pragma solidity ^0.4.25;

contract WorldToken {

    string public name = "World Shared Drone";     
    string public symbol = "WSDE";           
    uint256 public decimals = 6;           

    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;
    
     

    uint256 public totalSupply = 0;
    bool public stopped = false;

    uint256 constant valueFounder = 420000000000000;
    address owner = 0x0;

    modifier isOwner {
        assert(owner == msg.sender);
        _;
    }

    modifier isRunning {
        assert (!stopped);
        _;
    }

    modifier validAddress {
        assert(0x0 != msg.sender);
        _;
    }

    function WorldToken(address _addressFounder) {
        owner = msg.sender;
        totalSupply = valueFounder;
        balanceOf[_addressFounder] = valueFounder;
        Transfer(0x0, _addressFounder, valueFounder);
    }

    function transfer(address _to, uint256 _value) isRunning validAddress returns (bool success) {
        require(balanceOf[msg.sender] >= _value);
        require(balanceOf[_to] + _value >= balanceOf[_to]);
        balanceOf[msg.sender] -= _value;
        balanceOf[_to] += _value;
        Transfer(msg.sender, _to, _value);
        return true;
    }

    function transferFrom(address _from, address _to, uint256 _value) isRunning validAddress returns (bool success) {
        require(balanceOf[_from] >= _value);
        require(balanceOf[_to] + _value >= balanceOf[_to]);
        require(allowance[_from][msg.sender] >= _value);
        balanceOf[_to] += _value;
        balanceOf[_from] -= _value;
        allowance[_from][msg.sender] -= _value;
        Transfer(_from, _to, _value);
        return true;
    }

    function approve(address _spender, uint256 _value) isRunning validAddress returns (bool success) {
        require(_value == 0 || allowance[msg.sender][_spender] == 0);
        allowance[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    function stop() isOwner {
        stopped = true;
    }

    function start() isOwner {
        stopped = false;
    }

    function setName(string _name) isOwner {
        name = _name;
    }

    function burn(uint256 _value) {
        require(balanceOf[msg.sender] >= _value);
        balanceOf[msg.sender] -= _value;
        balanceOf[0x0] += _value;
        Transfer(msg.sender, 0x0, _value);
    }

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}