Saturday marks National Punctuation Day, the 13th observance of the holiday since it was beatified by Chase’s Calendar of Events in 2004. To anyone who sees this holiday as superfluous, I would direct you to New Yorker grammarian-in-chief Louis Menand, who once wrote that, “For any true stickler, you see, the sight of the plural word ‘Book’s’ with an apostrophe in it will trigger a ghastly private emotional process similar to the stages of bereavement, though greatly accelerated.”
To celebrate the occasion, TIME put together the following interactive challenge: Restore the apostrophes to the following two sentences. To play, click the space between or after letters to insert an apostrophe. If you change your mind, just click the apostrophe to remove it.