[Lio]

I was under the impression this project also depends on CSS variables.

If your target browser can't support CSS Grid it's probably too old to support CSS Variables (CSSS custom properties) anyway.

[extra88]

Chrome, Firefox, and Safari added support for the current CSS Grid syntax in March 2017. CSS Variable support is older. Chrome and Safari have supported CSS Variables since March 2016, Firefox since July 2014. Edge only added support (with bugs) this year and of course IE11 will never support them. Older devices that can't upgrade to iOS 10 or later, like the iPhone 4S, can use CSS Variables.

http://caniuse.com/#feat=css-variables