⛓ BlockChain Coin Collector — M.Tech Seminar Demo

Real-time 2D coin collection game proving:

• Decentralized sync via GUN.js peer-to-peer
• Tamper-proof ledger via SHA-256 chained blocks

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Setup (3 steps)

1. Copy game files into your project

public/game.html   ← main game page
public/game.js     ← game logic + blockchain + GUN sync
public/game.css    ← professional dark UI

2. Add /game route to your server.js

Open your existing server.js and add ONE line inside your routes:

app.get('/game', (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'game.html'));
});

See server-patch.js for the exact placement.

3. Run

npm start
# Open → http://localhost:3000/game

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Seminar Demo Script

Step	Action	Shows
1	Open /game in two browser tabs	Two independent players
2	Start game, collect coins	Score updates in real-time in both tabs via GUN
3	Watch Blockchain Ledger panel	Every coin event creates a signed block
4	Click Verify Integrity	All blocks go green — SHA-256 chain valid
5	Click Simulate Tamper	Middle block score is altered (no hash update)
6	Click Verify Integrity again	Red warning, corrupted block highlighted

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Architecture

Browser A                    GUN Relay (your server.js)       Browser B
─────────                    ──────────────────────────       ─────────
Collect coin                         │                        Watching
  → SHA-256 hash new block           │                          ↓
  → gunScores.put(score)  ──────────►│◄────────────── gunScores.map().on()
  → gunEvents.put(block)             │                     score updates
  → Local blockchain[]               │                        live

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Blockchain Block Structure

{
  "index": 3,
  "timestamp": 1718000000000,
  "player": "player_AB12C",
  "event": "COIN_COLLECTED",
  "prevScore": 20,
  "newScore": 30,
  "posX": 284,
  "posY": 195,
  "previousHash": "a1b2c3d4e5f6...",
  "hash": "7g8h9i0j1k2l..."
}

Hash = SHA-256(index|timestamp|player|event|prevScore|newScore|posX|posY|previousHash)

Tampering any field → hash mismatch → TAMPERING DETECTED 🔴

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Viva Q&A Cheat Sheet

Q: How is this decentralized?
A: GUN syncs peer-to-peer without a central database. The relay server is just a message broker — any peer can relay.

Q: How does tamper detection work?
A: Each block's hash includes its data AND the previous block's hash. Changing any value breaks the chain — just like Bitcoin.

Q: What hashing algorithm?
A: SHA-256 via the browser's native crypto.subtle API — no external library.

Q: Is this the same as blockchain in industry?
A: Same cryptographic principle (Merkle chain of hashes). This demo adds GUN for the real-time P2P sync layer.