- Will the ground tiles be "known" to the procedural generation scripts? (so that grass is not placed on concrete etc.?)
Yes. That is already the case, which is why you don't see trees on the road or grass on the skyscraper. But grass going over concrete is desirable, as this is a post-apocalyptic setting.
Will there be multiple layers of "things" possible to be generate by the scripts? (Base layer = Terrain | Layer 1 -> Dirt/rocks/Tinting of Base layer -> Layer 2 - Plants small -> Layer 3 -> plants large ?
Yes, that's also already evident in the screenshots and video, actually. We don't at the moment provide tinting control (as diffuse colorization doesn't look super great for this sort of thing), but the rest is featured already in what you're looking at.
What about terrain shading? Tile based approach only allows terrain shading if you blend shading elements over them before applying the plants, so its important procedural generation can be done in layers and stages....
Nope, not supported, not likely to be. The ground layers can be large and repeated, as can other elements, though. The tile system is 64px square, but a lot of the actual textures used are other larger powers of two. Those in turn can be tiled one direction or more. And in terms of the grasses, etc, they can obviously have smaller elements that are individually animated (as you see).
None of that stuff will be player-definable in scripts, though. We'll provide the types of tiles, and players choose from them. The best scripts will actually support many random different sets of tiles, rather than one specific look, but that depends on the type of script, certainly. The idea is guided randomization, rather than a jillion hand-crafted designs. Though the hand-crafted non-random designs are also possible.
Anyway, if there are player suggestions about types of tiles, or new behaviors for tiles, or even art submissions, in alpha and after we'll definitely take those into consideration, but we'll have to do the implementing and they'll have to fit with the overall art aesthetic, etc. But that sort of thing is pretty quick for us to implement in code, and if it's just new art you can replace existing assets with your custom ones to test them out, same as with AI War.
- Light and Shadows? Yes, no, Maybe? 
This is a 2D game, so definitely no real shadows. We
may support having blob-type shadows for a few things, but not even sure we're going to go there. It won't be a focus for alpha, though. I think it would possibly clash with the art style since it would only work for certain types of objects anyway, but we'll see.
In terms of lighting, we are planning on supporting lighting in dark places. So, for instance, inside caves or whatever, having the player emit a weak light source, and other things like candles, lamps, etc, emitting stronger light. That won't be player customizable, though, as we'll have to wire up the behaviors of any new objects, and in general players can't directly add new objects or functionality: just new compound object designs, basically, using the building blocks we provide. But, of course, we'll be open to suggestion and submissions of art and whatnot, time permitting.
During alpha (and especially before) we're going to be pretty crazed just trying to get all the functionality we want in there, and so we won't be implementing a lot of feature suggestions due to not wanting the schedule to get off track -- some suggestions, just not a lot of them. Then during beta, we'll be doing a whole heck of a lot more content implementation, and in general trying to focus on polish, new building blocks, new scripts, new art, etc, etc, etc. Even moreso than in alpha and pre-alpha. So during that time we'll be particularly receptive to suggestions and submissions, though we'll welcome having them prior to that, too.
With all 3 elements being interlinked in 1 procedural chunk (so that that element can be procedurally spawned according to certain rules but always in the same "layout" ?
It's actually pretty cool, there's a lot of layering you can do, and multiple randomization methods you can use to accomplish them. It's hard to explain without getting to in depth, but we'll be showing examples of the results through screenshots every week between now and alpha, and beyond. It's a pretty flexible system, but there are certain limitations that I'd rather not get into just yet. Mainly that it's difficult to handle transitions between different ground types inside a single chunk, and so most of the time it's going to be a matter of plants and objects seeded on top of that ground providing the variance, rather than doing anything particularly fancy with the ground (dirt, etc) itself. It will be easier to show you some of what's possible as we get more content in the game, but the screenshots so far are a pretty good rough guide there.
My idea would be to simply have a base underground and then apply shading in the first procedural pass - this shading is then applied to all the procedural elements that are placed above if we set it do that so that a grey rock placed in blue shading produces a slightly blue rock etc....
That sort of thing won't really be possible at all, unforunately. Instead you could have something like a grey rock layer, and then a layer of partially-transparent mud perhaps, and then a layer of road over part of it, and then different kinds of grasses on top of all of the above, and then some water over near the mud, with reeds by the water... all sorts of things like that. But it's all geared about combining multiple sprites and layers, rather than having any shader capabilities whatsoever.
We want this to run on a toaster, is part of it, but also that sort of visual styling just isn't the focus on the game. We're here to create lots of unique and interesting places, and the art is in service to that, but the art itself isn't intended to be a showpiece like Crysis or something.
