diff --git a/CCTF_Solutions_main/ctf.sol b/CCTF_Solutions_main/ctf.sol
index 7c0246d..2492187 100644
--- a/CCTF_Solutions_main/ctf.sol
+++ b/CCTF_Solutions_main/ctf.sol
@@ -11,7 +11,6 @@ import "./verifier.sol";
 
 contract CCTF9 is Verifier{
     address public admin;
-    uint256 public volStart;
     uint256 public volMaxPoints;
     bool public started;
 
@@ -61,34 +60,35 @@ contract CCTF9 is Verifier{
         started = false;
     }
 
+    /// transfers the admin privilege to _admin address
     function setAdmin(address _admin) external onlyAdmin {
         require(_admin != address(0));
         admin = _admin;
     }
 
+    /// can be used to set the status of the cctf to started or finished
     function setCCTFStatus(bool _started) external onlyAdmin {
         started = _started;
     }
 
+    /// creates a new capturable flag according to the arguments
     function setFlag(uint256 _flagId,Hash memory _flagHash, bool _onlyFirstSolver, uint256 _points, string memory _skill) external onlyAdmin{
         flags[_flagId] = Flag(_flagHash, _onlyFirstSolver, _points, _skill);
         emit FlagAdded(_flagId, _flagHash);
     }
 
-
-    function register(string memory _RTFM) external {
+    /// registers the caller as a player
+    function register() external {
         require(players[msg.sender].status == PlayerStatus.Unverified, 'Already registered or banned');
-        require(keccak256(abi.encodePacked('I_read_it')) == keccak256(abi.encodePacked(_RTFM)));  // PoW can be used for harder challenges, this is Entry!
         players[msg.sender].status = PlayerStatus.Verified;
     }
-
+    /// sets the player's status either to Unverified, Verified or Banned
     function setPlayerStatus(address player, PlayerStatus status) external onlyAdmin {
         players[player].status = status;
     }
 
 
     ////////// Submit flags
-    mapping(bytes32 => bool) usedNs;                       // Against replay attack (we only check message signer)
     mapping (address => mapping (uint256 => bool)) Solves;     // address -> challenge ID -> solved/not
     uint256 public submission_success_count = 0;               // For statistics
 
@@ -104,9 +104,9 @@ contract CCTF9 is Verifier{
             inputs[8+i] = addr[i];
         }
         bool valid = verifyTx(p,inputs);
-        require(valid, "Your proof is invalid");
-
+        assert(valid);
 
+        require(!Solves[msg.sender][_submitFor]); // can't submit the same flag multiple times
         Solves[msg.sender][_submitFor] = true;
         players[msg.sender].points += flags[_submitFor].points;
         players[msg.sender].points = players[msg.sender].points < volMaxPoints ? players[msg.sender].points : volMaxPoints;
@@ -119,11 +119,15 @@ contract CCTF9 is Verifier{
         emit FlagSolved(_submitFor, msg.sender);
     }
 
-
+    /// maps an address to unsigned int
     function addressToUint32 (address _addr) public pure returns (uint32[5] memory)
     {
         uint256 targetUint = uint256(uint160(_addr));
-        uint32[5] memory addr = [uint32(targetUint/4294967296**4),uint32(targetUint/4294967296**3),uint32(targetUint/4294967296**2),uint32(targetUint/4294967296),uint32(targetUint)];
+        uint32[5] memory addr = [uint32(targetUint/4294967296**4),
+                                uint32(targetUint/4294967296**3),
+                                uint32(targetUint/4294967296**2),
+                                uint32(targetUint/4294967296),
+                                uint32(targetUint)];
         return addr;
     }
 
@@ -143,4 +147,4 @@ contract CCTF9 is Verifier{
     function getFlag(uint256 id) external view returns (Flag memory) {
         return flags[id];
     }
-}
\ No newline at end of file
+}