yes it's a 1px shadow with black color in 90º, this technique it's a lot used even on text and it gives the feeling of embossed shape. You can use it as normal with some transparency or on overlay or softlay : )
About shadow I know very well XD (No rly, that's just missunderstanding XD). I mean, those little thingies. They are very cute, but I never thought about them! Those things - are georgeous! XD Thought, I'll use them in future. I see most greatest using - as dividers between menu buttons or content dividers. And yeah, afte comment I noticed, that they are 1px big both dots XD
Bassicaly - yes. But those geometrical manipulations were quite simmple. If test every function and remmember, how it work, you can acces some interesting effects. I hate only one thing - those mannipulations are so hard to make work them on each other. Every time you try to add something, vertices just dissapear, cuz of incorrect effect.
You musdt think in 3dspace by 2d platforms. Those triangles - youwill notice, that theyre points change theyre 2d platform layout in 3d space. By that you can do even powerfull images, which I just don't want to do (too lazy and no such a need).