It's amazing how little time it took for the Berkeley-based pop-punk band Green Day to plummet from godzillion-selling superstardom to the point where folks are muttering the word "has-been." Like Hootie & The Blowfish, the transformation happened without the group doing anything to alter its style; 1995's Insomniac, which began the downward spiral, was basically a thinly disguised remake of the previous year's breakthrough Dookie. As a probable reaction to the backlash, the new 18-song Nimrod takes the opposite approach: Instead of sticking to a tried-and-true, guitar/bass/drums punk-pop blueprint, Green Day tries every possible variation on its sneering, pop-minded ways. That means you get speedy, profanity-laden punk ("Platypus (I Hate You)"), a low-key surf-rock instrumental ("Last Ride In"), and even, God help us, an acoustic ballad ("Good Riddance (Time Of Your Life)"), which, if all goes according to plan, will be on every radio station in America every five minutes for the next six months. As has been widely publicized, stabs at maturity are peppered throughout Nimrod, from the aforementioned ballad and instrumental to the presence of horns and strings on a number of tracks; there's even a harmonica on "Walking Alone." But, as you can imagine, this is still a Green Day record all the way: Songs like "Jinx" are full of self-deprecating lyrics like, "I fucked up again / It's all my fault." If Green Day still has a loyal following, its fans are bound to find something to like on Nimrod; for all the attempts at diversity, the record is packed with mile-wide hooks and sing-along anthems. Now, it'll be fascinating to see whether anyone buys it or not.