contract Crowdsale is Pausable {
  using SafeMath for uint256;

  // The token being sold
  ERC20 public token;

  // Address where funds are collected
  address public wallet;

  // How many token units a buyer gets per wei
  uint256 public rate;

  // Amount of wei raised
  uint256 public weiRaised;
  
  // Crowdsale opening time
  uint256 public openingTime;
  
  // Crowdsale closing time
  uint256 public closingTime;

  // Crowdsale duration in days
  uint256 public duration;

  /**
   * Event for token purchase logging
   * @param purchaser who paid for the tokens
   * @param beneficiary who got the tokens
   * @param value weis paid for purchase
   * @param amount amount of tokens purchased
   */
  event TokenPurchase(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);

  constructor() public {
    rate = 4000;
    wallet = 0x3CB0F6d4Fc022348Cf75Cdb2C2E04492975e4d30;
    token = ERC20(0x0c537C661B28a4EF16AB27BEd46111473a6bd08d);
    duration = 120 days;
    openingTime = now;  // Determined by start()
    closingTime = openingTime + duration;  // Determined by start()
  }

  /**
   * @dev Returns the rate of tokens per wei at the present time.
   * Note that, as price _increases_ with time, the rate _decreases_.
   * @return The number of tokens a buyer gets per wei at a given time
   */
  function getCurrentRate() public view returns (uint256) {
        if (now <= openingTime.add(30 days)) return rate.add(rate*4/10);   // bonus 40% first 30 days
        if (now > openingTime.add(30 days) && now <= openingTime.add(60 days)) return rate.add(rate/5);   // bonus 20% first 30 days
        if (now > openingTime.add(60 days) && now <= openingTime.add(90 days)) return rate.add(rate/2);   // bonus 10% first 30 days
  }

  // -----------------------------------------
  // Crowdsale external interface
  // -----------------------------------------

  /**
   * @dev fallback function ***DO NOT OVERRIDE***
   */
  function () external payable {
    buyTokens(msg.sender);
  }

  /**
   * @dev low level token purchase ***DO NOT OVERRIDE***
   * @param _beneficiary Address performing the token purchase
   */
  function buyTokens(address _beneficiary) public payable {

    uint256 weiAmount = msg.value;
    _preValidatePurchase(_beneficiary, weiAmount);

    // calculate token amount to be created
    uint256 tokens = _getTokenAmount(weiAmount);

    // update state
    weiRaised = weiRaised.add(weiAmount);

    _processPurchase(_beneficiary, tokens);
    emit TokenPurchase(msg.sender, _beneficiary, weiAmount, tokens);

    _forwardFunds();
  }

  // -----------------------------------------
  // Internal interface (extensible)
  // -----------------------------------------

  /**
   * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met. Use super to concatenate validations.
   * @param _beneficiary Address performing the token purchase
   * @param _weiAmount Value in wei involved in the purchase
   */
  function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal whenNotPaused {
    require(_beneficiary != address(0));
    require(block.timestamp >= openingTime && block.timestamp <= closingTime);
  }

  /**
   * @dev Source of tokens. Override this method to modify the way in which the crowdsale ultimately gets and sends its tokens.
   * @param _beneficiary Address performing the token purchase
   * @param _tokenAmount Number of tokens to be emitted
   */
  function _deliverTokens(address _beneficiary, uint256 _tokenAmount) internal {
    token.transfer(_beneficiary, _tokenAmount);
  }

  /**
   * @dev Executed when a purchase has been validated and is ready to be executed. Not necessarily emits/sends tokens.
   * @param _beneficiary Address receiving the tokens
   * @param _tokenAmount Number of tokens to be purchased
   */
  function _processPurchase(address _beneficiary, uint256 _tokenAmount) internal {
    _deliverTokens(_beneficiary, _tokenAmount);
  }

  /**
   * @dev Override to extend the way in which ether is converted to tokens.
   * @param _weiAmount Value in wei to be converted into tokens
   * @return Number of tokens that can be purchased with the specified _weiAmount
   */
  function _getTokenAmount(uint256 _weiAmount) internal view returns (uint256) {
    uint256 currentRate = getCurrentRate();
    return currentRate.mul(_weiAmount);
  }

  /**
   * @dev Determines how ETH is stored/forwarded on purchases.
   */
  function _forwardFunds() internal {
    wallet.transfer(msg.value);
  }
  
  /**
   * @dev Checks whether the period in which the crowdsale is open has already elapsed.
   * @return Whether crowdsale period has elapsed
   */
  function hasClosed() public view returns (bool) {
    return block.timestamp > closingTime;
  }

  /**
   * @dev called by the owner to withdraw unsold tokens
   */
  function unsoldTokens() public onlyOwner {
    uint256 unsold = token.balanceOf(this);
    token.transfer(owner, unsold);
  }

}
function _forwardFunds() internal {
  wallet.transfer(msg.value);
}

/**
 * @dev Determines how ETH is stored/forwarded on purchases.
 */