Coinbase transactions

Every block also pays a new reward to the miner. Balances are worked out by replaying every transaction from the first block.

Not the company. In Bitcoin, the “coinbase transaction” is the first transaction in every block: it creates brand-new coins and pays them to the miner who found the block. It is just a name for that special transaction. The crypto exchange Coinbase has no connection to this page. It took its name from the term, and it buys, sells and holds crypto for customers; it does not have its own blockchain.

Try this

Look at the balances line above each peer. Where did Anders’ money come from?
Make someone in block 2 send more than they have. Their name turns red – the money isn’t there.
Change who receives the coinbase reward in block 5 and watch the balances move.
Try changing an amount to 0 or a negative number.

Puts everything back as it was.

Based on the blockchain demo by Anders Brownworth (source, MIT licence – see licence). Rebuilt here as a self-contained page; this copy runs entirely in your browser and sends nothing anywhere.