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

contract DailyCheckin {
    address public owner;
    uint256 public constant CHECKIN_FEE = 0.000019 ether; // 
    mapping(address => uint256) public lastCheckin; // 
    uint256 public totalCheckins; // 

    event Checkin(address indexed user, uint256 timestamp, uint256 amount);

    constructor() {
        owner = msg.sender;
    }

    // 
    function checkIn() external payable {
        require(msg.value == CHECKIN_FEE, "Must send exactly 0.0000055 ETH");
        
        // 
        uint256 lastCheckinTime = lastCheckin[msg.sender];
        if (lastCheckinTime > 0) {
            uint256 currentDay = block.timestamp / 1 days;
            uint256 lastCheckinDay = lastCheckinTime / 1 days;
            require(currentDay > lastCheckinDay, "Can only check-in once per day");
        }

        // 
        lastCheckin[msg.sender] = block.timestamp;
        totalCheckins++;

        // Emit event
        emit Checkin(msg.sender, block.timestamp, msg.value);
    }

    // 
    function withdraw() external {
        require(msg.sender == owner, "Only owner can withdraw");
        payable(owner).transfer(address(this).balance);
    }

    // 
    function getBalance() external view returns (uint256) {
        return address(this).balance;
    }
}

{
  "compilationTarget": {
    "DailyCheckin.sol": "DailyCheckin"
  },
  "evmVersion": "cancun",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": false,
    "runs": 200
  },
  "remappings": []
}