and at regular intervals.

8. **Preserve Gameplay Experience**
- Retain core "catch planets" gameplay and user flow.
- All enhancements should build upon and not disrupt the established mechanics.

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### Acceptance Criteria
- Realistic planet graphics are used throughout the game.
- Catcher is visually a black hole with animated effects.
- Gameplay is endless, with difficulty scaling over time.
- Home page features animated stars, planets, and black holes.
- Google login is required to play; player info is stored.
- Global leaderboard displays logged-in players' scores and ranking.
- All UI and logic changes are tested and do not negatively impact core gameplay.

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### Additional Notes
- If using external services/APIs, ensure privacy and data security.
- Consider mobile and desktop responsiveness for all new UI elements.

La proposition ne nomme aucun fichier, test ou point d’entrée ; commencez donc par cartographier les flux existants du gameplay, de l’écran d’accueil, de l’authentification et du stockage des scores. Considérez les critères d’acceptation listés comme la checklist d’achèvement, notamment des visuels réalistes de planètes et de trous noirs, une progression de la difficulté sans fin, la connexion avec Google, un classement mondial et des tests de régression.

Rédigé par le modèle d'indexation à partir du texte de l'issue.