That moment when you suddenly slip, cross a line. The chemical defence lines you've carefully erected come crumbling down. What seemed to be an urban paradise washed clean by the light of a new day is now just another beleaguered sward of green in a shabby inner city.

You have two options: you can make a run for it back to the cocoon you've carefully prepared for this moment; or you can stay, wallow, experience - above all, hope. Never forget, other cocoons are available.

Within those two options lie two further. Do you try to shore up the crumbling defences or do you accept that the citadel is breached? And if you refuse to succumb to the comedown you know is inevitable, do you call on more of the same troops you've used previously or start a new front? If you've relied on the infantry so far, maybe it's time to call on the airborne division.

Choices.

There are more to be made. If you could map them out, they'd flow down the page like some Darwinian cascade. But unlike the evolution of species, there are no dead ends - except literally, and I'll presume that you can see the dragons lurking at the entrances to those and pass by - until one day the demon behind you is close enough for you to take a wrong turning, or maybe to think the bastion down that path will protect you yet not ensnare you. Maybe you're right.

No, most of the paths have exit points along them to allow you to hop to another branch. The choices don't reduce as you make them, their number grows at a seemingly exponential rate made comprehensible by your own personal template of what is and isn't acceptable. A small detail of the picture may look like a simple inverted tree, but the bigger picture reveals a messy, hyperlinked and interleaved web of connections, like a brain from which the enabling flesh has been removed leaving only the skein of electrical and chemical signals.

And the Big Picture? Perhaps trying to get a glimpse of that is how you find yourself faced with these choices, trying to pull back the curtains from the 4:3 of the advert for your local tandoori to the 70mm glory of the main feature. You'll only ever catch a glimpse and of that you can't ever be certain, but if you build up enough perspectives you might be able to hold on to an image even if you can't express it.

Or you could try one of the off-the-shelf models of the Big Picture, but that would take faith and that's sometimes in short supply at these moments of half-emptiness as the city comes to life.