To anyone who can hear this: Proceed to Mercy Hospital for evacuation. I repeat: Proceed to Mercy Hospital for evacuation.

I can’t recall how many times I’ve heard this over the past 10 years. Left 4 Dead first showed up in my life as merely a dream: my PC would barely showcase the main menu without taking me back to the desktop with a crash message. And, perhaps without realizing it, the game became the reason why I upgraded graphics card in order to play it. I’ve never looked back since, clocking over hundreds of hours on it.

We could discuss many of the aspects why it became such a huge game, how it set the foundations of the sequel or perhaps dive into its ridiculously large modding scene, but for its 10th anniversary, I want to talk about how it all began. And, in this case, that means remembering the first campaign of the game: No Mercy.

A chopper flies through a desolated city while a group of survivors prepares for the night of their lives. The biker Francis, the college student Zoey, the Vietnam veteran Bill, and the Junior Systems Analyst named Louis gather together, grabbing their weapon of choice and a medkit. Following the flying message, they start chasing the helicopter in the midst of a zombie outbreak shooting everything in sight, and quickly learning there is friendly fire enabled for default.

You know how the stereotype of a zombie had largely been to portray them as slow-moving beings, often being more on the dumb side than anything? Well, in Left 4 Dead, zombies could run. And folks, let me tell you: they run fast.

We are talking about 28 Days Later level of undead aggressiveness. Hordes await for you in every street, expecting for the slight miscalculation from your part to go forth. Shooting a car and making the alarm go off might attract hundreds of them in a matter of seconds, along with causing your teammates to shout at you over the microphone. And zombies can also climb over fences and pretty much anything that gets on their way. Once they spot you, you better be ready to either confront or run, as they will stop at nothing to get at you. Don’t expect any bites, though. They just hit you furiously until you’re gone for good.

No Mercy isn’t just the beginning of the story for these survivors, but also for the players themselves into this world, and more importantly, its pacing. Left 4 Dead is a quick, often unmerciful game, in which cooperation is key to success and a mandatory element in high difficulties. Learning the best way to quickly get to the checkpoint, marked in the game as safe houses where one can take some rest, resupply, heal their wounds and, well, finally go to the bathroom, appears as a natural instinct after the first few hours. Same goes with weapons, looking for the best “builds” alongside teammates, like carrying two shotguns to open a path ahead while the rest focus on taking down the special infected, such as a Boomer waiting to jump on the group or a Smoker, preparing to capture a wandering survivor.

And everything surrounded it carried a lot of style back then, which has been translated almost perfectly (more on that later) upon the sequel. The premise behind the game makes it look like an ongoing story divided in movies. The film grain might help, too, but it’s the iconic posters that helped to shape that general feeling. Additionally, the AI system behind the game, which takes care of infected or supplies spawns depending on the party status, goes by the name of The Director. This virtual entity is the scenographer who, depending on how things are going in a campaign, will make the team’s lives harder or a bit easier, depending on the difficulty of course.

But the biggest element that didn’t manage to endure is Left 4 Dead: 2 is, plain and simple, fear. The way level design introduced itself in every corner of the campaigns made for claustrophobic escapes. One could be scared to open a door inside a building as much as being alone on an illuminated street with plenty of room to spare. The uncertainty, and how aggressive the game could become in a matter of seconds just when you were enjoying a moment of respite made the game feel unique from similar experiences such as Killing Floor or No More Room In Hell.

There’s one time I would never forget in my passing through No Mercy. During an online match, we reached the hospital with more than a few scratches, but the way out was almost there. We could feel it. Thing is, we had to wait for the elevator to pick us up in order to get to the roof, where the chopper was set to arrive soon. And that meant hordes of undead were just waiting for us to press the button.

To those unfamiliar with No Mercy Hospital, that’s the place where the latter half of the campaign takes place. Just in the end of the second chapter, right after fighting your way through the sewers system, you meet the colossal building. There is a vast number of stairs and floors that you need to cross in order to reach to said elevator, which is your only ticket to get to the roof. It’s an obscure scenario, filled with pitch dark rooms and undead patients still wearing their robes. And waiting for the elevator takes forever, demanding a serious defense plan to hold your ground.

We pressed the button and they started coming. Shotgun shells bouncing on the floor, flashes of light after each shot and blinking lights illuminated the place. There were blood splatters everywhere, and the marching wave of enemies seemed like it would never cease. It proved to be too much for my team, and we were quickly beaten down, one by one. I was the last person standing.

Matchmaking had made Louis my selected character for this run, and I discovered something I hadn’t seen in the years since first playing the game. I took refuge in a room, barely standing anymore due to my low health. Zoey lifted me up when I fell minutes prior, but I could barely see. Pictures of a doctor bed and medical tools in black and white surrounded my sight. And in that moment, Louis started humming a song in a low tone. While I couldn’t see him, I could fear his sweat, his hands shaking. The sound of yet another horde could be heard again, getting closer and closer, until they found him.

As I play through No Mercy once more to remember these moments, I get surprised at how it managed to withstand the passage of time. Zombies still managed to scare me. Hearing the music that indicated a Tank was about to attack us woke up all my senses. And the hospital was still there, just as I remembered it, waiting for me and my group to get to the chopper, with the illusion that it was the one-way ticket out to safety from this nightmare.

Left 4 Dead is now 10 years old, and during that time, thousands of stories were created seamlessly. Anecdotes with friends, late night LAN parties, and hearing Francis’ voice lines complaining about pretty much anything will remain in our minds forever. But it’s valuable to remember how it managed to create a B-movie experience that was not only fun and challenging but also scary, even with company.