The player picks a network, and the plugin creates a payment session. The amount is your price plus 4 extra digits that encode the item code and a random number: 4.99 → 4.993742.
The game watches the chain for a transfer of exactly that amount to your wallet. A transaction hash reported by the browser page, or pasted by the player, is checked directly instead. On Arc it reads the Transfer events of Arc's system emitter (0xffff…fffe), which logs every USDC move, a native send or an ERC-20 transfer, once each, in 18 decimals.
After enough confirmations (blocks on top of the payment's block; one on Arc, whose blocks are final; on Solana, once the transaction is finalized), the transfer is stored as a receipt in persistent. owns() reads receipts, which are re-verified on-chain at each launch.
Restore reads any transaction hash back from the chain and decodes the item from its amount.