Playcoin

Bloxxgame started in 2018 as a hands-on classroom game that was a lot of fun for everyone. We called it “Playcoin” back then. The intention was to make the mechanism of securing transactions in the blockchain visible and thus understandable. The challenge lay in balancing clarity and precision. Clarity needs simplicity, while precision requires detailed explanations. The learning objective was: “How can I own something stored digitally and send it via the Internet without it being stolen?” It should also explain why a blockchain token cannot be copied or replicated.

Simplifying to understand

With these goals in mind, we decided that understanding hashing and signing is essential. To facilitate this, we developed a simple and very insecure “hashing and asymmetric encryption algorithm” that could be easily performed manually with a piece of paper.

Playcoin’s signing algorithm could only sign numbers.

Playcoin explained the principles of Bitcoin, so we also needed a mempool and the UTXO pool. For mining, we used dice to introduce randomness to the hashing algorithm of blocks.

Classroom teaching

A group of students worked together, each group representing a node that could create and send transactions and blocks. Playcoin was an engaging group game because mining required cooperation among group members. They had to update their mempool and UTXOs and simultaneously create a new valid block with at least two transactions from the mempool before another group could do so.

The teacher added new transactions to the mempool, sometimes overspending, double spending, or including invalid signatures. The proof-of-work concept of Bitcoin was illustrated in Playcoin by rolling 4 dice. This task was used to find a nonce that would give the block header hash the correct difficulty. A particular highlight was the consensus algorithm, which turned the classroom into an exciting competitive arena. Each group first checked a new block for validity: no double spends, valid signatures in the transactions, correct Merkle root, and block hash including difficulty. Only then could they build and publish their own new block.

Limitations of Playcoin

The limitations of Playcoin lay in its cumbersome algorithms and the time required to start and play the game. This led to the idea of introducing a software tool to overcome these limitations. Read the article about Bloxxgame 1 to find out how we developed a software game from the learnings of Playcoin.