9. Complete but small subsystems for adventuring in dungeons and the wilderness
The near-boardgame nature of B/X means that it has tiny subsystems that cover exploring dungeons and the wilderness. Many of these come directly from OD&D's The Underworld & Wilderness Adventures but are either more clearly written or more discrete.
Examples of these subsystems are:
1. Resting - After moving for 5 turns, you must rest for 1 turn. (B19)
2. Opening stuck doors (B21)
3. Finding secret doors (B21)
4. Listening at doors (B21)
5. The whole "Order of Events in One Game Turn" (B23)
6. Wandering Monsters (B53)
Exploring the Wilderness
1. The "Order of Events in One Game Day" (X23)
2. the Evasion Table (X23)
3. Foraging (X51)
4. Becoming Lost (X56)
5. Castle Encounters (X59)
6. Wilderness Encounters (X57)
Many of these subsystems may defeat verisimilitude (something I rarely if ever strive for in my games). Why are all of the doors in the dungeon stuck? Why did the patrol of medium horsemen chase us from the castle?
Because the rules say so or because I rolled it on a table.
Why do you have to pay $350 rent if you land on Park Place? Because the rules say so.
These rules/subsystems make the game very easy to run.