Bethesda unveiled that gamers from three platforms will be able to join the Doom alpha, allowing them to test out the multiplayer gameplay of the legendary first-person shooter.

Players from PlayStation 4, Xbox One and PC can take part in the closed alpha for the Doom multiplayer, Bethesda confirmed.

The alpha started on Dec. 3, at 7 p.m. PST (10 p.m. EST) and will be ongoing until Dec. 6 at 8:59 p.m. PST (11:59 p.m. EST).

Initially, only those who preordered Wolfenstein: The New Order and signed up for access could enter the closed alpha.

Bethesda revealed on Twitter that the public request (read: pressure) for extending the alpha more than originally intended was high enough to produce results. Now, more people can sign up and enter the closed testing period, on a first-come, first-served basis.

By popular demand, we’re opening #DOOM alpha access beyond our #DOOM Beta group. Xbox, Steam, and PS4 registration links incoming.

— Bethesda Softworks (@bethesda) December 3, 2015

Before the game developer changed its mind and widened the range of the alpha, only buyers who ordered digital copies of Wolfenstein: The New Order could verify if they were eligible to join the alpha by looking in the Steam library. Xbox One customers of The New Order, meanwhile, received a code in the Xbox Live Messenger notifying them that they were selected for the closed testing period.

Details in the alpha FAQ are now available on the official site and they will guide those who bought physical copies of TNO through the slightly convoluted process. Bethesda also explained how PS4 gamers who want to join in from outside the U.S. can go about.

PS users outside the US: if you bought Wolfenstein TNO on PS3 or PS4, search for DOOM Closed Alpha on PSN. If you can DL, you're in. — Bethesda Softworks (@bethesda) December 3, 2015

There is limited content available in the alpha test: gamers can hunt each other on a single map, and the only deathmatch option involves two teams of six-versus-six fighting one another. The seven weapons are the Plasma Rifle, Repeater, Rocket Launcher, Static Cannon, Super Shotgun and Vortex Rifle, with additional strategic items such as the Frag Grenade and Personal Teleporter.

Players who join the alpha must sign a non-disclosure agreement, keeping the lid on the details they encounter.

Bethesda pointed out that the alpha is only one step toward the open beta and the final version of Doom.

You can watch the gameplay trailer below to get a sense of what is coming in the alpha.