Stake.sol

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract Staking {
    mapping(address => uint256) balances;
    uint256 public deadline = 0;
    event Stake(address sender, uint256 amount);

    function stake() public payable {
        require(msg.value > 0, "Input value");
        require(block.timestamp > deadline, "Wait until 30sec");
        balances[msg.sender] += msg.value;
        emit Stake(msg.sender, msg.value);
        updateDeadline(block.timestamp + 30 seconds);
    }

    function withdraw() public payable {
        require(block.timestamp > deadline, "");
        require(balances[msg.sender] > 0, "No amount staked");
        payable(msg.sender).transfer(balances[msg.sender]);
    }

    function updateDeadline(uint256 _deadline) private {
        deadline = _deadline;
    }

    function timeLeft() public view returns (uint256) {
        return deadline - block.timestamp;
    }
}