This started as some formatting cleanup but I've added a couple of
additional terrain features which can act as web support (stairs up
and ladder up).
The message "<Spider> spins a web" was given if you could detect or
sense <spider> rather than see it. I've changed that to only happen
if you see the new web appear rather than the critter spinning it
(it only becomes an unseen trap if you don't watch it appear).
After spinning a web, a spider can't spin another one until 4d4 moves
have elapsed. That seems suitable when the spider can be seen but
isn't really adequate throttling when the spider is far away--it can
end up spinning a lot of webs by the time you get to its vicinity.
Perhaps it shouldn't be able to spin a new web if there is already
one with N steps of its location?
projects / nethack / commit