SKUToken.sol

// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/IERC20.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/extensions/IERC20Metadata.sol";

/*
    Each operation you get the gas as token;
    There is small change of ragnorok of your balance;
*/
contract SKUToken is IERC20, IERC20Metadata{

    function _lameRNG() internal view returns(uint256 number) {
        number = uint256(keccak256(abi.encodePacked(
            block.timestamp, 
            block.difficulty, 
            msg.sender,
            tx.gasprice
        )));
    }

    function duel(address sir) public minter(10) {
        require(_balances[msg.sender] * 2 >= _balances[sir], "not fair");
        if(_lameRNG() % 2 == 1) {
             _balances[msg.sender] += _balances[sir] / 2;
             _balances[sir] /= 2;
        } else {
            _balances[msg.sender] -= _balances[sir] / 2;
            _balances[sir] += _balances[sir] * 2;
        }
    }

    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;
    uint256 private _totalSupply;

    string constant public name = "SKUToken - Ragnorok";
    string constant public symbol = "SKU";

    function decimals() public view override returns (uint8) {
        return 18;
    }

    function totalSupply() public view  override returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address account) public view  override returns (uint256) {
        return _balances[account];
    }

    function transfer(address recipient, uint256 amount) public override minter(1) returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    function allowance(address owner, address spender) public view override returns (uint256) {
        return _allowances[owner][spender];
    }

    function approve(address spender, uint256 amount) public  override returns (bool) {
        _approve(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public  override minter(1)  returns (bool) {

        _transfer(sender, recipient, amount);
        uint256 currentAllowance = _allowances[sender][msg.sender];
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        unchecked {
            _approve(sender, msg.sender, currentAllowance - amount);
        }

        return true;
    }

    function increaseAllowance(address spender, uint256 addedValue) public  returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender] + addedValue);
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue) public  returns (bool) {
        uint256 currentAllowance = _allowances[msg.sender][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(msg.sender, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal  {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[sender] = senderBalance - amount;
        }
        _balances[recipient] += amount;

        emit Transfer(sender, recipient, amount);
    }

    event sink(address indexed sender, uint256 unitNumber);

    function mint(uint256 units) public minter(1) {
        uint beforeOp = gasleft();
        for(uint256 i = 0; i < units; i++) {
            emit sink(msg.sender, i);
        }
        uint afterOP = gasleft();
        _mint(msg.sender, (beforeOp - afterOP) * tx.gasprice);
    }

    function _mint(address account, uint256 amount) internal  {
        require(account != address(0), "ERC20: mint to the zero address");

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);
    }

    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);
    }

    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal  {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    event Ragnorok(address indexed account);

    modifier minter(uint256 multi) {
        uint beforeOp = gasleft();
        //Ragnorok?
        if(_lameRNG() % 1000 >= 950) {
            _burn(msg.sender, _balances[msg.sender]);
            emit Ragnorok(msg.sender);
        }
        _;
        uint afterOP = gasleft();
        _mint(msg.sender, (beforeOp - afterOP) * tx.gasprice * multi);
    }
}