5.Port Certificate NFT(ERC721)

Port certificates are distributed to players by the port. Players can only purchase one certificate per port.

Obtaining Port Certificate: Purchase from port NPCs, at the cost of ETH/MTTs.

Port Certificate Functions:

1. Allows usage of the port's warehouse, factory, and shop.

2. Records player's warehouse, factory, and shop information at the port.

Port Certificate Fees:

Two ports are currently open: Pisa Port and Marseille Port. The fees for port vouchers are $5 for Pisa Port and $5.5 for Marseille Port.

The initial purchase of a monthly pass grants a validity period of 30 days.

After expiration, the factory, shop, warehouse, and shipyard will become unavailable.

Renewal rules:

Renewal is possible when there are 3 days remaining in the valid period. Renewal options are available for 30 days, 60 days, and 90 days.

The price for a 30-day renewal is calculated as 1 * (port certificate price + upgrade cost) / port certificate price.

The price for a 60-day renewal is calculated as 1.8 * (port certificate price + upgrade cost) / port certificate price.

The price for a 90-day renewal is calculated as 2.4 * (port certificate price + upgrade cost) / port certificate price.