I have spent the weekend developing a responsive site with breakpoints at these media queries (sizes):
1200
1000
825
760
625
425
I have been unsuccessful in my attempts at getting a hamburger menu to fully work so that was frustrating but my navigation is working on all sizes after targeting the parent and children in the navigation hierarchy thus,a step forward. This is a screen shot of my progress so far in a screen of 1200 px wide:
