Root + Impact

The root cause lies in a logic inversion in the claimThrone() function. Instead of rejecting calls from the current king, the contract mistakenly rejects everyone else. As a result, no one can claim the throne except the existing king (initially address(0)) — who is disallowed from reclaiming by design. This creates a logic contradiction and breaks the core flow of the game.

The impact is critical: the game becomes non-functional after the deployment, halting all progression. Players are unable to participate, and the owner cannot reset the game until a winner is declared — which can never happen if no one can claim.

Description

Affected code:
Game.sol::claimThrone()

• Normally, players can claim the throne if they are not already the current king, by paying the current claimFee.

• The claimThrone() function incorrectly prevents all valid claims by requiring the caller to be the current king, rather than not the current king.

Risk

Likelihood:

The likehood is High because:

• Always occurs after the first throne claim is made by any non-zero address.

• Prevents all subsequent players from interacting with the game.

Impact:

The impact is high because the issue:

• Completely halts the core game mechanic.

• Causes a Denial-of-Service and breaks user flow.

Proof of Concept

Add the test bellow inside the Game.t.sol and run the test use the following script:

Result:

Recommended Mitigation

Inisde the Game.sol::claimThrone() invert the require statement from == to != to ensure only different user can claim the throne from the previous one.