        (basefee, gasExcess) = _calc1559BaseFee(config, _l1BlockId, _parentGasUsed);
        if (!skipFeeCheck() && block.basefee != basefee) {
            revert L2_BASEFEE_MISMATCH();
        
        if (gasExcess > 0) {
            // We always add the gas used by parent block to the gas excess
            // value as this has already happened
            uint256 excess = uint256(gasExcess) + _parentGasUsed;

            // Calculate how much more gas to issue to offset gas excess.
            // after each L1 block time, config.gasTarget more gas is issued,
            // the gas excess will be reduced accordingly.
            // Note that when lastSyncedBlock is zero, we skip this step
            // because that means this is the first time calculating the basefee
            // and the difference between the L1 height would be extremely big,
            // reverting the initial gas excess value back to 0.
            uint256 numL1Blocks;
            if (lastSyncedBlock > 0 && _l1BlockId > lastSyncedBlock) {
                numL1Blocks = _l1BlockId - lastSyncedBlock;
            }

            if (numL1Blocks > 0) {
                uint256 issuance = numL1Blocks * _config.gasTargetPerL1Block;
                excess = excess > issuance ? excess - issuance : 1;
            }

            gasExcess_ = uint64(excess.min(type(uint64).max));

            // The base fee per gas used by this block is the spot price at the
            // bonding curve, regardless the actual amount of gas used by this
            // block, however, this block's gas used will affect the next
            // block's base fee.
            basefee_ = Lib1559Math.basefee(
                gasExcess_, uint256(_config.basefeeAdjustmentQuotient) * _config.gasTargetPerL1Block
            );
        }
        if (_l1BlockId > lastSyncedBlock + BLOCK_SYNC_THRESHOLD) {
            // Store the L1's state root as a signal to the local signal service to
            // allow for multi-hop bridging.
            ISignalService(resolve("signal_service", false)).syncChainData(
                ownerChainId, LibSignals.STATE_ROOT, _l1BlockId, _l1StateRoot
            );
            lastSyncedBlock = _l1BlockId;
        }
