Theme: 21, for no apparent reason.
I figured it was time that I started posting puzzles instead of merely reviewing other peoples' puzzle apps or showing how region parity worked.
Because I create these puzzles in Paint.NET instead of using a script to do it like most puzzle authors (I do not have the programming knowledge necessary to write my own script, and I'm really not sure if anyone wants to lend me theirs), these puzzles are of a very low resolution. On the other hand, this means that I don't have to carry around with me a notebook for keeping track of my puzzles; I can instead carry around with me a notebook for keeping track of my puzzles, something which I already do. (Let the meaning of that previous sentence sink in.)
It's a slight shame that it's not my 21st birthday, or that of anyone whom I know. Perhaps I should have waited until it was to post this.
As with pretty much every other puzzle blog on the rest of the internet, DO NOT SPOIL THE ANSWER IN THE COMMENT SECTION. If you absolutely must spoil something regarding the puzzle-solving process, please encode it with ROT13. Should you require assistance with the puzzle, you may email me at the email given in the "About" page.
As with pretty much every other puzzle blog on the rest of the internet, UNIQUENESS LOGIC AND PURE GUESSING ARE FAIR GAME. However, in either case, you will not get as much satisfaction from solving the puzzle, and in the latter, you have not proven uniqueness of the solution, which is something which I somewhat frown upon for most puzzle types.
Finally, should you find multiple solutions to a puzzle, it is best posted as a comment instead of an email.
So in other words, please obey the rules of every other puzzle blog on the internet.