Fun.xyz is a platform that offers Checkout, a solution enabling users to execute on-chain actions using various payment methods, including EVM tokens, Solana wallets, centralized exchanges, and credit/debit cards. The system comprises a liquidity aggregator, routing engine, and SDK, facilitating seamless transactions across multiple chains. Checkout's routing engine supports batched smart contract interactions and ensures transaction certainty through retries and gas fee coverage. The SDK integrates with applications to optimize conversion rates and user experience.