Implement vault doors. Vault doors would be the entrance of underground vaults.
Vault 15 from Fallout 1
The vault area would be similar to classic dungeon crawler games in design, and there would be interesting items inside the vault, however, the vault areas would be dangerous. There could be mutated creatures inside the vault. And there would be radiation, which would create memory corruption.
Items inside the vault could be ammunition for the Mortar Hardware (#20) and Uranium cells for the Nuclear Power Plant structure (#38).
Vault doors could be password protected, which would require some hacking to unlock. Players could obtain the password by sniffing the Radio Frequencies (#32) or by brute-force. Vault Door password could be traded by players.
- Mine Map