Shawn Mendes is tall, dark and, um, cute. Ask an 11-year-old girl. Or her 14-year-old sister. Or maybe even a 20-year-old college student.

Mendes is the troubadour next door, the attainable dude with an acoustic guitar and songs in which he shows vulnerability but lets women have power. He's been courting tweens and teens since he was 13 posting videos online. Now, at 18, the Canadian star is headlining his first arena tour, which visited sold-out Xcel Energy Center in St. Paul on Sunday.

The Illuminate World Tour should really be titled the Camp Mendes Travels to You Tour. Sunday's concert was mostly a giant campfire singalong. He'd sing the verse of a song and then shout "c'mon, sing" and the 15,000 fans would take the chorus and pretty much the rest of the song. Never mind that his sometimes deep voice made it well nigh impossible for fans to find the right key. Just belt it out around the campfire. Enthusiasm is what counts.

You couldn't find a more enthusiastic crowd. Fans knew the words to every single song — even the cover of Ed Sheeran's "Castle on the Hill." Many carried "Happy Birthday Shawn" signs because they know that Mendes turns 19 on Tuesday.

The evening felt a bit like the first time Taylor Swift headlined an arena tour — girls, girls, girls (and their parents) everywhere, many attending their first concert. Before the concert and at intermission, they enveloped the merchandise booths 15 people deep to buy 10 different Mendes T-shirts, blankets and gym shorts emblazoned with "Shawn Mendes." There was no wait at the beer stands.

During the 95-minute concert, some of the newbies seemed more interested in watching Mendes on giant video screens even though he was standing a mere 15 yards in front of them. Guess kids just like looking at screens.

This concert was a good example of how art and popularity figure into where a show is held. On Saturday, Bruno Mars, who has had three multimillion-selling albums and been featured on seven No. 1 hits, played to a standing-room-only crowd at the X even though he's popular enough to fill stadiums. However, he doesn't think his art would translate effectively in football and baseball fields. By contrast, Mendes' popularity — he's had two No. 1 albums — screams arena, but his art croons theater.

Mendes is mostly an acoustic-strumming songsmith. Although he was backed by four older and electric musicians, he still came across like a neophyte folkie. Moreover, his modest staging didn't demand arena, what with no special effects, fancy sets or elaborate lighting. He did have an illuminated globe suspended over a satellite stage, but the globe was seldom utilized. And, before the encore, on a giant screen, he showed an enigmatic video in which he appeared to be drowning and reliving the highlights of his career. Go figure.

That was it as far as showmanship. Mendes doesn't dance. His idea of choreography is to teach the lyrics of a lesser known tune to his fans and then have them sing the words back to him. At one point, he even playfully implored the dads to sing along with their daughters.

The Toronto guitar man was just full of nice-guy sincerity in conversation and songs. Without mentioning the X or St. Paul by name, Mendes recalled playing there at KDWB's Jingle Ball in 2015 and experiencing a loud reaction from a large crowd for the first time in his nascent career. He even described a photo of him coming offstage that night, down to the green plaid shirt he was wearing.

His songs are equally earnest. With squinting sincerity, he delivered "A Little Too Much," about a woman being afraid, and "Stitches," the big single from his 2015 debut album about him feeling down after being dumped. Even the more grown-up tunes from his sophomore album, 2016's "Illuminate," such as "Bad Reputation" (about a woman's rep) and "Patience" (about him hooking up with an older woman) were rendered with heartfelt vulnerability.

Of course, Mendes could do no wrong with his audience. However, maybe by the next time he comes back to the Twin Cities, his stagecraft will live up to his popularity.

Opening the concert was piano pop star Charlie Puth, who, at 25, seemed like a polished veteran compared with Mendes. Puth talked about the back story of some of his songs, including his breakthrough hit "Marvin Gaye." The big crowd-pleaser was his Wiz Khalifa collaboration, "See You Again," which ranks as the second most watched music clip on YouTube of all time. All told, Puth's half-hour performance suggested remarkable improvement since his last Twin Cities gig at the Varsity Theater in March 2016.


Twitter: @jonbream