Write a contract. Deploy it from the wallet.
The editor and the Solidity compiler stay in this browser. The wallet signs the deploy. A deploy spends one XMSS leaf. A call that changes the contract spends another. A read does not.
Each deploy and each state-changing call spends one XMSS leaf. The wallet asks before it signs.
Not connected.
What this page does
Solidity 0.8.38 compiles in this browser. It is a separate program, loaded from the Solidity release files. The bytecode uses the Paris instruction set. This page is not a second chain, and it does not create its own accounts.
The wallet must be the Kalyx wallet for Chrome, Brave, or Firefox. It answers on chain 21520. Addresses are shown as KAL. A successful deploy, then a later call from this same page, is the proof that the chain accepted the bytecode.
The receipt and the logs are on the public testnet. Open the contract address in the explorer after it is mined. This page does not step through execution, because the public node does not offer traces.