Your first contract — Hello Solidity

solidity
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

contract Hello {
    string public greeting;

    constructor(string memory _greeting) {
        greeting = _greeting;
    }

    function setGreeting(string memory _greeting) public {
        greeting = _greeting;
    }
}

• SPDX comment: declares the open-source license. Required by the Solidity compiler (as a warning).
• pragma: the compiler version. ^0.8.24 means "0.8.24 or any 0.8.x newer".
• contract Hello: declares a contract named Hello. Contracts are like classes but their state lives on-chain forever.
• string public greeting: a state variable. public auto-generates a getter function.
• constructor: runs ONCE, at deployment. Initial setup.
• setGreeting: a mutating function. Changes on-chain state; costs gas to call.

Write a contract Counter with a uint256 public count and a function increment() that increases it by 1.