Homepage is now the all white with black text template and won't let me edit any of the sections.

I was trying to add a few custom css elements to my homepage like, having the hamburger menu display on desktop, adding a block behind the navigation bar when you scroll, etc. Upon adding this code I noticed that my homepage has now turned to the White with Black text style and won't let me edit it. Also I had certain shapes that were added to the page in black and those shapes are now transparent. Additionally, something messed with the footer as well which is now white with black text. The footer is different and correct on all my other pages. I removed the custom css elements that were added tonight and the issue is still showing. 

APEX Specialty Vehicles - Custom Mobile Vehicle Manufacturer (squarespace.com)

Could it be that your HTML is invalid after you added your code? A tag that has not been closed properly can cause CSS to mess with your styles.