Written by guest contributor Dave Fox

Over the next few weeks, I’ll be counting down my top 5 films of 2015. Here's #4, Alex Garland's smart and stylish psychological sci-fi thriller.

Quick, see how many genuinely intelligent recent sci-fi films you can name. How many did you get? 10, 11, 12? Less? Four or five? Wracking my brains, I can only get enough to count on one hand. There are plenty of films categorised as sci-fi, but there are there enough that use the genre for its intended purpose: to ask questions, to make us think, to use the fantastic to look and where we are now, and where we're going. Personally, I blame Star Wars, for turning sci-fi into shorthand for "action films in space".

The good news is that films that but the "sci" in sci-fi are making a comeback. Christopher Nolan's Interstellar (2012) brought theoretical physics alongside blackhole related flights of fancy, while Ridley Scott's The Martian (another film from this year) was based on a novel that did not shy away from using - and explaining - hard science. Ex Machina, the directorial debut of 28 Days Later scribe Alex Garland (who also wrote the script) also belongs in this group. It has fantastical elements but feels grounded, and will leave your head spinning with ideas.

The film is heavier on ideas than plot. Caleb (Domhall Gleeson) is a talented young computer programmer for search engine giant Blue Book. He gets the opportunity of a lifetime when he is invited to meet his company's reclusive genius CEO Nathan (Oscar Isaac) and participate in an experiment with a groundbreaking AI (Alicia Vikander).

Ex Machina is quick out of the blocks; we see Caleb get chosen via random lottery to go visit Nathan's secluded, state-of-the-art home (that resembles a bunker more than a mansion) in the first few minutes, and the entire film then takes place on those grounds. Gleeson's Caleb is nervous, eager to please, deferential and almost apologetic about his intelligence. It's a smart, subtle performance, but scenes are frequently stolen by his sparring partner Isaac, who's unrecognisable, hiding behind bulk and a hipster beard. On the surface Nathan is pally and unusually down to earth for a reclusive, genius billionaire, but Isaac's performance hints and the reservoirs of anger beneath a placid surface.

Caleb is there to do a Turning test on Nathan's revolutionary invention, a robot named Ava. Nathan believes he may have created artificial intelligence, and wants Caleb to confirm either way by engaging in daily conversations with Ava for a week. What both men find as the week goes on is that it's not so easy to define consciousness. It's worth a mention that Vikander more than holds her own opposite Gleeson and Isaac as Ava. Her robotic exo-skeleton is a gorgeous special effect but means that her performance is mostly unspoken - she does most of her talking through smiles, frowns and her eyes, which shimmer with so much life that, really, no AI test should be needed.

Every conversation that Caleb has with Ava brings new questions. Is Ava making sarcastic jokes, or just repeating lines? Ava flirts with Caleb - is she doing it because she likes him, because she's programmed to, or is she just using Caleb to serve her own ends? Ava wants to know what will happen to her once the test is over. Caleb responds that it's not up to him, and Ava shoots back: "why is it up to anyone?".

That's what Ex Machina brings to the table. It brings questions that have no easy answers. The script could have come from Isaac Asimov or Phillip K. Dick, yet it's not derivative. Just when you think you have a handle on what's going to happen, the rug is pulled from under you. It shares DNA with sci-fi greats, but stands on its own two feet as an original piece of work. It's beautifully shot, and understands that action scenes and explosions aren't needed to hold an audience's attention.

If you're at all interested in sci-fi that explores difficult questions, trusts the viewer's intelligence and does not provide easy answers, then Ex Machina is for you. It's one of the best films of the year, and would be one of the best of any year.

Score: 4/5

Ex Machina Director: Alex Garland Writer: Alex Garland Studio: DNA Films, Film4 Running Time: 108 Minutes Release Date: 1/21/15