Entering and digging
An entrance connects places; it is not merely a hole in the ground.
At a reachable entrance, [Enter] switches between the surface and its linked nest. Portals instead connect two underworlds. Their destination is fixed; a visible entrance does not automatically lead to the nest the camera last showed.
What stops a shaft
Rock, the map edge, portals and protected ceiling areas limit excavation. An unreachable destination or broken route can also stop the work. A paused digging order does not resume as a teleport: the slime remains where it actually reached. For each further section, route, energy and diggable ground must still align.
An open ring remained around the new shaft even after the rain. No mushroom obscured the entrance.
