I heard your presentation "Shaping Player Experience Through World Geometry" today...
I was working on a level / prop, and listening to WinAmp - and I have a huge collection of GDC audio clips mixed in with my music. So suddenly at random, this presentation of yours appeared. I'm guessing its a few years old now. No matter. (Didn't know your email address... So I thought this would do.)
And I thought of the language of geometric experience you presented, within the context of the campaign I'm about to release (www.preparetodrop.com). There's a video there. Anyway, it occurred to me that much of my level design coincidentally followed the same ideas of yourself and Kevin Lynch (the latter's from his book you cited, The Image Of The City) - without me really knowing crisply about these ideas.
(Danger: Mild spoilers ahead...)
The first level is a mix of node-structure and path-structure. The players, naive to the situation on Earth (having only recently arrived from out-system), come into a silent space station. Of course, it turns out infested with aliens. I tried to give a sense of a chase through a space station, with the main threat coming continually from *behind* the player (e.g. triggers that spawn aliens [out of vents, smashing through doors, etc] only *after* the last member of the team has passed). That's a real advantage of the top-down shooter: the ability for a player to move laterally - or even in reverse - while he watches his main danger zones.
Second level is an edge one: having escaped from the space station you land in a suburban office area, and running onto the green lawns you need to try to find the edges (fences, the comfort of which the aliens are programmed to deny you, by crawling right over them). The edges will lead you, eventually, to the objective.
Third level is a pit-of-doom one: you're on a train, and if you fall off, you're dead. So while the first level was extreme forward momentum, and the second level lateral dodging and edge-finding, this level is one-step-at-a-time, you-cover-the-front-I-cover-the-back... Tight cooperation (Alien Swarm is a co-op game), because if you dodge about you'll fall to your death.
So I guess I realized that I was switching up the styles of geometric player experience.
Final level is essentially a district level, AND a strong corner. There is no fighting here. It's a work-together level. You are loading a key payload, and you hear artillery in the distance. As you get closer, you hear it louder and louder; it shakes everything. (Actually, this I used as an experience from when I was in the army: during one battle-oriented training exercise, holding a bridge and hearing the relentlessly oncoming [simulated but still loud] artillery shells, signalling the approach of threats.) Meanwhile all around are personnel working working working... Just trying to keep the friendly Marines fed with ammo so those Marines can keep killing killing killing aliens... So there is a sense of ambient threat, but also a sense of district (an "army life" feel), and a sense of wonder - witnessing a different kind of braveness: that of the rear-area soldiers who toil toil toil...
But the final part of the last level has a strong portal: you need to blow a hole through the wall. This kind of gives "birth" to you, as you then step out to the battlefield, to join with the other Marines, about to be thrown into the frontline...
Meanwhile, the curious thing of any top-down shooter is that, in terms of vistas, you have to think *downward*. Thus, there are many catwalks and bridges and so forth. To visually foreshadow the coming level, it always has to be below you. Thus in the second level ("Mission 3"), your escape pod begins having crashed into the side of an office tower: allowing you to see, below you, in a single sweep, the entire battlefield you will need to now cross.
The edge-as-transition definition is quite true as well, but in the top-down shooter this winds up quite frequently being a bridge: you can see a vista below a bridge. The space station of the first level has this in mind as well: the vista you see - at the very beginning; what you will eventually (re)enter - is the earth itself: your home... which you are unaware, in your absence, has been overrun with the same hostile creatures you set out to fight a year ago on the offworld colonies.
Anyway, your talk was a great presentation and suddenly gave me a much clearer language of essential concepts I had been building into this campaign. You can see the trailer at the website, if you like (www.preparetodrop.com).