What?
Why the hell would we make it defensive? I made the ballistas so we don't immediately get slaughtered when enemies come around. If you can't fire them correctly then calm down.
The bridges were going to be hooked up to two pressure plates but I ran out of time. The giant space was enclosed at the start for a defense before we finished the main wall, why the hell WOULDN'T we have huge farms? Food is needed.
Ballistas in a tight battery on about tenth year of the fort is an efficient perk to defence. Three ballistas on sides of the fort, one of them not twenty tiles away from an edge, all three without any supporting infrastructure (such as AMMO STOCKPILES) on second year is madness. In a negative sense.
If you wanted to make bridges simply disappear, you could have done it with one single big one instead of TWELVE small ones. Or go with traps. As is, it is a waste of mechanisms and (IIRC) FPS.
Enclosing such a giant space at the start which you weren't going to use (and there was no way you could have used that much by second year) is simply a waste of resources and time (especially considering a half of it is WOODEN).
The farms are good. However, the larger the farms, the more time dwarves spend planting... plants, the less time they have to gather the planted ones. In other words, a waste of space and time.
And finally, in two years you have done less than many people do in their first month. Just for future reference, take a look at
The New Eternal Halls on DFMA. Yes, that fort is only two years old. Yes, there is a legendary dining room, every kind of workshop, personal bedrooms for every dwarf, every surface smoothed and most of them engraved, caverns breached and a nice economy established. Now compare it with this fort.
Sorry if that came out harsh. Still, it's the truth.