Your parent theme twenty-twelve is a mobile first layout (styles are declared for small-screen view and as media queries deal with larger screens). Your child them Revision Courses is desktop first (styles declared for big-screen view and media queries deal with smaller screens).
So Twenty-twelve has styles kicking in once it is bigger than 600px and the child theme has different styles kicking in once its smaller than 770px. All the style changes that are happening at 600px (@media screen and (min-width: 600px)
) in twenty-twelve need to be redeclared in your child theme’s style and kind of undone by declaring the values those menu elements had before the @media screen and (min-width: 600px)
. An example would be parent theme’s style @media screen and (min-width:600px){ .main-navigation li a{ display: inline-block; ...}}
needs to be declared and changed in child them @media screen and (min-width:600px){ .main-navigation li a{ display:block;...} }
Once you’ve undone the style changes the parent theme was adding at min-width:600x;
you need to re-declare them where you want e.g. @media screen and (min-width:725px){ .main-navigation li a{ display:inline-block;...} }
Best keep to child themes that are mobile first if the parent theme is.