jQueryUI upgrade from 1.10.4 to 1.11.4

jQueryUI upgrade from 1.10.4 to 1.11.4

I am upgrading jQueryUI  from 1.10.4 to 1.11.4. In 1.10.4 there is "base" theme folder. But I am unable to locate similar theme in jQueryUI- 1.11.4.

What is the equivalent on "Base" theme of jquery-ui-1.10.4 in jquery-ui-1.11.4 ?