Pretty Little Liars, the crown jewel of the Freeform network (previously ABC Family), will drop its final ridiculous surprises soon. The show, improbably sustained for 160 episodes on the basic conceit of “a group of friends is terrorized by text messages from an anonymous villain,” is premiering the second half of its final season tonight. The series finale is coming this summer — timed to coincide with the same dangerous period of adolescent malaise that instigated the violent pilot episode events seven years ago.

A number of cultural movements can be traced back to this show — dozens of nail-polish and hair-styling trends, but also the rebirth of prime-time soap operas, and the practice of TV stars live-tweeting alongside viewers. The ever-growing roster of moody, violent dramas aimed at women also likely has some roots in the PLL phenomenon. And plenty of viewers have drawn lines from Rosewood to Riverdale, or between Freeform’s pretty-girl criminals and the vigilante duo of MTV’s Sweet / Vicious. Pretty Little Liars was inspired by Sara Shephard’s genre page-turner of the same name, and the wildly successful adaptation may explain why studios have snapped up the rights to anything and everything by Gillian Flynn and Liane Moriarty. Three seasons in, The Atlantic even credited Pretty Little Liars with reinventing the slasher for TV. Scream Queens creator Ryan Murphy might owe PLL creator I. Marlene King a curt nod for that.

But Pretty Little Liars’ greatest feat isn’t its jaw-dropping ratings, which it ultimately failed to maintain, or its spiderweb of a plot, filled with specifics you can generally ignore. Each half-season piles on details, all of which seem significant, then lets the vast majority of them fall away in the wake of a plot-upending act of violence or betrayal. The show isn’t even about its character work, which careens between stereotypes and ludicrous continuity errors from season to season. The thing Pretty Little Liars addresses best is smartphones.

The way PLL depicts texting has varied widely over the course of its run. Early seasons often showed wide shots of the girls in a semi-circle, looking down at screens that weren’t visible, and reading the messages aloud in unison. Middle seasons mostly showed close-ups of the messages, letting viewers read for themselves before the Liars delivered a clutch reaction shot. Later seasons toyed with the idea of text superimposed over the characters’ scenery. Texts are forwarded, screenshotted, or typed slowly and deliberately as cliffhangers. They’re integral to the action because it’s primarily in texts from the mysterious “A” (and dozens of “A” cronies) that the girls are told where to go, what to fight about, and who to fear. Without these texts, there is no story. So it doesn’t totally matter how they’re presented, but the experimentation makes it obvious that the creative team wasn’t content to start making a show in 2010 and pin their aesthetics there.

Texting was central to PLL, and the show morphed as the technology changed. By the time the second batch of season 6 episodes debuted in November 2015 (the two-part seasons are just one of the hundreds of ways this show can be deeply confusing), the main characters had programmed responses that survived even a five-year jump into the future from the end of season 6A. They still seize when their phones go off in unison, or lurch backward when a blocked caller ID appears on their screens — now with the added stomach-drop of a smartwatch vibrating against a wrist bone at the same time.

The Liars — a foursome of misunderstood Mean Girls — went through dozens of phones over the course of their interminable high school careers, and The Verge’s tech reporters helped me pluck out and identify them one by one last September. As teenagers traded in their Motorola Bravos for the iPhone 4S in 2012, so did the group’s trendsetter, Hanna Marin, and when young adults briefly entertained the possibilities of an Apple Watch in 2016, so did the group’s type-A brainiac, Spencer Hastings. For the most part, everyone charts the same course from weird keyboard-based devices (Palm Pixi, Microsoft Kin One, HTC HD2) to the Samsung vs. Apple dichotomy dividing high schools today.

There are funny mix-ups along the way when it comes to the hardware — a stray incorrect iOS version, fake interfaces, one Nokia N8 that Spencer’s boyfriend clings to deep into 2014 — but the way technology plays into the characters’ lives is spot-on from the jump, and it gets consistently smarter and more unnerving as the show reaches for weirder and more complicated ways to scare its superhumanly resilient heroines.

When we catalogued the series’s phones last fall, I wrote, “Life happens on screens, and one of the weirdest, best things the show has done is demonstrate how the seemingly benign gadgets that are meant to make our lives better can be twisted into powerful instruments of torture.” Revisiting it, I’d say the show does one better: it highlights how we’ve gotten to the point where a cellphone is more than a tool. It’s an object you have a pretty intense relationship with, silly as that sounds.

As the years of torment march on, Pretty Little Liars’ four central girls gradually slide away from colorful, sticker-covered, differentiated and personalized phones. Instead, they acquire black or white iPhones. In part, that’s thanks to the homogenization of the smartphone, but as the characters mature, they also lose their love of zany cases and lock screens. As teenagers, they see technology as a fun, customizable pastime that mediates friendships and flirtations. Gradually, they come to interpret it as a chaotic, unknowable thing they’re linked to inexorably. Despite endless horrors, they have to keep in touch. They can’t just log off, but being logged on definitely isn’t fun anymore.

It’s a handy plot device, answering the question that plagues and nearly ruins similar melodramas like Grey’s Anatomy or Desperate Housewives. Why don’t the characters just leave this weird, inexplicably cursed place? Their reliance on the thing that haunts them is emblematic of what the show has to do to exist: it crafts a nightmare that’s persistent and believable enough to justify 160 hours of prime-time TV. And it represents what the show is trying to do to matter: build a one-of-a-kind horror story that jots down a whole generation’s experience amid its melodrama.

Building off the success of Gossip Girl, Pretty Little Liars is all about secrets, and the anonymous evildoers who threaten to hurt people with them. But where the former was first and foremost teen romance and luxury porn, the latter is primarily a horror movie stretched over the better part of a decade. Technological literacy separates the Liars from their parents, from law enforcement, and eventually from people their own age — but just the ones who haven’t been grappling with digitally enabled terrorism for their entire adolescences, and therefore don’t need to spend chunks of each day trying to figure out which apps are recording their location, or whether a crucial video file can be corrupted remotely.

The way this shared hell isolates the series’s central group of four smacks of the reality of being harassed and tormented online — to a lot of people, someone complaining about social media bullying might as well be describing a ghost that’s bothering them, or the alien transmissions that won’t leave them alone. It may be a coincidence that this show peaked in popularity in tandem with Gamergate, but it’s a fascinating one. The faux-helpful directive “just log off” still requires lengthy rebuttals from adults who work online and are called upon to explain why harassment is such a toxic problem. Pretty Little Liars is for a younger cohort, and the narrative presupposes the ludicrousness of such a suggestion.

None of the Liars ever prep a plan to go off the grid. It would be stupid, illogical, and bad TV. Instead, the writers dive into the physical and emotional effects of that catch-22, pushing the core friendships to rely on constant communication and self-taught tech savvy, even when the characters would love to get as far away as possible from lock screens studded with notifications.

Pretty Little Liars’ particular brand of screen-mediated horror gradually bled over into film and other television — take the Skype window that frames every gory death in Leo Gabriadze’s Unfriended. Or consider Mike Flanagan’s Hush, a SXSW standout snapped up by Netflix last year. That film gets all its mounting tension and then its denouement, from a FaceTime call. It’s not surprising that art would pick up on new technological fears, as art always does. But it is notable the Pretty Little Liars was first (by miles) to the idea that our gadgets don’t have to literally turn into monsters to be carriers for them.

The sprawling storyline has pushed off gratification for way too long at this point to expect anyone to wait much longer, and I for one am sick of the characters. (Except Hanna!) But I’ll miss this weird, wild show that knew exactly what world it existed in. As always, all you have to do to find the high-minded pop culture that doesn’t feel like a chore: follow the teens.

Pretty Little Liars season 7B premieres tonight on Freeform.