Single-player
According to the game's executive producer Marty Stratton, the key principles of Doom's single-player mode are "badass demons, big effing guns, and moving really fast". The game allows players to perform movements such as double-jumps and ledge-climbs throughout levels of industrial and corporate fields of a Union Aerospace Corporation (UAC) research facility on Mars and then levels of Hell, as the combat system puts emphasis upon momentum and speed. The approach is known as "push-forward combat" which discourages the players from taking cover behind obstacles or resting to regain health while playing from the "Doom Slayer"'s perspective. Players instead collect health and armor pick-ups by killing enemies. "Glory Kills" is a newly introduced melee execution system; when enough damage has been dealt to an enemy, the game will highlight it and allow the player to perform a quick and violent melee takedown as well as reward the player with extra health.
The game features a large arsenal of weapons which can be collected and freely switched by players throughout the game and require no reloading. Recurring weapons of the series also make a return, including the super shotgun and BFG 9000. The BFG has a very small ammunition capacity, but is extremely powerful. Similarly, the chainsaw returns, but has been reintroduced as a special-use weapon that relies upon fuel, but can be used to instantly cut through enemies and provide a greater-than-normal drop of ammunition for the player.
Many enemies also return from the original game, such as the Revenant, Pinky, Mancubus, and Cyberdemon, with many also redesigned. Doom's campaign was made to be over 13 hours long, and the "Ultra-Nightmare" difficulty level features permadeath, which causes the savegame to be lost once the player dies. The campaign also features 13 maps.
Many of the levels have multiple pathways and open areas, which allow players to explore and find collectibles and secrets throughout the levels. Many of these collectibles can be used as part of Doom's progression system, including weapon mods, rune powers, and Praetor Suit upgrades. Weapon points come from field drones and allow the player to unlock alternate modes of fire for many weapons, such as explosive shots and different rate and output of firepower. Each of the weapons' firing modes can be further upgraded using weapon tokens, but they can only be maxed out by completing a challenge related to that particular firing mode. Runes transport the player to a separate arena to perform a combat challenge that grants different abilities when successfully completed, such as better equipment drops from fallen enemies. Players can also upgrade their "Praetor Suit" by retrieving special tokens from dead marines and using them to improve functionality such as equipment, navigation and resistances. Other pickups include small Doomguy figurines and data files that expand on the characters and story.
Additionally, each of the game's levels contains a hidden lever which opens an area extracted from a classic level in the original Doom or Doom II. Finding each of these areas unlocks them, making them accessible from the game's main menu in a section called Classic Maps.
Multiplayer
In Doom's multiplayer mode, several modes, such as team deathmatch and its variation "Soul Harvest", as well as Freeze Tag, Warpath (King of the Hill with a moving 'hill'), Domination, and "Clan Arena" (team last man standing with no pickups), exist within the game. Players can also use power-ups and teleporters in a multiplayer match. They can pick up a Demon Rune, one of the power-ups featured, to transform into and fight as a demon. There are four demons available initially in the game, each of which has different abilities: the Revenant, the Baron of Hell, the Mancubus, and the Prowler. At launch, the game featured nine maps.
Players will be granted experience points upon each match. After they have collected sufficient experience points, players can level up, by which new armor, skins, weapons, and power-ups would be unlocked for players to use. Both the player character and weapon can be customized extensively by applying new skins and colors onto them. In addition, players can receive hack modules while playing the game, which are special abilities that can only be used once after they are collected. There are six types of modules. Scout reveals the locations of all enemies to the player for a limited time after respawning, while Vital Signs shows all enemies' health. Retribution allows players to track their last killer by showing their health and location, while Power Seeker guides players to the power weapon pickup in the game. The Resupply Timer, meanwhile, shows the respawn time of the power-up items. Players can also perform taunts in the game's multiplayer.
On July 19, 2017, Update 6.66 was released for Doom's multiplayer. Update 6.66 features a revised progression system, all three DLC bundled into the core game, a new 'rune' system (replacing the Hack Module system) and enhanced kill notifications. Update 6.66 required everyone to reset their level and gave players the option to retain all unlocked items or reset them. Players who played before Update 6.66 and players who obtained the 'Slayer' level received unique medals to show their status.
