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 Router)
Firebase Realtime Database for room management & move sync
Web Audio API for sound effects
No external game engine — pure React + CSS animations
How multiplayer works:
Player 1 creates a room → Firebase stores room state
Player 1 shares the invite link
Player 2 opens the link → auto-joins the room
Both clients listen to the same Firebase path via onValue
When a player clicks a column, the move is pushed to Firebase
Both clients process the move locally — board state stays in sync
The room creator always plays as Red (goes first), and the joining player is Yellow.

Would love any feedback! Try it out: Click here

📋 Changelog / Release Notes
Connect 4 — v2.0 | Online Multiplayer Update
Release Date: March 31, 2026

✨ New Features
Online Multiplayer — Real-time 2-player matches via Firebase
Private Rooms — Create a room and share an invite link
Quick Match — Auto-pair with a random waiting player
Social Sharing — Share invite links via WhatsApp, Telegram, Twitter/X, Facebook
URL Invites — ?room=XXXXXX parameter for instant join
Opponent Disconnect Detection — Shows "Opponent Left" screen with return to lobby
Leave Game — Clean disconnect that marks the room as abandoned
🔧 Improvements
Sidebar ad fixed from aspect-square to fixed h-[250px] for proper tablet sizing
SEO metadata updated for online multiplayer keywords
FAQ expanded from 5 to 9 questions covering online features
New "Online Multiplayer" section in page SEO content
Quick Rules updated with 🌐 Online entry
🛡️ Preserved
All existing local play modes (vs Computer + vs Friend)
3 AI difficulty levels (Easy, Medium, Hard)
4 board themes
Undo support (local only)
Sound effects and animations