THIS is what YouTube was created for!

[user328]

Here's a very accurate one. It uses multiple images of the moon encoded as text strings in JavaScript, making it quite portable.

https://imgur.com/a/eUX3oX5

The original script was written by Graham Fairweather and released under the GPL license:

https://jsfiddle.net/Xotic750/YQqcj/

I refactored it as a JavaScript object, moved the encoded images into a separate file, and moved some Date and Math related functions to their respective built-in JavaScript objects.

How to use it:

https://pastebin.com/Mzu8d1RA