Valve has announced a massive new update for Left 4 Dead 2.

The fan-made update, now officially released as canon, includes a brand new campaign based on the original survival map, however now it’s no longer impossible to escape. There’s now a path to escape through the lighthouse, through hordes of zombies.

To celebrate the new update, Left 4 Dead 2 is free to play this weekend on Windows PC (via Steam), and is also 80% off if you just want to finally purchase it outright.

Here’s a new trailer on the update:

Here’s a rundown on the new update:

Take a Stand in This Massive Community-Made Update

Years in the making, The Last Stand is a massive Left 4 Dead 2 update created entirely by the L4D community. Find your friends, dust off your guns, and face the zombie horde one last time in over twenty new Survival Arenas, four Scavenge Arenas and a Campaign based on The Lighthouse Survival map.

New achievements, melee weapons, animations, dialog, competitive balance adjustments and other surprises await anyone brave enough to take a stand.

DEATH IS NO LONGER THE ONLY OPTION
The Last Stand Expanded Campaign
The Last Stand is a brand new campaign based on the original Survival map—it’s no longer impossible to escape. But it won’t be easy. Originally a no-win death trap, the lighthouse now offers a path to salvation. Unfortunately, it’s directly through hordes of bloodthirsty infected.

TRY TO SURVIVE
26 New Survival Maps
How long can you withstand the onslaught of the undead in 26 all-new environments?

FUEL CRISIS
Get Gassed in Four New Scavenge Arenas
When a generator is your lifeline, the gas prices can truly skyrocket. Outlast your opponents by scavenging for fuel, or be overwhelmed by the horde.

A PITCHED BATTLE
Plus a Shoveled Battle
Introducing the shovel and pitchfork—these centuries-old farming technologies make their proud debut on the zombie killing fields as all-new melee weapons.