At its best, Doom is everything it should be: a single-player campaign that’s just you, your super shotgun, and barely the amount of ammunition required to kill every single demon on Mars. It feels like a Doom game as you desperately try to find health pickups to keep you going, an ever-growing menagerie of demons snapping at your heels. It's exhausting and exciting and a little bit dumb, and when you're into it you're all the way in. At its worst, Doom is a repetitive series of enclosed rooms filled with demons, all of which you must kill to advance, complemented by a derivative and poorly thought-out multiplayer mode.
First impressions wise, Doom strikes all the right notes. The Union Aerospace Corporation's research facility on Mars runs red with the blood of employees who’ve learned a new meaning for the phrase 'wrongful termination,' but that barely matters to the inexplicably mute Doomguy, who shoots anything and everything which moves. Starting with only the pistol encourages you to focus on the diabolically delightful Glory Kill system — shoot your nearest Demon enough that they become staggered and highlighted in blue or orange, and if you press F (or R3 on a PS4 controller) while standing next to them you will rend them asunder. That is to say, you'll tear off their limbs and, in more than a few cases, joyfully beat them with their own appendages.
Lifted wholesale from the still-popular Brutal Doom mod for the original Doom, developer id Software smartly uses these executions to maintain momentum as you play. An executed enemy will drop health packs — critical pickups in a game where you don't regenerate your health out of combat. As you make your way through the UAC facility, the purpose of those health packs becomes clear: They allow you to sprint headfirst into combat (Doomguy's default movement speed is a steady run) and kill as many enemies as you can. If you take too much damage, or if you're running low on ammunition, it’s easy to recover by staggering demons and performing an execution, which gets some health back and removes a threat without using as much ammo. Executions teleport Doomguy a short distance to his target and render him temporarily invincible while they’re carried out, which makes them great for two slightly left-of-centre things — getting a moment's ironic peace in the middle of a firefight, and teleporting yourself loose when you clip through the floor (which happened to me more than a few times).

The demon outbreak on the facility is a result of worst business plan of all time  to rob Hell of its energy resources — and security precautions see to it that you cannot open most doors if any demons are still alive. These are kill chambers, a relic of an era of shooter design all but gone, designed to contain you and force you into a particular playstyle. Where games with regenerating health reward players who hide and pick off enemies one at a time, Doom instead forces you to map out a path through the chamber trying to find health without ever stopping long enough to become overwhelmed.
It's a design philosophy which runs counter to the nature of the execution system. Glory Kills promote a forward momentum, encouraging you to move towards enemies to close the distance and earn your health pickups, but the kill chamber map style does the opposite. Your best strategy is to move backwards through the chamber, away from the enemies, and to do damage as you go. The AI in Doom is not particularly smart, and you can rely on it to roughly converge on your location (even when it can't see you and shouldn’t know where you are). So if you run in circles around the kill chamber, shooting behind you and dodging projectiles, you can kill the majority of the enemies within — only after you've thinned the herd of Demons can you then start running forward and killing them by circle-strafing (running around them in circles).
It might seem like an odd complaint, because I've praised Doom for how old-school it feels, and circle-strafing in kill chambers is an old-school staple. But in the old days rooms like these were products of an era where enemy AI wasn't capable of the surprisingly scary tactics we see in shooters these days. In Doom it seems more like a crutch — if the enemies were more capable of advanced tactics and teamwork the shooting would be more interesting, and I wouldn't need to be locked in a room to want to kill everything in sight. That doesn't mean it's bad, but it's just about the only trick up Doom’s sleeve, and it doesn't take too long before it wears thin.

The quality of the shooting itself varies depending on which of the eight weapons you use. The Super Shotgun is brilliant — good enough that by the end of the campaign I was only using other weapons long enough to get shotgun ammo back. The beautiful finish on the double-barrel gun captures the nostalgic vibe of the older games while delivering a hefty wallop across a wide spread, which makes it great against the bigger enemies you end up fighting dozens of. On the other end of the spectrum is the Rocket Launcher, which feels underpowered and redundant. Especially after you’ve upgraded the Heavy Assault Rifle and the Combat Shotgun to posses explosive alternate fire modes, the Rocket Launcher barely seems worth the effort required to draw it. Weapons sharing ammunition between archetypes – like the Plasma Cannon and Gauss Rifle both using plasmoids – is an odd concession to nostalgia, because you get all the weapons quite early (especially if you're hunting for secret areas). This meant my use of weapons like the Combat Shotgun were relegated to accidental weapon switches, because I was leary of using up my Super Shotgun ammunition on the weaker of the two guns.
Of course, The BFG 9000 makes an appearance and occupies an interesting place in the weapon lineup. Moved away from the weapons wheel, the BFG has its own dedicated button (T or Triangle) which emphasises its importance in your arsenal. When you fire it, it vapourises everything in a very large radius: green ionic charges arc from the first enemy you hit and into every other demon nearby, and the gibs soon fill the air like confetti at an environmentally irresponsible parade. It's a quick-charging Win Button, but that's what the BFG is supposed to be. The only drawback is that it's so powerful, especially if you train your enemies behind you into an easily obliterated mob, that I often found myself holding off on using it, waiting for bigger waves to arrive... until suddenly everything was dead and I didn't get to use it at all.
Those hordes of demons come in all shapes and sizes. The enemies start out quite tame, a wide array of lumbering zombie types for you to gib and execute at your leisure. As the campaign progresses the demons start to grow, trading warped humans for bigger, meaner monsters direct from Hell, including the iconic lineup of classics The Pinky demon returns to provide a fantastic fight: your first encounter with this squat, blister-red charging demon is tough, because he closes the distance so quickly and shrugs off most shots to the face. Eventually Pinkys will be the cannon fodder you fight as you concentrate on more pressing threats like the cycloptic Mancubus, which has guns for arms and does long-range, mid-range, and short-range damage. The Barons of Hell were my favourite to fight, despite their relative simplicity. Towering demons with horned heads and chitinous armour plating beneath their skin, they rely on close-range attacks and are capable of getting into range very quickly. My one complaint about the monsters is that the possessed grunts which make up the bulk of the cannon fodder sound amateurish. Part gargle, part screaming, their repetitive ambient cries for attention grate on the nerves well before halfway through the campaign.
The only enemies more imposing than the Barons of Hell were boss fights, where Doom takes on a very different feel. The bosses possess a wide array of attacks which turn them into dexterity-based puzzles. Shooting them in the face while running backwards won't work against these enemies, so you need to work out their attacks, figure out how to dodge them, and shoot whatever their weak spot is. I don't want to spoil them so I'll avoid specific details, but one boss fight will test the limits of your ability to dodge in 3D space as it hammers you with long-distance attacks. Shooter bosses are so often massive bullet sponges and little else these days, which makes Doom's big fights feel that much more satisfying to win. In each boss fight I died at least twice just trying to memorise the way the attacks were telegraphed as well as the best way to avoid them.
Doom's biggest concession to the new school of shooter design — progression by way of a weapon and armour upgrade system — is definitely for the best. It encourages you to seek out the levels’ many secrets, confident your diligent scrounging will be rewarded with an expansion for your health pool, the opportunity to improve your rocket launcher, or an upgrade for your body armour which allows you to switch weapons faster.
In that specific way, the level design — when it isn't locking you into a room filled with demons — is brilliant. The approach creates an organic flow to accommodating you depending on how you want to play. If you just want to skip from kill chamber to kill chamber you can, but you'll inevitably notice out-of-place elements to investigate, and you'll begin to understand the breadth of the level itself as you go. A casual secret-hunter will come across upgrades just by taking the path less travelled, but there are tiers above that. A committed hunter will always be on the lookout for oddities in the otherwise perfect placement of the levels, and they'll need to do some solid first-person platforming to reach their objective. The really keen secret-finders will wind up making some spectacular leaps of faith in their quest to reach runes, collectable Doomguy dolls, and upgrades. The layers of secret building, along with the platforming, lead to an opportunity for you to dictate how much downtime you have in between high-octane killathons, and it's a great way to grab a breather.

Performance-wise, Doom is id Software's best game in recent memory. Rage had oodles of problems even for those lucky few with the right combination of PC parts, but Doom's biggest flaws thus far have been a few error-less crashes to desktop and some extremely odd clipping issues. Outside of a handful of errors it ran at a solid 60 frames per second on my GTX 780, and it looks great while doing so. The way it handles lighting is sometimes reminiscent of Doom 3's too-dark world, but here no time is wasted in illuminating things. The same attention to detail paid to the level design has been given to the world art, which means there are always interesting elements of the world to infer from the environments, like vehicle repair bays filled with the equipment necessary to fix the Mars-roving trucks on the base, including stacks of spare tyres. The only trick here is that you need to slow down enough to actually look.
In the multiplayer portion of Doom the tone is dramatically different. Where the single-player portion of Doom is primarily old school with a few new tricks, multiplayer borrows heavily from modern shooters, forgetting its roots and in turn becoming unmemorable.
Like Halo, Call of Duty, and most other modern shooters, Doom restricts you to just two weapons, but it gives you both weapons when you spawn. This means you get to start with the Super Shotgun and the Plasma Cannon if you wish (although here, unlike in the campaign, the Combat Shotgun is actually superior to the Super Shotgun). This isn't inherently bad — after all, it works in dozens of other games.

The problem arises when the old-school elements rear their head and collide with the new. Without regenerating health or armour, you're forced to rely on the health and armour collectibles scattered around the map. Again, this isn't a bad thing in and of itself, but the influence this has on the level design is significant. With the need to create logical spawn areas for these very necessary survivability tools, levels are created with a flow in mind, giving them a very old school feel as you dash through from item to item. Staggered sight lines allow you to spot a pickup from afar and then make your way to it, collecting smaller items along the way. With luck you'll return to full health before you encounter another competitor. In older arena shooters, this architecture created areas of conflict — while you might be constantly moving to get your health back to full, your objective on the map was the weapon. If you really wanted the Rocket Launcher, you'd bounce from health pickup to armour pickup until you reached it, and because it was a popular weapon you'd no doubt run into some resistance when you arrived. Before Capture the Flag or Domination created obvious conflict zones on maps, pickups dictated conflict — which is why Team Deathmatch wasn't as big a bore as it is these days.
Thanks to Loadouts, pickups on the map are either relegated to health, armour, and ammunition, or they're elevated to powerful instant-win items. Quad Damage, Haste, and Regeneration all spawn in fixed places on Doom’s maps, as do power weapons like the one-shot kill BFG and Gauss Rifle or the chainsaw. With weapons assigned on spawn via loadouts, the number of potential conflict zones is reduced — on most maps to just two — and because power items are typically hidden (to a degree) areas of conflict are basically random.
The exception is the Demon Rune, which spawns at random around the map and allows you to transform into one of four demons. Each demon has its own advantages and disadvantages, but all four have significant, devastating advantages over regular players. Take the Baron of Hell for example. Taken straight from the single-player campaign, the Baron moves faster than normal (probably because his stride is three times longer) and can instagib any enemy close enough to him with a devastating melee. On top of that, he can smash the floor before him, creating a channel of spikes in front of him which, again, instagib any enemy close enough to him. He has 750 health, more than three times the maximum potential of any regular Doomguy, and he represents virtually guaranteed kills for anyone who gets the Demon Rune. In every mode except for Soul Harvest the demon lives on a timer, and when the timer runs out you return to your original form. This is a problem, because it creates a significant balancing problem in team modes. Whichever team gets the demon will have an advantage. Because the demon is on an expiring timer and not a permanent fixture, when it randomly respawns later in the match it might give the advantage to the same team which got it the first time, and there’s nothing the other team can do about it. Two evenly matched teams' chances of victory are reduced to a flip of a coin.

In Soul Harvest killing your opponents isn't enough; you must collect the souls of those you kill. Demons are worth four souls each, which means a demon needs to kill at least three enemies to make up the potential deficit. There's more to the equation, which evens things out for Soul Harvest — first blood spawns the Demon Rune itself on the dead body of the match's first victim, and after this the Rune will remain in play for the rest of the round. Usually it trades from team to team throughout the match, although you're more than capable of retaking the Demon Rune once it unlocks for your team. Because both teams get a theoretically even amount of access to the Demon Rune, the demon itself becomes a conflict area on the map as players from both sides try to use it to their advantage. This means the demon is hunted, not avoided, turning the Demon Rune into a risk vs reward scenario, which is what it should be.
Doom also includes an easy-to-use level editor, called SnapMap, and the community creations that’ve sprung up from it are already the highlight of the multiplayer experience. In SnapMap you can create your own levels for competitive or cooperative multiplayer, and it's as easy as snapping together pre-built level tiles. The tutorial is fantastic, helped along by the simplicity of the tools themselves, which means you can get started making your own dream map in no time. The simplicity has its drawbacks, chief amongst them being that SnapMap is not a replacement for a full modding SDK, so while you can create some amazing things with it you won't be able fundamentally change the nature of Doom itself. While making shooter levels is possible, you can't really transform Doom into an RTS the way you can turn StarCraft 2 into a shooter.
Nevertheless, limitations lead to creativity, and nowhere is this better evidenced than in the Community map area. You can publish your created maps for the world to inspect and enjoy, and through the same system you can see what others have put together. A community map I played was a cross between an incremental clicker and a dungeon crawler — something like the browser-based do-nothing hit A Dark Room. You click on farm areas to water plants which turnover seeds, which you spend on creating more plants. Once you have enough plants creating seeds, you can spend those seeds on accessing some mines, and only upon reaching the end of the mines do you complete the level. It was such an oddity at every level that I couldn’t help but find it endearing.