What The Block – Onchain

What the Block – Onchain is a hybrid physical-digital multiplayer game that links tangible interaction to live blockchain transactions. Players use LEGO-based components, including NFC-enabled tokens and physical transaction records, to negotiate trades and assemble blocks. These physical actions trigger transactions on the Ethereum Sepolia network. By coupling tangible play with onchain execution, the system makes core processes physically inspectable and digitally consequential, inviting participants to enact the role of infrastructure operators.

The game scaffolds complexity across four rounds, each ending with a moderated reveal mapping enacted actions onto concepts and terminology.

Resource tokens are implemented as custom-designed, 3D-printed 2×2 LEGO bricks, each housing a unique 10 mm NFC tag. The bricks have an extended height of 11.8 mm to accommodate an embedded tag, with a side-mounted pocket and circular window aligned to the tag position. The pocket fits a round NTAG215 flexible NFC sticker, enabling reliable scanning while keeping the tag physically integrated into the token.

Two NFC reader terminals combine XIAO ESP32S3 microcontrollers and PN532 readers, streaming scan events over USB serial to a connected laptop. Designed in Fusion 360 and 3D printed in PLA, each terminal houses a custom PCB milled on a Carvera milling machine, a 16×2 LCD display, and an NFC reader module. Players scan their physical wallets and the tokens being exchanged, followed by a final confirmation scan. Each action provides immediate visual and auditory feedback.

The laptop runs a Python controller that parses tag IDs, enforces a lightweight trade state machine, and triggers onchain execution when a trade is confirmed. It classifies scanned identifiers as player, resource, or control tags and maintains the active player, each player’s pending resource selection, and resource identifiers already spent in the current round. This prevents reuse of the same physical token, providing a physical double-spend analogue. Control tags allow cancelling the current trade state or ending a round.

For each transfer, the controller submits an Ethereum transaction on Sepolia using Web3.py via an Infura RPC gateway. Transactions follow the EIP-1559 format and include the recipient wallet address, a small ETH amount or zero for a pure log, and a text-encoded payload storing the sender, recipient, and resource. Each transaction is signed locally using the sender’s private key, broadcast to the network, and its transaction hash returned for verification. A Dune dashboard displays wallet addresses, values, and timestamps, reinforcing the link between physical and digital actions.

Each player maintains a parallel physical record of all transactions, reflecting the distributed nature of blockchain ledgers. Players stack recorded transactions on 8×8 LEGO baseplates to construct proposed blocks. At the end of each round, one block is collectively confirmed using adapted Proof-of-Work or Proof-of-Stake mechanisms and placed onto the shared block builder, where blocks accumulate to form a physical blockchain.

The experience scaffolds complexity across four rounds, introducing trading, changing exchange conditions, new tokenised resources, and simple programmable rules using smart-contract cards. Each round concludes with a structured reveal mapping players’ actions onto blockchain concepts. An exploratory study with four blockchain novices found higher self-reported understanding and confidence, with participants reasoning about decentralisation, transparency, and adversarial behaviour using concepts encountered during play.