“Lucy” is exactly what you would expect from a Luc Besson movie: it moves like a bullet, and almost never stops to take a deep breath (hence the short running time). This is beneficial, because the story doesn’t always make sense…but when a film is this energetic and entertaining, it would be a shame to spoil the fun by demanding too much of it. Scarlett Johansson is well cast as a student in Taiwan who gets tricked into becoming a drug moll for a weirdo called Mr. Jang (Choi Min Sik). But when the drug implanted into her intestines leaks, Lucy turns into a superbrain, capable of anything you can think of. Writer/director Luc Besson has crafted a fairly unbelievable story, even though its central idea of “accessing 100 percent of your brain” is quite intriguing. I’m afraid I saw his climactic “reveal” coming almost a mile away, but he has filled his movie with colorful details and some solid action scenes. The result is a movie that’s diverting and genuinely exciting to watch. I wish its story were air-tight, but even with its flaws it provides solid summer entertainment and a good showcase for its star. Whether you buy it or not, hang on for the ride.