It contains 50 original levels and the 40 from Extra.
(Total is 90 levels)
Level data is from
http://www.sourcecode.se/sokoban/levels
As far as I know the originals and extra levels are public domain.
So All Level is opened free.
Download and Enjoy game!
Thanks.
Direct Link to GooglePlay :
https://play.google.com/store/apps/details?id=com.duckinthedarkhole.socoban