This is a 2D companion to the 3D Blockchain Consensus simulator. It keeps the same real mechanics — a toy but genuine string-hash of each block's data, previous hash and nonce, a real proof-of-work nonce search against an adjustable difficulty target, and a real longest-chain fork-resolution rule — drawn as the canonical chain-of-linked-boxes diagram used to teach blockchain consensus.
Use Mine new block to run one real nonce search and append a block to the chain, or flip Auto-mine to keep mining continuously. Create fork spawns a rival branch off the current tip's parent that mines in parallel with its own nonce search; whichever branch pulls ahead in height becomes canonical, and the losing branch's blocks are marked orphaned — exactly the rule real proof-of-work networks use to agree on a single history.