When you click on "full screen mode" button ms-fullscreenmode class is added to the <Body> tag:
Solution:
A sample snippet of CSS that will hide your controls in full screen
/*hide controlID div only when full screen mode is enabled/
.ms-fullscreenmode #controlID {
display:none;
}
#controlID - id of an HTML element that should be hidden when "full screen" is clicked
#controlID - id of an HTML element that should be hidden when "full screen" is clicked