You need a NinjaKiwi account to play, and you do not need to go and create one. The Steam purchase block for app 2747660 lists two lines the store page text never mentions: "Requires 3rd-Party Account: NinjaKiwi Login (Supports Linking to Steam Account)" and "Requires agreement to a 3rd-party EULA". NinjaKiwi games create that account for you at first launch, and linking it to Steam happens inside the game when you try to join a multiplayer game.

The player count in Zombie Assault: Resurgence goes up to four, and the game is built to be equally playable in single player as it is in multiplayer. A solo run is a first-class way to play rather than a reduced one, and because drops are based on your individual level, a solo player gets the same rarity of loot as a four-player squad. There is no PvP and no friendly fire, so the only thing a squad can lose to is the horde.

The NinjaKiwi account and linking it to Steam

So on top of Steam's own terms you agree a third-party EULA, and the login you actually play under is a NinjaKiwi one rather than your Steam account.

There is no sign-up to hunt for. NinjaKiwi games create the account automatically at first launch, so you do not go looking for a registration page.

Linking happens inside the game. The prompt appears when you try to join a multiplayer game, and the confirmation is a message in the top-right of the lobby. That is the thing to look for before you queue with friends.

If the link fails, these are the channels that work:

  • The support portal: support.ninjakiwi.com
  • The email address: support@ninjakiwi.com
  • The official Discord: discord.gg/ninjakiwi
  • r/ZombieAssaultOfficial, which carries status posts

Players who bought the game and hit the prompt have fixed it by linking the NinjaKiwi account, and the same route is the accepted answer in the early-access reward threads. The same escalation list is on the troubleshooting page. The same account is also how the Morlok Frostbite Pistol reward is delivered — the weapons page has the claim steps.

Player count: how many players can play

  • Up to four players per squad. The store page lists 4 player co-op or going solo in single player.
  • Solo is fully supported, and several systems are built around a single merc rather than a team.
  • The Steam categories include Single-player, Multi-player, Co-op, Online Co-op and Cross-Platform Multiplayer.
  • The four-player format is what the achievements are built around, including full team extraction in a 4 player squad operation, and finishing one as the top operative. Team Up tracks the first 25 missions or operations completed with two or more players.

Matchmaking takes player rank into account, so squads are matched with players of comparable standing, and team objectives are a major factor in the XP you earn. That last point matters most if you are new: playing for the objective beats playing for the kill count, and support abilities that help the team award XP for healing teammates.

Starting a first run is covered in the getting started page.

Playing with friends

Friends are invited through the game's own social layer:

  • Discord and Steam friends lists are visible inside the game, and Discord and Steam presence is supported.
  • You can invite Discord or Steam friends to your party from inside the game UI, and from the Discord or Steam UI itself.
  • Pending party invitations from Discord friends surface in the game UI.
  • Private parties are supported — you can join or host one.
  • Communication runs on canned chat, plus a ping system for pointing things out, tracked by the achievement Order 99 for pinging squad mates 99 times.

The practical flow is short: pick your merc and loadout in Merc HQ, the hub that also handles matchmaking, queue for an Operation or a Story Mission, vote on the mission and the difficulty, and run it with your squad.

Two things to know before you queue. The game expects a persistent internet connection, so there is no offline fallback to plan around. And if a session drops mid-run, it cannot be resumed — the troubleshooting page has the checklist for that.

Crossplay across PC and mobile

The game is built to run across PC and mobile with the same content on both. Ninja Kiwi has stated that Zombie Assault: Resurgence is the same game across all platforms — no scaled-down versions, no cut features and no compromises depending on where you play, with the full story missions, multiplayer and progression on every platform. The launch was simultaneous on Steam, iOS and Android.

Your progress crosses over. If you buy the game on both PC and mobile, log into the same account on both devices and your data syncs. Steam Cloud is also enabled on the Steam build, so a Steam account carries its own save between PCs.

Mixed-device parties are the part to check in game. Whether a PC player and a mobile player can drop into the same co-op match is the one thing to verify before you plan a mixed squad, and the in-game friends list is where to verify it. The Android build is also a separate store download, so confirm the mobile app listing before buying on Android. Pricing differs per platform too: the launch supporter price is $14.99 USD on Steam and $9.99 USD on mobile, and the game launches with no in-app purchases — the price and DLC page has the price actually charged today and what the optional-purchases store will hold.

Which platforms the game supports in the first place is on the cheats and platforms page.