Hey, this is a great question and actually you've hit on a legit bug here. Currently, enemies spawn 10 to 15 tiles from your base in a random direction. That was fine for the early development of the game but it's absolutely not intended and is something I've simply failed to spot until now. So I'm sorry about this bug! But I am fixing it right now. If you have an impenetrable base or even just a sprawling base, enemies will come "from the north" (or whatever direction) definitely from outside of it, rather than just spawning unfairly in an immersion-destroying kind of way. This will be in the 0.3.7 patch, coming out very shortly!
