Self-assured and sonically restless, Charli XCX is a chameleonic pop force. This mixtape lets her middle-finger-flipping attitude loose on '80s synth-pop and it’s a cinematic experience loaded with sharp plot twists, A-list cameos, and an epic finale. The curtain rises with the Carly Rae Jepsen-starring “Backseat”’s sparse, coiled electro, and Charli sharply questions the cost of love across staccato beats on “Porsche," but “Out of My Head” is the real scene-stealer. United with Tove Lo and ALMA, the trio bid to rid themselves of a no-good lover on a shimmering pop gem. This is the sound of girl power in 2017.