it should work, did you put the css between <style> tags?

also the box-shadow is a box shadow, you might wanna change it to text-shadow if that's what you'd expect from it

text-shadow works. Was the use of box shadow a mistake?

that snippet of code was never meant to be used, it was supposed to be illustrative code that fits in a tweet

text-shadow does make more sense if you're actually trying out the code, but the original intention was to demonstrate a more complex element having a shadow modifier