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Level 4 — Computerkrimis (computer mysteries) is a series of German middle grade novels by Andreas Schlüter, originally released between 1994 and 2007. The protagonists are a group of thirteen-year olds — the main four are tech wiz Ben, his athletic best friend Frank, the smart and skeptical Jennifer, and Fiery Redhead Miriam, often accompanied by friends such as the somewhat spacey collector Thomas and Bully Turned Buddy Kolja — who keep getting sucked into Science Fantasy adventures involving computer games, hi-tech inventions, robots, time travel, and virtual reality.
The books in the series are:
- Level 4 — Die Stadt der Kinder (1994): When Ben plays his new computer game called The City of Children, he finds that it has suddenly become reality — everyone older than fifteen has disappeared. The kids must learn to deal with the situation, fight schoolyard bully Kolja who attempts to seize control of the city, and figure out how to get to the elusive fourth level and beat the game. This book was also released in an English translation (named Level 4 — Kid City) for German students with vocabulary annotations.
- Der Ring der Gedanken (The Ring of Thoughts, 1995) — Ben finds a ring with a computer chip in it that gives its owner the power to read other people's thoughts. Trouble ensues when the kids find out their math teacher programmed the chip and Kolja gets his hands on the ring.
- Achtung, Zeitfalle! (Caution, Time Trap, 1996) — On a class trip to Florence, Italy, the quartet and the newly reformed Kolja find themselves seemingly having travelled back in time to the sixteenth century. They figure out that they are in a computer simulation, but there is no obvious way back to reality.
- Jagd im Internet (The Internet Chase, 1997) — Ben and Frank spend their summer vacation on a small German island while Miriam and Jennifer are on Mallorca. Thanks to that newfangled Internet invention with its emails and chatrooms, the kids can still communicate. When they stumble upon an online contest that promises the winner twenty million German marks, they uncover a criminal plot behind it.
- UFO der geheimen Welt (UFO from a Secret World, 1998) — Frank disappears after seeing a flying saucer. While searching for him, Ben, Jennifer, Miriam, and Thomas discover a secret world beneath the ocean populated by robots in the midst of a conflict.
- Flucht vom Mond (Escape From The Moon, 1999) — While visiting a space station, the kids accidentally take off in one of the rockets, having gotten mixed up with some youth delinquents who were to carry out their sentences in a secret correctional center on the moon.
- 2049 (1999) — The quartet and Thomas take part in a brain scan experiment and awaken fifty years in the future. While dealing with the dystopian world of 2049, they find out that they are not themselves, but rather the results of the brain scan, the memories of their 1999 selves having been placed in artificial bodies.
- Chaos im Netzwerk-Clan (Trouble in the Network Clan, 2001) — What was supposed to be a regular LAN party night takes a strange turn when the group encounter aliens — small, wormlike creatures who need their help to get back home.
- Die Spur des Hackers (Trace of the Hacker, 2002) — Ben's connections to the hacking scene get him into hot water when a friend of his whom he shared files with gets arrested for targeting a major software company.
- Reality Game (2003) — Frank is a contestant in a reality show where teenagers solve tasks all over various towns while trying to avoid being recognized and captured. But secretly, the show is an experiment, the contestants having been implanted a sense-enhancing computer chip.
- Level 4.2 — Zurück in der Stadt der Kinder (Back in the City of Children, 2004) — The group find themselves back in a world with no adults, but this time, authority figures exist — kids whose brains have apparently been reprogrammed.
- Der Sunshine-Chip (The Sunshine Chip, 2005) — The group takes a vacation in a dome with artificial tropical weather. The technology goes out of control, causing tornadoes and avalanches.
- Level 4.3 — Der Staat der Kinder (The Children's State, 2006/2007, originally published in two volumes) — In the series' Grand Finale, adults have vanished once again, and the town initially appears completely empty. While building up a society, the group finally meets the the brain behind The City of Children.
The book series provides examples of:
- Adults Are Useless: In the first book, the kids realize that adults are decidedly not useless, as they take care of all the stuff the kids take for granted. Despite this, all subsequent books play the trope straight; with a couple of exceptions, adults are either villains, obstructive authority figures, well-meaning but clueless, or just absent, with the kids solving pretty much all of their problems themselves.
- And Then What?: When Kolja attempts to take over the adultless town, the heroes ask him what he actually wants to do with his powers. This flusters him as he didn't think any further than wanting to be the boss.
- Arbitrary Skepticism: The characters, particularly Ben and Jennifer, tend to react to every new weird adventure with disbelief at first despite everything they've gone through before. When Frank claims to have seen a UFO, his friends just laugh at him, although it's hardly much crazier than, say, getting sucked into a video game.
- Cassandra Truth: When the quartet disappear thanks to the aliens, the others for once decide to involve their parents, but they just believe the kids are imagining things.
- Collector of the Strange: Thomas collects everything he finds, as long as it's free. His parents' garage is filled to to the brim with stuff, from broken pens to old paintings. He prides himself on being a treasure hunter and having a sixth sense to find things. His ability indeed often turns out to be very useful, but as he is always on the lookout for something, Thomas is also incredibly (physically) slow.
- Comic-Book Time: The kids remain thirteen to fourteen throughout the series, but as far as the reader can tell every book takes place in the year of its publication. There are contemporary references throughout — for example, the currency changes from D-Mark to Euro; Miriam mentions Big Brother being the only good thing on TV in 2001's Chaos im Netzwerk-Clan; 2005's Der Sunshine-Chip makes references to the then-recent election of a German pope and the upcoming World Cup in Germany. In 2049, which came out in 1999, Ben explicitly says he was born in 1986.
- Conveniently Coherent Thoughts: The mind-reading ring only reads thoughts that are in fully coherent sentences.
- Clone Degeneration: In 2049, the program that copies peoples' old selves into new bodies begins to malfunction, resulting in personality switches and mind melding.
- Dirty Mind-Reading: A kid-friendly version in Der Ring der Gedanken, where Ben reads Jennifer's mind just when she thinks about him being very cute, much to his embarrassment (and hers, as she immediately figures out what happened).
- Elaborate Underground Base: In UFO der geheimen Welt, the kids discover a secret world beneath the ocean, meant to be a living space for a global elite to inhabit once the earth's surface becomes uninhabitable.
- Enemy Mine: Kolja and the others decide to work together to stop their teacher at the end of Der Ring der Gedanken. Afterwards, he's never an antagonist again.
- Fiery Redhead: Red-headed Miriam is the brashest and most outgoing member of the group.
- Free-Range Children: The kids are usually free to go wherever they want, even taking vacations on their own. Gets Hand Waved by the narration stating they always have to beg for a long time, but once one set of parents gives in, the others always fall in line.
- Future Spandex: In 2049, people wear garishly-colored, transparent full body suits (with only the most private area being covered) so they cannot hide weapons under their clothing.
- Global Currency: "Weltdollar" in 2049.
- Government Conspiracy: In UFO der geheimen Welt, it's revealed that the governments of some of the world's most developed countries have already conceived and built an underground world to live in when the earth's natural resources dry up; in Flucht vom Mond, it turns out humans have already built permanent bases on the moon and space tourism is already a thing.
- Hide Your Children: In Die Stadt der Kinder, not only are the adults gone, babies and toddlers also have disappeared. Ben points out that in the game, the adults' disappearance is explicitly the premise, but children below a certain age just don't exist in first place, and since everything functions by the rules of the game, they have vanished as well.
- How Unscientific!: The majority of the books involve man-made wonders, no matter how farfetched. UFO der geheimen Welt stresses the nigh-impossibility of aliens both co-existing at the same time as us and being able to travel to our world. But then in Chaos im Netzwerk-Clan, aliens just appear.
- Humans Are the Real Monsters: One of the robots shows the kids footage of various human atrocities to argue the point they would be better off ruling the earth.
- I Just Want to Have Friends: Thomas sometimes worries that he isn't taken seriously by the others. The truth is that they all do like him, but his occasionally weird behavior also sometimes exasperates them.
- Immoral Reality Show: The titular Reality Game uses teenagers to as unknowing test subjects for new technology.
- Long-Runner Tech Marches On: Aside from the science fiction elements, the books reflect the technology of their times. Cell phones don't exist in the first few books, but are ubiquitous later, even if Jennifer still doesn't find them necessary. Jagd im Internet is filled with exposition about how the early internet worked (Miriam asks what an email is at one point); Chaos im Netzwerk-Clan features a LAN party, which were at the height of their popularity around the turn of the millennium; in Die Spur des Hackers from 2003, the recently invented USB flash drives are a plot element, and so on. Also, the titular game of the first book appears to be a very generic mix of platformer and adventure game; even in 1994 it seemed a little strange that Ben would be that obsessed with it, but the 21st century version of him definitely wouldn't care (the sequels avoid bringing up the game directly).
- Mechanical Evolution: The non-Three Laws-Compliant robots in UFO der geheimen Welt eventually started building more of their own.
- Missing the Good Stuff: Thomas is always worried about missing out on an adventure, and complains loudly when he does so at the end of Achtung, Zeitfalle. By the time of Der Sunshine-Chip, he takes active steps to defy it by signing up the others up for a vacation without asking them first, arguing that something always happens when they are involved. Sure enough, he's right.
- My Future Self and Me: In 2049, while stranded in the future, the group makes a friend who brings them to his uncle. It's made clear to the reader that said uncle is an elderly Ben. There is no Future Self Reveal, however; Ben at one point gets suspicious about the uncle seemingly knowing stuff about the group he shouldn't, but due to various events happening, he never gets to question it further.
- New Technology Is Evil: Jennifer often espouses this view, being extremely skeptical of the excesses of modern technology.
- No Full Name Given: Except for Frank (Zöllner, and later Zeuner) and Jennifer (Barlow), none of the protagonists' surnames are ever revealed.
- Oddball in the Series: Two of the thirteen books (Jagd im Internet and Die Spur des Hackers) have no science-fiction elements, being crime thrillers instead.
- Pair the Smart Ones: Ben and Jennifer, the two smartest characters in the group, end up together.
- Ridiculous Future Sequelization: In 2049, the characters see an advertisement for Star Wars — the fourth trilogy. The book came out in 1999, when the prequel trilogy had just started. Nowadays, of course, it seems like a conservative guesstimate.
- Science Fantasy: The first book is the most straightforward example, with Ben taking over the role of the wizard in the computer game and gaining magic powers.
- Sensitive Guy and Manly Man: There's brainy, sensitive Ben and the docile and slightly awkward Thomas on the one hand and sports-obsessed Frank and loud-mouthed, brutish Kolja on the other.
- Space Base: A youth correctional center exists on the moon.
- Status Quo Is God: While there are a few Continuity Nods and permanent changes (most notably Kolja's Heel–Face Turn), previous adventures never have any serious repercussions. In particular, the events of Flucht vom Mond should have resulted in a huge fallout and made the kids celebrities, but they're never addressed again. Time travel also gets called explicitly impossible in 2049 despite the kids having done just that two books before.
- The Story That Never Was: The kids go through a wormhole at the end of UFO der geheimen Welt and travel to a point in time before Frank's disappearance, thereby erasing their adventure.
- Switching P.O.V.: The books are told in third-person narration with constantly changing points of view, so the reader gets to hear everyone's thoughts throughout every story.
- Take That!: A none-too-subtle one in Die Spur des Hackers, where the evil software company is called Protzosoft, protzen being the German word for "to show off" or "to flaunt".
- Teenage Wasteland: After the adults disappear, the city threatens to become this, as kids wreck havoc in the mall and Kolja and his gang attempt to take over the town.
- There Are No Adults: The premise of The City of Children, both the game within the book and the book itself.
- Three Laws-Compliant: The robots in UFO der geheimen Welt were built to adhere to the principles, with the exception of some military units.
- Trapped in TV Land: The characters get trapped in a computer game in the Level 4 trilogy (or, to be more precise, reality changes to function by the rules of the game) and in cyberspace in Achtung, Zeitfalle.
- True Companions: The main quartet. After the first book it's repeatedly stated that Frank is always with Ben who goes nowhere without Jennifer who always hangs out with Miriam.
- Turned Against Their Masters: In UFO der geheimen Welt, the advanced military robots have decided that they are the natural successors to humans and will take over the earth. However, they decide to wait out the time until humanity does itself in, having made the underground base conceived by a global elite for that situation uninhabitable for humans.
- Verbal Tic: Token Minority Achmed adds "ey" to nearly all of his sentences.
- Weather-Control Machine: In Der Sunshine-Chip, the kids find out a program exists that sells any kind of weather to companies and governments all over the world.
- Weirdness Magnet: Occasionally lampshaded when the kids wonder why they keep stumbling into crazy adventures, but as there's no overarching plot, there's no explanation either.
- Welcome to Corneria: In Achtung, Zeitfalle, the kids realize they haven't time travelled and are instead in a simulation when the other people begin to repeat their dialogue and actions.
- What Happened to the Mouse?: In 2049, the kids' new friend's uncle tells them he stole a box of whiskey when he was Ben's age. Unbeknownst to the kids, the uncle is an elderly Ben, and for the reader, it appears to be setting up an event in a later book, but Ben never steals a box of whiskey at any point in the series. Furthermore, he doesn't even have a sibling in the present, which is another potential plot point for a later book that was never followed up upon (at one point it is mentioned that Ben's mom has a new boyfriend, but that's as far as it goes).
