The latest Call of Duty: World War II.

Thankfully, the game is a lovingly crafted and deep experience, one which mines the horrors and glory of the biggest war ever waged for pathos, thrills, and unrelenting tension. The experience is so intense that there are still likely secrets to be discovered: new characters, new achievements, new playing mechanics, even new multiplayer maps.

A little over a week in, players have already unearthed a treasure trove of hidden features involving the campaign, the massive new social space known as Headquarters, and the star-studded and horror-themed Zombies mode.

Whether you're a hardcore gamer or just a casual dabbler in Nazi-hunting, there's plenty to discover in the first Call of Duty title from Sledgehammer Games.

To get you started, here are the 15 Things You Never Knew You Could Do In Call of Duty: World War II.

 Unlock a secret plot and final boss battle in The Final Reich Zombie mode map

“The Final Reich” appears several times on this list, because it’s basically a secondary campaign in the game, only one you can share with friends or random strangers you find on the internet. In the Zombie mode map, you spawn in an alley, fighting your way through horrifying half-dead Germans until you reach a bunker containing yet more Nazi horrors.

Like in Zombie modes of previous games, you can restart the power, unblock doorways, and find Mystery Boxes, but in The Final Reich, these things advance the plot and the map rewards you by unveiling a story told through secret cutscenes and audio recordings.

Finally, if you make it through, you face the Panzermorder, the final boss of The Final Reich, annoyingly missing an umlaut from his name, which means Tank Murderer in German.

Unlock a secret Mystery Box room in the Groesten Haus survival map

The key to surviving the unlockable Groesten Haus is unlocking a Mystery Box to provide the player with more weapons and ammo. Players can earn money through killing zombies and spend it at the Box, which will spit out a random weapon for the player. Unlocking the Mystery Box in the Groesten Haus, though, requires an esoteric solution.

Players will have to find 10 different gas lanterns scattered throughout the Groesten Haus and shoot them all in order to unlock the Mystery Box. Considering that the lanterns don’t really stand out from the rest of the Haus’ décor, it’s a detail casual or first-time player can easily miss amidst the terror of actually trying to survive the waves of fascist undead.

Unlock secret player characters in Zombies mode

In addition to bringing the single-player campaign back to the heady, brutal World War II drama that used to be the series' bread and butter, the Zombies mode has gone back to its horror roots while keeping the triple-A celebrity guests.

Unlike other COD games, here you can actually choose which celebrity character you play as: David Tennant (Blade, Iron Sky).

COD: WW2 Zombie mode even lets the players unlock secret characters by completing five hidden objectives. The objectives vary by the character players are trying to unlock.

For example, players wanting to unlock the Survivalist will need to get to Round 30 without purchasing perks, only using the starting weapon, only purchasing two or less Mystery Box weapons, without turning on the power, and without going down once. That’s right, even if another player revives you, you’ve got to start all over again. That’s the level of difficulty inherent in COD: WW2’s secret characters.

Use a top-secret version of Modern Warfare 2’s Nuke killstreak bonus: the Tactical V2 Rocket

In Call of Duty: Modern Warfare 2 multiplayer introduced a game-changing killstreak bonus known as the Tactical Nuke. If a player managed to get 25 kills without ever dying themselves, they earned the Nuke.

When deployed, it killed all other players on the map and ended the game with a win for whatever side the player who deployed it was on, regardless of which team was actually winning at the time. It was like a more lethal Golden Snitch.

In Call of Duty: WW2, this bonus comes back, though obviously without the nuclear component. Instead, it’s named after the V2 rocket, the German mad science invention that in real life helped lead to space programs worldwide. Only now, the player has to achieve Prestige ranking in all five multiplayer Divisions (COD: WW2’s version of player classes) in addition to getting 25 kills in a single life.

Play classic Atari games for Rest and Relaxation in Headquarters

Activision has been around since the beginning of console gameplay, having designed and programmed games for the Atari 2600. It was responsible for classics like Pitfall (and commercials featuring a young Jack Black) before moving on to other classics like Mechwarrior 2, Spider-Man, and Tony Hawk’s Pro Skater.

They publish the Call of Duty series now, and in the new Headquarters social space in Call of Duty: World War 2, the player can actually play vintage Activision Atari games using armoury credits in place of quarters in the R&R section of Headquarters.

Weirdly, Pitfall isn’t available, but its sequel is, along with classics like Barnstorming, Chopper Command, and River Raid (here inexplicably called River Band). This isn’t the first time Activision has inserted retro games into the Call of Duty series, but definitely the most fun.

Play as women in multiplayer

Let’s all be honest: Call of Duty has pretty much always catered to male fantasies. There’s plenty of things to enjoy if you aren’t a male American, but the plots, characters, tone, and design sensibilities have always catered to macho male military jingoism.

However, in COD: WW2, you can now actually play as a woman in multiplayer. Women like shooters and action too, and any gamer knows that one’s avatar online is like a business card, a statement not only of your tactical prowess, but your personality, your style, your skills.

Personalizing the physical form of your avatar and its equipment is almost as much fun as playing it, and if you’re good enough, players around the world will always your character as the last thing they saw before they caught a bullet that ended the match.

Sledgehammer deserves credit for opening up the spectrum of what gamers can present themselves as online in one of the most popular gaming franchises ever created.

Unlock a secret fireworks achievement in the final boss battle of The Final Reich

Assuming you reach the final boss battle of “The Final Reich” in Zombies mode, you’re most likely just trying to survive. You’re probably not paying attention to every detail, and just trying to repel the horrible undead black-magic Nazi monstrosities that the Final Reich is pumping out with astonishing volume.

However, the best way to defeat the Panzermorder is through an incredibly obtuse process of shooting the circling airship in the boss battle, charging up the batteries it drops by killing zombies near them, then shooting the Panzermorder to stun it and placing the batteries on it.

Do this enough times and when the Panzermorder is dead and you’ve beaten Call of Duty: World War 2, fireworks will appear in the sky along with a corresponding achievement as the credits are rolling.

Unlock an extra Zombies Survival Map, Groesten Haus

Fun fact: Groesten Haus means Biggest House in German. Groesten Haus is basically the tutorial for the Zombie mode, where players can learn the ropes of what the Zombie mode is all about. However, Groesten Haus can become as much of a survival test as The Final Reich, a feature that casual players might not take the time to find out.

Usually, the tutorial ends when the player dies or quits, but the Groesten Haus allows you to survive. The average player who manages to kill every zombie will find that they will have to locate the Mystery Box hidden on the map.

If they do, they can continue playing the tutorial as a full-featured Zombies map, which helps considering the game only ships with one true Zombies map at launch.

Interrupt using a first aid kit by switching weapons

This seems like a no-brainer, but it can make the difference in Call of Duty: WWII. See, unlike Modern Warfare, COD Blops, Ghosts, or Advance Warfighter, you do not regenerate health. Let's repeat that, for every reader who was weaned on modern shooters: you do not regenerate health.

This is to the game’s advantage, in that you are forced to do the math before every firefight, deciding tactics and weapons based on how much health you have to spare and how many health packs can patch you up all is said and done.

Thus, a minor saving grace comes in the form of first aid kits taking time to use. If you decide you used one impulsively, accidentally, or unnecessarily, you can cancel it after you press the “use first aid kit” button by switching weapons.

Shoot through most wooden cover, but not all

Fun fact: wood is not bulletproof. Older action movies tend to ignore this steadfast fact of physics, allowing heroes to crouch behind overturned tables, drywall, and saloon bars to avoid a hail of dastardly bullets.

In a lot of games, this is true as well, if only because it would be exhausting to develop a game engine to differentiate between the materials cover was made out of, so any walls or furniture that players can hide behind shield them from enemy fire.

Refreshingly, in Call of Duty: WW2, most wooden things that enemies hide behind offer no cover at all, as your weapons can shoot right through them, allowing you to take out enemies dumb or panicky enough to hide behind hay wagons or wooden crates.

Realistically, it depends on the caliber of weapon, the type of wood, and what object it’s making up whether your bullets hit home.