Created using remix-ide: Realtime Ethereum Contract Compiler and Runtime. Load this file by pasting this gists URL or ID at https://remix.ethereum.org/#version=soljson-v0.8.16+commit.07a7930e.js&optimize=false&runs=200&gist=

contracts..._ownable.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

contract Ownable {

address public owner; 
uint public counter; 
uint public counterPublic;

constructor () {
    owner = msg.sender; //set the owner at deploy time
}

modifier isOwner(address _owner) {
    require(_owner == owner, "You are not the owner");
    _;
}

function onlyOwnercanIncrease() external isOwner(msg.sender) {
    counter += 1;
}  

function transferOwnership(address _newOwner) external isOwner(msg.sender) {
    require (_newOwner != address(0), "Set a valid address");
    owner = _newOwner;
}

function publicFunction() external {
    counterPublic += 1;
}

}