contract from our solidity 102 workshop at eth denver 2023

ponzi.sol

pragma solidity ^0.8.19;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

contract Farm{
   //track time of last deposit
   //block.timestamp
   mapping(address user => uint timestamp) public timeOfLastDeposit;

   //track how much deposited
   mapping(address user => uint balance) public userBalances;

   // create instance of ERC20 tokens
    address public rewardTokenAddress;
    address public lockedTokenAddress;
    IERC20 rewardToken;

        constructor(address _rewardTokenAddress, address _lockedTokenAddress){
            lockedTokenAddress = _lockedTokenAddress;
            rewardTokenAddress = _rewardTokenAddress;

            rewardToken = IERC20(rewardTokenAddress);
        
        }

        function deposit(uint amount) public{
            //take tokens from user and move to this contract
            IERC20 lockedToken = IERC20(lockedTokenAddress);
            lockedToken.transferFrom(msg.sender, address(this), amount);
            
            //update balance of user
            require(userBalances[msg.sender] + amount >= userBalances[msg.sender], "overflow???? how did you even do this?");
            userBalances[msg.sender] += amount;

            //update timestamp of last deposit
            timeOfLastDeposit[msg.sender] = block.timestamp;
        }

        function claim() public{
            //calculate how much you can claim
            uint timePassed = block.timestamp - timeOfLastDeposit[msg.sender];
            uint reward = timePassed * userBalances[msg.sender] * 10000; 
            if(userBalances[msg.sender] > 100000){
                reward = reward * 2;
            }

            //transfer to the claimer
            rewardToken.transferFrom(address(this), msg.sender, reward);

            //update time of last deposit
            timeOfLastDeposit[msg.sender] = block.timestamp;
        }
}