practices.sol

//SPDX-License-Identifier: MIT

pragma solidity 0.8.7;

contract CountAfterSeconds{
    uint public count;
    uint today;

    constructor(){
        today = block.timestamp;
    }

    function add() public{
        require(block.timestamp <= today + 30 seconds);
        count++;
    }

    function dec() public{
        require(block.timestamp <= today + 30 seconds);
        count--;
    }

}