CTF Levels

Level_0_Practice.sol

pragma solidity 0.6.0;

contract Level_0_Practice {
	
	bool public levelComplete;
	uint8 answer;

	constructor() public {
        levelComplete = false;
        answer = 42;
    }

    function completeLevel(uint8 n) public payable {
        if (n == answer) {
            levelComplete = true;
        }
    }
	
}

Level_1_Brute_Force.sol

pragma solidity 0.6.0;

contract Level_1_Brute_Force {

    bool public levelComplete;
    bytes32 public answer;

    event Guess(bytes32 _guess);

    constructor() public {
        levelComplete = false;
        answer = 0x04994f67dc55b09e814ab7ffc8df3686b4afb2bb53e60eae97ef043fe03fb829;
    }

    function completeLevel(uint8 n) public {
        bytes32 _guess = keccak256(abi.encodePacked(n));
        emit Guess(_guess);
        require(_guess == answer);
        levelComplete = true;
    }
}

Level_2_Reentrancy.sol

pragma solidity 0.6.0;

contract Level_2_Reentrancy {
    string constant name = "Token";
    string constant symbol = "T";
    uint8 constant decimals = 18;
    uint public totalSupply;
    bool public levelComplete;

    mapping (address => uint256) balances;

    event Transfer(address indexed _from, address indexed _to, uint256 _value);

    constructor () public payable {
    	require(msg.value >= 1 ether);
        totalSupply = msg.value;
        levelComplete = false;
    }

    function balanceOf(address _owner) public view returns (uint256 balance) {
        return balances[_owner];
    }

    function deposit() public payable returns (bool success) {
        if (balances[msg.sender] + msg.value < msg.value) return false;
        if (totalSupply + msg.value < msg.value) return false;
        balances[msg.sender] += msg.value;
        totalSupply += msg.value;
        return true;
    }

    function withdraw(uint256 _value) public payable returns (bool success) {
        if (balances[msg.sender] < _value) return false;
        msg.sender.call.value(_value)("");
        balances[msg.sender] -= _value;
        totalSupply -= _value;
        return true;
    }

    function transfer(address _to, uint256 _value) public returns (bool success) {
        if (balances[msg.sender] < _value) return false;
        if (balances[_to] + _value < _value) return false;
        balances[msg.sender] -= _value;
        balances[_to] += _value;
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    function completeLevel() external {
    	require(balances[msg.sender] > totalSupply || totalSupply < 1000000000000000000);
    	levelComplete = true;
    }

}

Level_3_Global_Functions.sol

pragma solidity 0.6.0;

contract Level_3_Global_Functions {
    bytes32 guess;
    uint256 settlementBlockNumber;

    uint public totalSupply;
    bool public levelComplete;

    function guessTheFutureHash(bytes32 hash) public payable {
        guess = hash;
        settlementBlockNumber = block.number + 1;
    }

    function completeLevel() external {
    	require(block.number > settlementBlockNumber);
    	bytes32 answer = blockhash(settlementBlockNumber);
    	require(guess == answer);
    	levelComplete = true;
    }
}