Obsidian Chess | 3D HTML5 Multiplayer Game

Version 1.0 | Three.js r128 | AI Minimax with Alpha-Beta Pruning | Online PVP via Firebase

Game Modes

• VS AI – Three difficulty tiers (Easy / Medium / Hard)
• Two Players – Local play on one device
• Online PVP – Real-time multiplayer via Firebase Realtime Database. Quick Match auto-pairs players. Create or join private rooms using a 6-character code. In-game chat included.

AI Difficulty

• Easy – Shallow depth + randomized move ordering
• Medium – Balanced depth + full heuristic evaluation
• Hard – Maximum depth + tight alpha-beta cutoffs

Board Themes (8 + Custom Builder)

• Obsidian (free) / Classic (free) / Forest / Ocean / Royal / Ember / Arctic / Night
• Custom Theme Builder – Live preview, 5 color pickers (light squares, dark squares, background, panels, accent)
• Themes above Classic are unlocked with in-game coins earned through gameplay or reward ads

Coin & Economy System

• Earn coins by winning games vs AI or Online PVP – stored locally, no account needed
• Daily bonus of 15 coins awarded automatically on first session each day
• Win reward: 50 coins per victory. Watch a voluntary reward ad for +10 coins instantly.
• Hint Button – Costs 5 coins. Highlights the best available move on the 3D board for 2.2 seconds. Available in VS AI mode only.
• Spend coins to unlock premium board themes from the in-lobby or in-game theme store

Online PVP Features

• Quick Match – Atomic Firebase transaction matchmaking. Works even when both players connect at the exact same moment.
• Create Room – Generate a 6-character code and share with a friend
• Join Room – Enter a friend’s code to connect directly
• In-Game Chat – Real-time messaging panel during the match
• Turn Timer – 10-second countdown per turn. Auto-moves if time runs out. Only the active player’s client runs the timer to prevent desync.
• Disconnect Detection – Opponent going offline is detected via Firebase presence and handled gracefully
• Display Names – Random or custom player names shown in the HUD during the match
• Coin Rewards – Online wins award 50 coins on the winner’s device only

Chess Rules

• Full legal-move validation: pins, checks, discovered attacks
• Castling (kingside & queenside) with correct invalidation rules
• En passant capture
• Pawn promotion – interactive modal (Queen / Rook / Bishop / Knight)
• Check, Checkmate, and Stalemate detection
• 50-Move Rule and Threefold Repetition draws
• Insufficient Material detection (K vs K, K+N vs K, K+B vs K)
• Algebraic notation move log (e.g. Nf3, O-O, exd5+) displayed in the sidebar
• Captured pieces displayed per side in the sidebar
• Undo – steps back one half-move (or two in AI mode, to restore the player’s turn)

Controls

• Click / Tap – Select piece, then click highlighted square to move
• Drag – Orbit the 3D board freely
• Scroll / Pinch – Zoom in and out
• Escape – Pause / Resume (also closes Settings overlay)
• Hint Button – Flash best move on board (costs 5 coins, VS AI only)

Overlay & UI System

• Pause, Resign Confirm, Pawn Promotion, Game Over, Unlock Theme, Pre-game Countdown
• Zero native browser popups – all custom HTML overlays throughout
• Animated lobby screen transitions with page-enter / page-exit effects
• Light Mode toggle – switches to a warm parchment lobby aesthetic
• Asset pre-load screen with live progress bar and status messages

Advertisement System

• Pre-game ad – Shown automatically before every match starts (VS AI, Local PVP, and Online PVP). Player watches 5 seconds and earns +2 coins, then a 3-second countdown begins the game.
• Voluntary reward ad – Triggered manually from the lobby coin badge or Earn More button. Player watches 5 seconds and earns +10 coins.
• Both ad overlays use matching warm lobby chrome – fully consistent visual design
• Placeholder sized to Google AdSense 300×250 Medium Rectangle standard – ready for integration

Tech Stack

• Three.js r128 (3D rendering, WebGL, PCF soft shadow maps)
• OrbitControls for drag-to-orbit and pinch-to-zoom
• Web Audio API – all sounds synthesized in-browser, no audio files required
• CSS Custom Properties (theme tokens for live board color switching)
• ES2015+ JavaScript (IIFE-scoped modules, no global leaks)
• Firebase Realtime Database (loaded on demand for Online PVP only, not on page load)
• requestAnimationFrame render loop with damped OrbitControls
• LocalStorage for coins, unlocked themes, player name, and preferences

Requirements

• Chrome / Firefox / Safari / Edge / Opera (Latest)
• Internet connection required for Online PVP and Firebase
• No build step – open index.html directly or deploy to any static host
• WebGL support required for 3D board rendering