Zombie Panic! was an old prototype survival-horror cooperative Half-Life 1 modification, first released back on Oct 31, 2004 via ModDB and now re-released officially on Steam for free!

Following the classic human vs. zombie concept, the game pits a group of survivors against the walking dead. Your goal is to complete a number of objectives to reach safety, or take out the remaining zombies still lingering in the area. But those who were once your friends after death become the very same creatures you're trying to escape.

Ammo is a scarce resource, so don't run around guns blazing or you'll run out of ammo fast and be easy prey. The more weapons and ammo you carry, the slower you move, so sharing what you don't need with your teammates increases your chance of survival.

The Steam version features:

• Half-Life's 25th anniversary support

• Steam Achievements and Workshop

• New fatigue system, replacing the 'jump delay'

• New Zombie vision and ammobank HUD inventory

• New first-person and third-peson animations

• New player models and weapons

• New mapping entities-tools

• Updated User Interface

• Updated classic maps visuals and gameplay

• Rewritten source code using 'BugfixedHL' as a base

• And much more!

We've also uploaded the source code to GitHub, making ZP1 opensourced!

All credits to the original Zombie Panic! team who initially made this prototype in 2004.