Manuel Sample contract

pragma solidity ^0.8.0;

contract Token {
    string public name = "Manuel";
    string public symbol = "MKPA";
    uint256 public totalSupply = 1000000;
    uint256 public decimals = 18;
    mapping(address => uint256) balances;
    
    constructor() {
        balances[msg.sender] = totalSupply;
    }
    
    function buyTokens(uint256 amount) public {
        require(amount > 0, "Amount should be greater than 0");
        require(balances[msg.sender] + amount <= totalSupply * 30 / 100, "more than maximum 30% of total supply");
        
        balances[msg.sender] += amount;
        totalSupply -= amount;
    }
    
    function balanceOf(address account) public view returns (uint256) {
        return balances[account];
    }
}