The other day a big siege arrived at my fortress. Through management, I was able to capture a bunch of the invaders in a narrow, trap-lined hallway, then push the rest of them out with my military. Relaxing, I lower all my drawbridges, and a human caravan arrives. Suddenly, a vile force of darkness arives. What? Only a month passed between the two sieges, and the human caravan barely had time to get into the depot before the gate was closed, and I had to wall off the aforementioned trap hall. This siege is even bigger than the last, and includes the Afflicted Spider's war leader, so I dig in for the long haul. I know my military can crush any one of their three groups, but the trick is doing it. I come up with a plan to collapse a ceiling on the head of the war leader by pitting some animals into a previously excavated cave that did not connect to the main fort, waiting for them to attack the animals as goblins are wont to do, then using a triggered support to collapse onto the last two tiles connecting the ceiling to the mountain, thus collapsing the ceiling onto the goblins.
All this with an FPS of about 25. It took me a couple hours to figure out what to do and how to cause a collapse from above and inside, and by the time I had finished the human merchants had gone mad (no wonder dwarves are so weird, humans can only stay in these mines for so long before mental illness sets in) and literally moments after the support was connected to a lever the siege was lifted.
Sigh. Well, at least they left behind one of their mace lords in my cage traps. Stupid goblins.