Update Solidity Version and Refactor Contracts to Remove SafeMath Redundancy

contracts/src/attacks/AlienCodexAttack.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity ^0.5.0;
+pragma solidity ^0.8.0;
 
 import "../levels/AlienCodex.sol";
 

contracts/src/attacks/HigherOrderAttack.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.6.12;
+pragma solidity ^0.8.0;
 
 contract HigherOrderAttack {
     function encodedData() public pure returns (bytes memory) {

contracts/src/helpers/Ownable-05.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.8.0;
 
 /**
  * @dev Contract module which provides a basic access control mechanism, where

contracts/src/levels/AlienCodex.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity ^0.5.0;
+pragma solidity ^0.8.0;
 
 import "../helpers/Ownable-05.sol";
 

contracts/src/levels/AlienCodexFactory.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.5.0;
+pragma solidity ^0.8.0;
 
 import "./base/Level-05.sol";
 import "./AlienCodex.sol";

contracts/src/levels/Fallout.sol

@@ -1,7 +1,6 @@
 // SPDX-License-Identifier: MIT
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
-import "openzeppelin-contracts-06/math/SafeMath.sol";
 
 contract Fallout {
     using SafeMath for uint256;
@@ -21,7 +20,7 @@ contract Fallout {
     }
 
     function allocate() public payable {
-        allocations[msg.sender] = allocations[msg.sender].add(msg.value);
+        allocations[msg.sender] = allocations[msg.sender] + (msg.value);
     }
 
     function sendAllocation(address payable allocator) public {

contracts/src/levels/FalloutFactory.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
 import "./base/Level-06.sol";
 import "./Fallout.sol";

contracts/src/levels/HigherOrder.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.6.12;
+pragma solidity ^0.8.0;
 
 contract HigherOrder {
     address public commander;

contracts/src/levels/HigherOrderFactory.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.6.12;
+pragma solidity ^0.8.0;
 
 import "./base/Level-06.sol";
 import "./HigherOrder.sol";

contracts/src/levels/Reentrance.sol

@@ -1,15 +1,14 @@
 // SPDX-License-Identifier: MIT
-pragma solidity ^0.6.12;
+pragma solidity ^0.8.0;
 
-import "openzeppelin-contracts-06/math/SafeMath.sol";
 
 contract Reentrance {
     using SafeMath for uint256;
 
     mapping(address => uint256) public balances;
 
     function donate(address _to) public payable {
-        balances[_to] = balances[_to].add(msg.value);
+        balances[_to] = balances[_to] + (msg.value);
     }
 
     function balanceOf(address _who) public view returns (uint256 balance) {

contracts/src/levels/ReentranceFactory.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
 import "./base/Level-06.sol";
 import "./Reentrance.sol";

contracts/src/levels/Token.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
 contract Token {
     mapping(address => uint256) balances;

contracts/src/levels/TokenFactory.sol

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
 import "./base/Level-06.sol";
 import "./Token.sol";

contracts/src/levels/base/Level-05.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity ^0.5.0;
+pragma solidity ^0.8.0;
 
 import "../../helpers/Ownable-05.sol";
 

contracts/src/levels/base/Level-06.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity ^0.6.0;
+pragma solidity ^0.8.0;
 
 import "openzeppelin-contracts-06/access/Ownable.sol";