upgrade your doors. it wont prevent boarding but it will definitely slow down the enemies as they have to break down each door before moving between rooms. its an easy upgrade at the beginning of the game before you can get the more advanced items

Upgrade your doors. It won't prevent boarding but it will definitely slow down the enemies as they have to break down each door before moving between rooms. It's an easy upgrade at the beginning of the game before you can get the more advanced items.