All around the nation this morning, Spencer's Gifts employees are in a panic, as entire inventories of mood rings go flying off the shelves.

The Legendary Miss Britney Spears' ninth studio album Glory weighs in at a robust 17 tracks as is — and yet, she was somehow still keeping one DJ Mustard-produced, ring-shaped gem up her glittery sleeves: "Mood Ring," a bonus track available solely on the Japanese edition of Glory upon its September 14 release. (For now, anyway.)

Don't let the bonus track status fool you: the song is one of the most mature, mysterious and, well, moody cuts from the Glory sessions, and is undoubtedly an album highlight.

Britney's temperature is at your command, as her voice stretches and stutters across the murky, atmospheric and #SomethingMoreUrban production, vaguely recalling another Mustard-helmed masterpiece from earlier in the year: Rihanna's "Needed Me." It's ANTIney, bitch. (There's an element of Brit's own spark-igniting "And Then We Kiss" to the song, too.)

The intimate production is lusty and vulnerable, as the "Private Show" princess seemingly strikes a cautious balance between maintaining her onstage pop star persona ("Look in the mirror / Who do I see? Who do I wanna be today? / If you came for show, which role should I take?") and letting down her emotional guard — broken hearts of the past be damned — in her personal life.

"I have no secrets / 'Cause there's a version of me that I don't know how to hide / When you're making me glow, with your fingers against my thighs," she seduces. "Gl-o-o-ow!"

“We were writing it for Britney from the beginning...we love how Britney’s gone through all her phases, and hair colors, and literally, like, mood swings. Her whole life is like a mood ring," songwriter Melanie Fontana, who co-wrote the song with Jon Asher, said in an interview with PopCrush days ago.

“We got something harder than hard,” Mustard first described the track over a year ago.

Lyrically, sonically, vocally — it's all stellar stuff from Miss Spears, and the color-changing cherry on top of an already impressive era. (Yes, Japan lucked out in a major way.)

So go ahead and start firing up those fan petitions to make this one an official single on either Britney or DJ Mustard's part — or, at the very least, to make it available beyond Japan.

"Mood Ring" is available on the Japanese edition of Glory, via CDJapan.

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