Memory Match Game

# Memory Match Game PRD

## Overview
Build a card-matching memory game with multiple grid sizes, card themes, smooth flip animations, scoring, and a two-player mode.

## Requirements
- Grid of face-down cards that can be flipped
- Flip two cards at a time to attempt a match
- Match detection: keep matched pairs face up
- Flip cards back after a short delay if no match
- Multiple grid sizes: 4x3, 4x4, 6x6
- Card themes: emojis, animals, flags, numbers
- Move counter tracking total flips
- Timer tracking elapsed game time
- Star rating based on number of moves (fewer moves = more stars)
- Best scores per grid size persisted to localStorage
- Smooth card flip animation using CSS 3D transforms
- Game complete celebration effect
- Restart button to shuffle and replay
- Two-player mode with alternating turns and score tracking
- Lock board during flip animation to prevent extra clicks
- Shuffle cards randomly on each new game

## Tech Stack
- JavaScript or any frontend framework
- CSS for flip animations and layout
- No game libraries

## Scoring Criteria
- **Functional (40%)**: Card flipping works, matching logic correct, game completion detected
- **Quality (20%)**: Smooth animations, no flickering, proper board locking during flips
- **Fidelity (25%)**: All grid sizes, themes, two-player mode, and scoring features present
- **Speed (15%)**: Time bonus