If you've been keeping up with your Swapnote mailbox on 3DS, you can download an update today and enjoy some new features, including the ability to take photos or record audio and attach it to your notes, undo drawings, and use different colors on each page of a note.
Even if, like me, you haven't checked Swapnote in a few months and get kind of sick to your stomach at the thought of the thousands of unread notes building up in your inbox, the update will be of interest. You can delete multiple notes simultaneously now, and filter your messages by sender.