Are you making anagrams by hand and have a hard time keeping track of the letters you used? This little program is here to help!
Provide a source text, start typing your anagram, and it'll tell you which characters you can and cannot use. It removes the characters you used from the source so you can see which ones are left, and it warns you when you're trying to use a character that's not in the source.
It's case-insensitive, and only cares about alphanumeric characters.