Follow the links below to see examples of different types of mobile navigations. Download the zip files to try it yourself. Test to see if these are built using progressive enhancement techniques:
http://dan-wong.com/mobilenav/css-only/css-nav.html
http://dan-wong.com/mobilenav/css-only.zip
https://dan-wong.com/mobilenav/multitoggle/
https://dan-wong.com/mobilenav/multitoggle.zip
https://dan-wong.com/mobilenav/Respond-Menu/
https://dan-wong.com/mobilenav/Respond-Menu.zip
https://dan-wong.com/mobilenav/responsiveslideout/
https://dan-wong.com/mobilenav/responsiveslideout.zip
https://dan-wong.com/mobilenav/slideoutcss3translate/
https://dan-wong.com/mobilenav/slideoutcss3translate.zip
https://dan-wong.com/mobilenav/topdown/
https://dan-wong.com/mobilenav/topdown.zip