If you know anything about Edge of Tomorrow, you know that it's Groundhog Day meets Battle: Los Angeles (you know, if Battle: Los Angeles had been good): Tom Cruise fights aliens, dies on his first day of battle, and wakes up the morning before to repeat the experience. Anyone who's played a video game (and the film is certainly evocative of one, with its soldiers clanking around in multi-weapon mech suits) will immediately realize how cleverly the premise evokes the experience: Cruise's William Cage can try anything, die in the process, and reboot. There's no further save point, but at the very least he can learn from his experience.

The premise seems annoyingly cute on paper (not helped by the "Live. Die. Repeat." advertising) but director Doug Liman and writers Christopher McQuarrie and Jez and John-Henry Butterworth quickly know how much fun they can have with it. Cage is a PR tool for the military in its losing war with the squid-like "Mimic" aliens who have already conquered Europe, but at the beginning of the film he's dropped into the front lines after resisting orders to do so. The first go-round introduces his bullish sergeant (a scenery-chewing Bill Paxton) and fellow squaddie meatheads, and from afar we hear of the heroic exploits of Rita Vrataski (Emily Blunt). Then they're dropped into battle and everything goes horribly wrong.

Liman makes you feel the carnage of the battle and Cage's utter inexperience, even though anyone who's seen any advertising for this film knows it'll end with him dying and resetting. He hasn't had a hit in years, but Liman has always been a dynamic director, particularly when it comes to action—Go had the verve of a film with ten times the budget, he set up the visual motifs Paul Greengrass expanded on in the Bourne films, and he even did his best to liven up the terminally flat Mr. and Mrs. Smith.

The lived-in mech suits recall Edge of Tomorrow's Japanese origins—the film was based on a Japanese 'light novel,' an illustrated book aimed at teens—and the "Mimic" aliens are wonderfully designed. Liman's team understands that if you're going to create creatures from pure CG, don't just make them look like animated puppets. The Mimics are a roaring mass of tentacles and flashing lights, vibrating with each step and whirling around the screen whenever they attack. They're a genuinely baffling threat.

But the film really comes into its own once Cage starts resetting. Then he can meet Rita, who he encounters on the battlefield and eventually realizes once shared his affliction. He can beef up his action credentials, of course, experiencing the same battles over and over again and training alongside Rita mercilessly for what we can only assume is a countless amount of days. Edge quickly starts jumping forward, making the safe call that the audience gets what's going on. We don't need to see Cage re-start every day, and eventually our perspective shifts to Rita, who's a little surprised but quickly on the ball for every new day, as the extent of Cage's experiences become too vast for us to comprehend.

Blunt is by far the best screen partner Cruise has had since the mid-90s. Clomping around in her skull helmet with her giant Final Fantasy sword, which she uses to swipe down Mimics acrobatically, Blunt fully sells Rita's battle-hardiness just with her eyes. She's usually cast as a tough cookie, but Rita manages to fill so many roles at once as Cage approaches her differently with every reset. First, she's the explainer, telling the audience just how this is happening to Cage. Then she's the drill sergeant, then she's Cage's able partner on the battlefield, and finally she's something approaching a friend, although she always has the distance of someone who's meeting him for the first time, even though she understands that he's spent hundreds or thousands of days with her.

Cruise is just jacked in to his traditional movie-star persona. Cage doesn't need to have much of a personality, especially since it's going to get built on so much over the course of the movie, but Cruise just needs to twinkle his eyes sometimes and look weary at others. It's a role several stars probably could have done solid work with, but that's not to discount Cruise's natural powers, which are as present as ever, even as he struggles to reclaim his old status as a Hollywood hit factory.

Edge of Tomorrow is the perfect mix of blustering action and sci-fi thinky nonsense that is best enjoyed without picking at it too much. Like so many a CGI-powered affair, it loses some steam at the end as it tries to top its epic beginnings, but it comes in at under two hours and doesn't really have time to wear out its welcome. Best of all, this is a monstrously expensive sci-fi epic that has no real consideration towards becoming a franchise or setting something else up through Easter eggs and post-credit stingers. It's worth seeing just for the performances, the set-pieces, and the strong exploitation of its high-concept premise. It's what summer movies are supposed to be for.