function removePrize(uint16 _tileId, address _token, uint _tokenId) public isOwner {
        Prize[] storage prizeArr = prizes[_tileId];
        require(prizeArr.length > 0);

        for(uint idx = 0; idx < prizeArr.length; ++idx) {
            if(prizeArr[idx].tokenId == _tokenId && prizeArr[idx].token == _token) {
                delete prizeArr[idx];
                emit PrizeRemoved(_tileId, _token, _tokenId, block.timestamp);
            }
        }
    }