There were a lot of things that made me sit up and say, “Hey now!” with last year’s Across the Universe, but the one that sticks with me still was getting a wonderful shiver running up my back watching its young unknown leading man, Jim Sturgess, and knowing, absolutely knowing, that I was seeing a future major star in the making. That movie didn’t do it for him, and this one might not either, but his day is coming — mark my words. Sturgess (who has a small part in The Other Boleyn Girl, too) is the best reason to check out 21, which is almost entirely preposterous — never mind that it’s apparently based on a true story — and yet somehow wonderfully entertaining at the same time. That’s mostly due to Sturgess: his Ben Campbell, poor MIT undergrad desperate to raise 300 grand for Harvard Med, gets entangled with a gang of whiz-kid card counters who make regular killings at Vegas blackjack tables. Need I tell you they are responsible for sweetly geeky Ben metamorphosing into a slick monster? The mechanics of how they run their scam are fascinating, but the sheer dumb implausibility of how they utterly fail to shield themselves from watchful casino eyes — even to the point of returning to the same casino over and over again — beggar belief. Oh, and I forgot to mention Kevin Spacey, here as the mathematics prof Fagin to his quasi criminal student card sharps. That’s how good Sturgess is: he steals the movie from a regular movie thief like Spacey.