Logitech K830 HTPC keyboard

I recently got a Logitech K830 HTPC keyboard. Have not got a lot of time to play with it but here are some quick observations:

+ just WORKS with Linux (Kodibuntu = Lubuntu 14.04)*
+ Illuminated keyboard **
+ mouse pad on the keyboard
+ mouse pad recognises multi-finger gestures on Linux
+ well made: sturdy, and slim
+ unifying remote
- no indicator for Num/Caps lock
- non-replaceable battery

Has anyone tried to open it up and see what kind of battery it uses? From experience of using other mouse with unifying remotes, I expect it to last a long time between charges.

One thing that I can't understand is the illumination of multi-function buttons. One the product page, Logitech show the red/orange text illumniated (see image below) but mine does not. Is it a software function?

PS: this keyboard is a huge improvement in quality over the k360 graffiti family.

* - official specs on Logitech site do not list Linux as a supported operating system. Custom keys might not work, but the rest functions perfectly.