Blockchain-on-Blockchain (BOB) is a new blockchain built on top of another blockchain called ICP. It's like a special layer on an existing system. BOB creates a secure digital record book that uses ICP's network for safety. BOB uses a system called 'proof-of-on-chain-work': You deploy your own smart contract (canister) at bob.fun. This program solves math problems (hashes). Main computers (mother nodes) give out these problems. Miners solve the problems and tell the mother node. If correct, the mother node adds a new block to the blockchain. The winning miner gets BOB tokens as a reward.