Functions
unit(30px / 5px) #=> 6
unit(5, px) #=> 5px
e("ms:stuff()") #=> ms:stuff() (unquote)
%("count: %d", 1+2) #=> "count: 3"
iscolor(@x)
isstring(@x)
isnumber(@x)
iskeyword(@x)
isurl(url(...))
ispixel()
isem()
ispercentage()
isunit()
hue(@color)
saturation(@color)
lightness(@color)
luma(@color)
luminance(@color)
fade(@color, amount)
fadein(@color, amount)
fadeout(@color, amount)
spin(@color, degrees)
mix(@a, @b, amount)
Conditionals
.image when (luma(@color) > 50%) { }
.image when (not(...)) { }
.image when (default()) {}
.image when (e(@shape) = 'circle') { }