I finish a GTK interface with GTK3.18,and it works well,but when i change to GTK3.14 version,the interface turn out to be very bad,the size and the colore of the widgets is changed,and i find there is no enough information about the GTK3.14 version.
The CSS 'api' was basically undocumented and unstable before 3.20 so there isn't really any reasonable way to support all versions before it unless you make a separate theme for each version.
what's the difference between GTK 3.14 and 3.18 on the css load