class BitcoinLikeBlockchain:
    def __init__(self):
        self.chain = []
        self.pending_transactions = []
        self.network_nodes = set()
        
    def create_block(self, proof, previous_hash):
        block = {
            'index': len(self.chain) + 1,
            'timestamp': time(),
            'transactions': self.pending_transactions,
            'proof': proof,
            'previous_hash': previous_hash
        }
        self.pending_transactions = []
        self.chain.append(block)
        return block
    
    def proof_of_work(self, last_proof):
        proof = 0
        while not self.valid_proof(last_proof, proof):
            proof += 1
        return proof

# Recent Open Source Contributions
blockchain_projects = {
    "bitcoin_core": "Optimized transaction validation",
    "lightning_network": "Payment channel implementations", 
    "smart_contracts": "Security audit tools",
    "consensus_algorithms": "PoW/PoS research"
}

for project, contribution in blockchain_projects.items():
    print(f"🚀 Contributed to {project}: {contribution}")