i saw something like this project of yours some time ago in MSDN News (**broken link removed**), well, i will only give you some ideas...
To use on the floor grid squares try using 5mm (at least, and depending on the area) sheets of translucid Nylon (
Nylon - Wikipedia, the free encyclopedia) of any type (Nylon) or you may also consider using Polymethyl Methacrylate (Plastic Type) (
Acrylic glass - Wikipedia, the free encyclopedia), keep in mind that if you leave no room below theese sheets their integrity will be enhanced by the floor structure itself !
I would recommend that you use both, Nylatron as the top and most abrasive resistant layer and the Polymethyl Methacrylate layer below (to provide light expansion) with the LEDs mounted on. (Beware of broken legs with Nylatron, use an less lubrificated Nylon if no broken legs are required !)
As the grid support you could use cheap Aluminium tubes or if your budget is really tight, use wood bars...
For the electronics part, you could use the Serial Port with and TTL 8Bit common Shift Register and an RS-232 level converter like the MAX232... (or an FTDI232 chip to provide USB to Serial)
For the software side use Visual Studio .Net (i personally use C#,... C++) try Basic if you have no programming experiênce... .Net offers an easy SerialPort interface component, very easy to use, just drag and click it on the IDE (visual studio) to apply some code to the event...
The Shift-Registers also allow you to build an chain of modules and i guess this way you can choose how mutch you can spend
, also instead of the MAX232, since you only need the Tx of the SerialPort you could use an simple transistor and 2 resistors to pulldown a little the 10volts that came from the RS-232.
Well, i hope i've have given some ideas to you !
Try not to burn down the house !