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Airdrop.sol

pragma solidity ^0.4.16;


interface High4Teens {
    function transferFrom(address from, address to, uint tokens);
}

contract Airdrop {
    
    High4Teens public token;
    address public tokenHolder;
    uint amountToTransfer;
    
    function Airdrop(address addressOfToken, address addressOfHolder, uint fixedAmount){
        token = High4Teens(addressOfToken);
        tokenHolder = addressOfHolder;
        amountToTransfer = fixedAmount;
    }

    function drop() public {
      token.transferFrom(tokenHolder, msg.sender, amountToTransfer);
    }
}

Animal.sol

pragma solidity 0.5.1;

import './Ownable.sol';

contract AnimalContract is Ownable{
    
    event animalAdded(address owner, string animalName);
    
    enum AnimalType {DOG, CAT}
    
    struct Animal {
        string name;
        uint age;
        AnimalType animalType;
    }
    
    mapping (address => Animal[]) ownerToAnimals;
    
    function _addAnimal(string memory _name, uint _age, AnimalType _animalType) internal onlyOwner returns (uint) {  
        emit animalAdded(msg.sender, _name);
        return ownerToAnimals[msg.sender].push(Animal(_name, _age, _animalType)) - 1;
    }
    
    function getAnimal(uint _id) public view returns (string memory){
        return ownerToAnimals[msg.sender][_id].name;
    }
}

ballot.sol

pragma solidity >=0.4.22 <0.6.0;
contract Ballot {

    struct Voter {
        uint weight;
        bool voted;
        uint8 vote;
        address delegate;
    }
    struct Proposal {
        uint voteCount;
    }

    address chairperson;
    mapping(address => Voter) voters;
    Proposal[] proposals;

    /// Create a new ballot with $(_numProposals) different proposals.
    constructor(uint8 _numProposals) public {
        chairperson = msg.sender;
        voters[chairperson].weight = 1;
        proposals.length = _numProposals;
    }

    /// Give $(toVoter) the right to vote on this ballot.
    /// May only be called by $(chairperson).
    function giveRightToVote(address toVoter) public {
        if (msg.sender != chairperson || voters[toVoter].voted) return;
        voters[toVoter].weight = 1;
    }

    /// Delegate your vote to the voter $(to).
    function delegate(address to) public {
        Voter storage sender = voters[msg.sender]; // assigns reference
        if (sender.voted) return;
        while (voters[to].delegate != address(0) && voters[to].delegate != msg.sender)
            to = voters[to].delegate;
        if (to == msg.sender) return;
        sender.voted = true;
        sender.delegate = to;
        Voter storage delegateTo = voters[to];
        if (delegateTo.voted)
            proposals[delegateTo.vote].voteCount += sender.weight;
        else
            delegateTo.weight += sender.weight;
    }

    /// Give a single vote to proposal $(toProposal).
    function vote(uint8 toProposal) public {
        Voter storage sender = voters[msg.sender];
        if (sender.voted || toProposal >= proposals.length) return;
        sender.voted = true;
        sender.vote = toProposal;
        proposals[toProposal].voteCount += sender.weight;
    }

    function winningProposal() public view returns (uint8 _winningProposal) {
        uint256 winningVoteCount = 0;
        for (uint8 prop = 0; prop < proposals.length; prop++)
            if (proposals[prop].voteCount > winningVoteCount) {
                winningVoteCount = proposals[prop].voteCount;
                _winningProposal = prop;
            }
    }
}

ballot_test.sol

import "remix_tests.sol"; // this import is automatically injected by Remix.
import "./ballot.sol";

contract test3 {
   
    Ballot ballotToTest;
    function beforeAll () public {
       ballotToTest = new Ballot(2);
    }
    
    function checkWinningProposal () public {
        ballotToTest.vote(1);
        Assert.equal(ballotToTest.winningProposal(), uint(1), "1 should be the winning proposal");
    }
    
    function checkWinninProposalWithReturnValue () public view returns (bool) {
        return ballotToTest.winningProposal() == 1;
    }
}

Crowdsale.sol

pragma solidity ^0.4.16;

interface High4Teens {
    function transfer(address receiver, uint amount);
}

contract Crowdsale {
    
    address public beneficiary;
    uint public fundingGoal;
    uint public totalAmountRaised;
    uint public crowdSaleDeadline;
    uint public tokenPrice;
    High4Teens public token;
    
    mapping(address => uint) public balanceOf;
    
    bool fundingGoalReached = false;
    bool crowdSaleClosed = false;
    
    /**
     * Constructor
     * ifSuccessfulSendTo: Address where funds should be sent if sale reaches target
     * goalInEther: What is the target goal for the crowdsale in ethers.
     * durationInMinutes: How long will the crowdsale be running.
     * tokenPriceInEther: How much does each token cost
     * addressOfToken: Where is the token contract deployed.
     */
    function Crowdsale(
        address ifSuccessfulSendTo,
        uint goalInEther,
        uint durationInMinutes,
        uint tokenPriceInEther,
        address addressOfToken
    ) {
        
        beneficiary = ifSuccessfulSendTo;
        fundingGoal = goalInEther;
        crowdSaleDeadline = now + durationInMinutes * 1 minutes;
        tokenPrice = tokenPriceInEther * 1 ether;
        token = High4Teens(addressOfToken);

    }

    /**
     * Fallback function
     *
     * Default function which gets called when someone sends money to the contract. Will be used for joining sale.
     */
    function () payable {
        require(!crowdSaleClosed);
        uint amount = msg.value;
        balanceOf[msg.sender] += amount;
        totalAmountRaised += amount;
        token.transfer(msg.sender, amount/tokenPrice);
    }

    /**
     * Modifier used to check if deadline for crowdsale has passed
     */
    modifier afterDeadline() {
        if(now >= crowdSaleDeadline){
            _;
        }
    }

    /**
     * Check if the funding goal was reached. Will only be checked if afterDeadline modifier above is true.
     *
     */
    function checkGoalReached() afterDeadline {
        if(totalAmountRaised >= fundingGoal){
            fundingGoalReached = true;
        }
        crowdSaleClosed = true;
    }


    /**
     * Withdraw the funds
     *
     * Will withdraw the money after the deadline has been reached. If the goal was reached, only the owner can withdraw money to the beneficiary account.
     * If you goal was not reached, everyone who participated can withdraw their share.
     */
    function safeWithdrawal() afterDeadline {
        if(!fundingGoalReached){
            uint amount = balanceOf[msg.sender];
            balanceOf[msg.sender] = 0;
            if(amount > 0){
                if(msg.sender.send(amount)){
                    
                }
            }
        }
        if(fundingGoalReached && msg.sender == beneficiary){
            if(!beneficiary.send(totalAmountRaised)){
                fundingGoalReached = false;
            }
        }
    }
}

Dog.sol

pragma solidity 0.5.1;

import './Animal.sol';

contract DogContract is AnimalContract {
    
    modifier costs(uint amount){
        require (msg.value >= amount);
        _;
        if(msg.value > amount){
            msg.sender.transfer(msg.value - amount);
        }
    }
    
    function addDog(string memory _name, uint _age) public payable costs(500) returns (uint){
        return _addAnimal(_name, _age, AnimalType.DOG);
    }
    
    function getBalance() public view returns (uint) {
        return address(this).balance;
    }

}

DogInterface.sol

pragma solidity 0.5.1;

contract DogContract{

    function addDog(string memory _name, uint _age) public payable returns (uint);

    function getBalance() public view returns (uint);
}

contract ExternalContract {

    DogContract dc = DogContract(0x83171cf735D1BA4AAaf1571DE744697A8AFBA3Dd);

    function addExternalDog(string memory _name, uint _age) public payable returns (uint){
        return dc.addDog.value(msg.value)(_name, _age);
    }
    
    function getExternalBalance() public view returns (uint){
        return dc.getBalance();
    }
}

IntegetUnderOverFlow.sol

pragma solidity 0.5.1;

contract C {

    // (2**256 - 1) + 1 = 0
    function overflow() public pure returns (uint256 _overflow) {
        uint256 max = 2**256 -1;
        return max + 1;
    }

    // 0 - 1 = 2**256 - 1
    function underflow() public pure returns (uint256 _underflow) {
        uint256 min = 0;
        return min - 1;
    }
}

Ownable.sol

pragma solidity 0.5.1;

contract Ownable{
    
    address public owner;
    
    modifier onlyOwner(){
        require (msg.sender == owner);
        _;
    }
    
    constructor() public {
        owner = msg.sender;
    }
    
    function transferOwnership(address newOwner) public onlyOwner {
        // require(newOwner != address(0));
        owner = newOwner;
    }

}

SafeMathAdded.sol

pragma solidity 0.5.1;

library SafeMath {

  /**
  * @dev Multiplies two numbers, throws on overflow.
  */
  function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
    // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
    if (a == 0) {
      return 0;
    }

    c = a * b;
    assert(c / a == b);
    return c;
  }

  /**
  * @dev Integer division of two numbers, truncating the quotient.
  */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // assert(b > 0); // Solidity automatically throws when dividing by 0
    // uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
    return a / b;
  }

  /**
  * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
  */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  /**
  * @dev Adds two numbers, throws on overflow.
  */
  function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
    c = a + b;
    assert(c >= a);
    return c;
  }
}


contract C {
    using SafeMath for uint256;

    // (2**256 - 1) + 1 = 0
    function overflow() public pure returns (uint256 _overflow) {
        uint256 max = 2**256 -1;
        return max.add(1);
    }

    // 0 - 1 = 2**256 - 1
    function underflow() public pure returns (uint256 _underflow) {
        uint256 min = 0;
        return min.sub(1);
    }
}

Token.sol

pragma solidity ^0.4.18;

// ----------------------------------------------------------------------------
// High4Teens token contract
//
// Deployed to : 0xEb7208A7453dFC3C7380170A99fc5156A160Cd75
// Symbol      : H4T
// Name        : High4Teens
// Total supply: 100000000
// Decimals    : 18
//
// Enjoy.
//
// (c) by Moritz Neto with BokkyPooBah / Bok Consulting Pty Ltd Au 2017. The MIT Licence.
// ----------------------------------------------------------------------------


// ----------------------------------------------------------------------------
// Safe maths
// ----------------------------------------------------------------------------
contract SafeMath {
    function safeAdd(uint a, uint b) public pure returns (uint c) {
        c = a + b;
        require(c >= a);
    }
    function safeSub(uint a, uint b) public pure returns (uint c) {
        require(b <= a);
        c = a - b;
    }
    function safeMul(uint a, uint b) public pure returns (uint c) {
        c = a * b;
        require(a == 0 || c / a == b);
    }
    function safeDiv(uint a, uint b) public pure returns (uint c) {
        require(b > 0);
        c = a / b;
    }
}


// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
// ----------------------------------------------------------------------------
contract ERC20Interface {
    function totalSupply() public view returns (uint);
    function balanceOf(address tokenOwner) public view returns (uint balance);
    function allowance(address tokenOwner, address spender) public view returns (uint remaining);
    function transfer(address to, uint tokens) public returns (bool success);
    function approve(address spender, uint tokens) public returns (bool success);
    function transferFrom(address from, address to, uint tokens) public returns (bool success);

    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}


// ----------------------------------------------------------------------------
// Contract function to receive approval and execute function in one call
//
// Borrowed from MiniMeToken
// ----------------------------------------------------------------------------
contract ApproveAndCallFallBack {
    function receiveApproval(address from, uint256 tokens, address token, bytes data) public;
}


// ----------------------------------------------------------------------------
// Owned contract
// ----------------------------------------------------------------------------
contract Owned {
    address public owner;
    address public newOwner;

    event OwnershipTransferred(address indexed _from, address indexed _to);

    function Owned() public {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address _newOwner) public onlyOwner {
        newOwner = _newOwner;
    }
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        OwnershipTransferred(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}


// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals and assisted
// token transfers
// ----------------------------------------------------------------------------
contract High4Teens is ERC20Interface, Owned, SafeMath {
    string public symbol;
    string public  name;
    uint8 public decimals;
    uint public _totalSupply;

    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;


    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------
    function High4Teens() public {
        symbol = "H4T";
        name = "High4Teens";
        decimals = 18;
        _totalSupply = 100000000000000000000000000;
        balances[msg.sender] = _totalSupply;
        Transfer(address(0), msg.sender, _totalSupply);
    }


    // ------------------------------------------------------------------------
    // Total supply
    // ------------------------------------------------------------------------
    function totalSupply() public view returns (uint) {
        return _totalSupply  - balances[address(0)];
    }


    // ------------------------------------------------------------------------
    // Get the token balance for account tokenOwner
    // ------------------------------------------------------------------------
    function balanceOf(address tokenOwner) public view returns (uint balance) {
        return balances[tokenOwner];
    }


    // ------------------------------------------------------------------------
    // Transfer the balance from token owner's account to to account
    // - Owner's account must have sufficient balance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transfer(address to, uint tokens) public returns (bool success) {
        balances[msg.sender] = safeSub(balances[msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);
        Transfer(msg.sender, to, tokens);
        return true;
    }


    // ------------------------------------------------------------------------
    // Token owner can approve for spender to transferFrom(...) tokens
    // from the token owner's account
    //
    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
    // recommends that there are no checks for the approval double-spend attack
    // as this should be implemented in user interfaces 
    // ------------------------------------------------------------------------
    function approve(address spender, uint tokens) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        Approval(msg.sender, spender, tokens);
        return true;
    }


    // ------------------------------------------------------------------------
    // Transfer tokens from the from account to the to account
    // 
    // The calling account must already have sufficient tokens approve(...)-d
    // for spending from the from account and
    // - From account must have sufficient balance to transfer
    // - Spender must have sufficient allowance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transferFrom(address from, address to, uint tokens) public returns (bool success) {
        balances[from] = safeSub(balances[from], tokens);
        allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);
        Transfer(from, to, tokens);
        return true;
    }


    // ------------------------------------------------------------------------
    // Returns the amount of tokens approved by the owner that can be
    // transferred to the spender's account
    // ------------------------------------------------------------------------
    function allowance(address tokenOwner, address spender) public view returns (uint remaining) {
        return allowed[tokenOwner][spender];
    }


    // ------------------------------------------------------------------------
    // Token owner can approve for spender to transferFrom(...) tokens
    // from the token owner's account. The spender contract function
    // receiveApproval(...) is then executed
    // ------------------------------------------------------------------------
    function approveAndCall(address spender, uint tokens, bytes data) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        Approval(msg.sender, spender, tokens);
        ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data);
        return true;
    }


    // ------------------------------------------------------------------------
    // Don't accept ETH
    // ------------------------------------------------------------------------
    function () public payable {
        revert();
    }


    // ------------------------------------------------------------------------
    // Owner can transfer out any accidentally sent ERC20 tokens
    // ------------------------------------------------------------------------
    function transferAnyERC20Token(address tokenAddress, uint tokens) public onlyOwner returns (bool success) {
        return ERC20Interface(tokenAddress).transfer(owner, tokens);
    }
}