I added real-time online multiplayer to my Connect 4 browser game using Firebase

Hey everyone! 👋 I just shipped a big update to my Connect 4 game on 7x.games — online multiplayer is now live! What's new: 🌐 Online Multiplayer — play Connect 4 with anyone in the world in real-time 🔒 Private Rooms — create a room and share a unique invite link with a friend ⚡ Quick Match — get auto-paired with a random opponent 📤 Social Sharing — share invite links via WhatsApp, Telegram, Twitter/X, Facebook, or native share 🔗 URL Invites — friends click a ?room=XXXXXX link and they're straight into the game 📡 Real-time Sync — moves sync instantly between both players via Firebase Realtime Database 📱 Works on all devices — mobile, tablet, desktop — no app download needed What was already there: 🤖 3 AI difficulty levels (Easy = random, Medium = minimax depth 4, Hard = minimax depth 7 with alpha-beta pruning) 👥 Local Pass & Play mode 🎨 4 board themes (Classic, Obsidian, Forest, Crimson) 🔊 Sound effects & disc drop animations ↩️ Undo support (local only) Tech stack: Next.js (React, App R