Does not work properly when a negative number is given

You could also do (0...number) instead of (1...number)

Interesting! I was not aware of the range syntax with 3 dots, where 1...n exludes the end of the range.

that validation was brilliant!

O my love. So beautiful

short and pithy，easy to read

https://github.com/bbatsov/ruby-style-guide#sprintf
http://ruby-doc.org/core-2.3.0/Kernel.html#method-i-format

The satisfaction when you submit code that resembles the best ranked solution. \m/

THank you! But what do you call this sort of operation? - "%.2X%.2X%.2X" % [arr]- I'm looking for a key term to google so I can learn more about how to use this tool, and how it works. Is it shorthand for something else?

This is how it's broken down:
First, look at the two BIG pieces: "String Format" % what_to_format (takes array as input)
So, left side is saying, "format as hexidecimal", right side is saying...
"take r,g,b array, and "map" it. What map does is take each element, and transform it somehow. How? you tell it how in the function that you pass it. The function he's passing is taking the r,g,b numbers and ensuring that they are between 0 and 255. if they're not, it forces them into that range.

So in the end it looks something like this "%.2X%.2X%.2X" % [27,255,133] (or whatever rgb values it is)