[yugecin]

Asking the OS and screen size seemed a logical question at the time, but indeed it shouldn't really influence the result. The OS might be important if at some point I'd want to create a native app (but that's more like an argument to justify my questions rather than a valid reason). Actually I'm a bit wondering why I didn't ask myself the question if it would be necessary to know these parameters.
And about the windows phone OS - I totally forgot to add it to the options, no real reason why it's not there.

Anyhow, thanks everyone so far for the responses.