Joss Whedon uses his latest Avengers film to provide audiences with a lot of entertaining explosions '€” as well as a serious discussion about power and some bleak predictions on humanity'€™s fate.

The film begins by assembling the Avengers '€” Captain America (Chris Evans), Iron Man (Robert Downey Jr.), the Hulk (Mark Ruffalo), Black Widow (Scarlett Johansson) and Hawkeye (Jeremy Renner) '€” for a full-blown attack on a castle in Eastern Europe.

Inside, Hydra '€” a group of multi-national baddies '€” have the staff of Thor'€™s step-brother Loki '€” which, if it falls into the wrong hands, could endanger the universe.

The set piece is an eye-pleaser for any Marvel geek or superhero fan. Whedon masterfully displays each hero'€™s unique skill and power as they take on tanks, rocket launchers and a battalion of soldiers, using detailed and well-crafted CGI-powered choreography.

There'€™s also Whedon'€™s trademark witty banter that breaks the fourth wall, as Captain America warns Iron Man to watch his language because there are probably kids watching '€œthe movie'€.

Two new villains are also introduced in the fight: twin siblings Pietro '€œQuicksilver'€ Maximoff (Aaron Taylor-Johnson) and Wanda '€œScarlet Witch'€ Maximoff (Elizabeth Olsen), who let Hydra turn them into super-soldiers to pursue a vendetta against Iron Man (or his alter-ego, Tony Stark).

Pietro gets super-speed, while Wanda can manipulate objects '€” and minds, specifically that of Tony.

Eventually, Tony discovers that there'€™s a super-computer in Loki'€™s staff that he uses to make a sophisticated artificial intelligence (AI) robot named Ultron that he hopes can save humanity.

Super-heroes: Captain America (Chris Evans) and Thor (Chris Hemsworth) both return in the Avengers sequel. ©Marvel Productions

Sadly, things go wrong when Ultron (deliciously portrayed by James Spader in a motion-capture suit) decides to wipe out the human race. It breaks loose, infiltrates Tony'€™s battle robots and starts scouring the Internet for the nuclear launch codes.

Here'€™s where Whedon takes the film on an unusual tack: Amid the mad robot'€™s rampage to end the world, Captain America and Iron Man square off on ideological grounds.

Captain America, despite his red-white-and-blue uniform, has never simply represented narrow-minded nationalism. Peace without freedom is meaningless for Cap, who remembers the lessons of World War when it comes to relying on powerful states '€” or machines '€” to keep the peace.

On the other hand, Tony, who grew rich making and selling weapons, is pessimistic. He has seen first-hand the atrocities that people are capable of '€” and is comfortable with a '€œBig Brother'€ who might be able to ensure peace and order.

Ultron'€™s programming is the darkest realization of Tony'€™s ideas: The robot is a radical fascist who sees humans as absurd. It can'€™t grok why people wage wars to achieve peace '€” and so decides to wipe everyone out, starting with the Avengers.

Set piece: The film opens with the Avengers launching an assault of a Hydra-run castle. ©Marvel Productions

Kudos to Spader who gives Ultron the soul it needs as a tragic protagonist. Spader, famous for morally-ambiguous-yet-charismatic roles in series such as The Blacklist and The Practice, makes Ultron one of the most memorable villains in recent movies.

Despite the film'€™s philosophical overtones, Whedon keeps Age Of Ultron on course as a superhero movie full of high-octane action and fight scenes, which at times feel excessive and make you wish that the heavyweight cast was given more time to develop their characters.

Surprisingly, the hero who is best fleshed out is Hawkeye, who spent most of the first film brainwashed. In Age Of Ultron, the famed archer, despite his lack of superpowers, plays an important part in keeping his colleagues together after their manipulated by Wanda.

Whedon also gives time for some romance between Black Widow, the ex-assassin, with Hulk'€™s alter-ego, Bruce Banner '€” a scientist with an anger management issue.

However, Downey '€” an excellent actor famed for playing complex and internally wounded characters '€” simply was not given enough time as Tony to explore the character'€™s paranoia about the future destruction of humanity.

Thor, too, was almost invisible throughout the film. The mighty Norse god spent most of his time hamming it up as the group clown.

Whedon'€™s formula in Age Of Ultron might not appeal to everyone. His decision to embark on an epic over-the-top presentation of special effects came at the expense of character. On the other hand, the debate at the core of the film promises something more for Captain America: Civil War, scheduled for released in 2016.

In that film'€™s suspected source material '€” Marvel Comics'€™ Civil War series '€” the philosophical differences between Captain America and Iron Man boil over, pitting the two superheroes against each other.

There'€™s a lot to explore. Hopefully, Marvel can do the comics justice when adapting Civil War, one of the most significant story lines in the Marvel Universe.

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The Avengers: Age of Ultron

Director: Joss Whedon
Producer: Kevin Feige
Script: Joss Whedon
Cast: Chris Evans, Robert Downey Jr., Mark Ruffalo, Scarlett Johansson, Jeremy Renner
Cinematographer: Ben Davis
Production company: Marvel Studios
Run time: 141 minutes