The Marvel Cinematic Universe now shows no signs of diminished returns. Doctor Strange made well over $600 million, while Captain America: Civil War was the biggest blockbuster hit of last year. They're going nowhere, and they're at the peak of their powers. But they are becoming denser and harder to follow if you're not willing to invest in every thread. It can pay off massively for the dedicated, but down the line it's only going to become more complicated. It's arguably already too complicated if you're coming at these films for the first time - and there's not loads more space for extra characters to join the fray.

For me, Captain America: Civil War is the peak of the Marvel Cinematic Universe to date. It takes advantage of having 12 preceding movies to draw from in creating tension between its characters, as well as going deeper into their relationships. You don't typically get to spend long enough with characters in blockbuster movies to get to see their friendships slowly disintegrate, like in the case of Steve Rogers and Tony Stark. Civil War is also extremely busy in terms of the number of characters in the mix, and has to work hard to give every hero their moment across its sizeable 147 minutes running time.

They just about manage it. But if that was your first Marvel movie, it’s tough to tell exactly what the hell was going on. It's a film about men and women in capes who get bollocked by the UN for causing mega disasters across the globe, you're told, who then have a big fight in Leipzig airport. It's not exactly accessible anymore - not in the way that the first Avengers was in 2012, where the characters' backgrounds were a bonus but not essential to really understanding. Being borderline impenetrable is not a problem if Marvel is happy to continue preaching to the converted, like me, but with 14 films in the can, I wonder what their plan is to keep the story growing without baffling anyone who doesn't want to watch that many DVDs to follow it all.

(Image credit: Marvel)

In theory, 2018's Avengers: Infinity War will be even busier, bringing Captain Marvel, the Guardians, Doctor Strange, Thor, Hulk, and Thanos into the equation. Is there such a thing as having too many toys to play with? It's not like these films are dense, complicated ensemble thrillers, after all - they are popcorn movies where living action figures punch each other. But accessibility is a problem that superhero comics have similarly tackled as they've accumulated decades of continuity, as well as heaps of supporting characters. At some point, it becomes overwhelming to those looking to become new fans, and a bit of a reset is necessary.

The MCU is not quite the same deal as its source material. For one, they've tried to combat getting too continuity-heavy by deliberately adding more solo movies like Doctor Strange or tonally distinctive pictures like Guardians of the Galaxy, that deliberately peel back more layers of this fiction they're building, adding mystical and sci-fi elements respectively. That has its drawbacks, too: Guardians aside, the origin films have a bit of a rigid formula. But it does mean the audience just needs one character as a way into the larger, Avengers-heavy movies - even if they don't understand all of what's going on.

Something to keep in mind: a 10-year-old kid seeing Avengers: Infinity War in 2018 will have been born the year Robert Downey Jr first became Iron Man. They are the main audience for these films. These have to make sense to them, in much the same way that Star Wars picks up a new generation with the start of every new trilogy, or even from watching a TV series like The Clone Wars. With every new Avengers team-up or solo movie, the universe gets a little less easy to keep track of to someone trying to pick it up for the first time.

(Image credit: Marvel)

It's likely that Marvel has already thought about ways to combat this. Some kind of reset will follow the fourth Avengers movie due in 2019. “In some respects, they’re going to be the end of some things and the beginnings of certain things,” co-director Anthony Russo told the Independent . It sounds like the ideal jumping off point for some long-time characters or actors - it's possible that at least one actor from the original Avengers line-up will want out from their superhero role by then.

If the original Avengers line-up breaks up, it's not a big deal. It might actually make these films easier to follow again. Maybe there can be a new line-up of Avengers, without the same history and backstories - maybe there can be less characters again. Civil War still feels like it's nearing critical mass for how many of these heroes you can have on-screen without utterly confusing the audience. Infinity War, then, will be an interesting test, as the Guardians, Avengers, and Doctor Strange all converge. How will that not be confusing if it's your first Avengers movie?

Continuity can be both rewarding and a crutch. For the converted, the biggest moments of the MCU can be tremendous, unusually impactful viewing, like a season finale to a great TV show - it's really not the same as watching a traditional trilogy of movies. The payoff can be a lot bigger. To new viewers, though, watching the season finale isn't much use without watching the rest of the show first.