// Setting the default `rem` to be equal to the 10px, so everything based on it would be decimal
rem_px ?= 10px

// Calculate the desired font-size in `em`, so it would be equal to the desired rem_px
$page_rem ?= unit(round(16px/rem_px,3),em)

// Set the `rem` variable, with fallback in IE
rem ?= 1rem
rem = rem_px if ie