Major Update

Remote Co-op Mode: Play Boxhead: Immortal remotely with your friends! Use the "Multiplayer" button to create a room, and then invite your Steam friends to join the battlefield.
Friendly Fire Protection Mechanism: When friendly fire is enabled, firearms will only cause 40% damage to teammates. Additionally, for each challenge mode selected, damage to teammates increases by 20% (e.g., if all 4 challenge modes are chosen, damage to teammates will be 120%).

Adjustment to Support Active Skill 3 (bombardment): Small-scale bombardments have been removed. Instead, each bombardment generates ashes, dealing a larger area-of-effect attack to monsters, dealing 20% bombardment DMG. Additionally, affected monsters will suffer continuous bleeding (losing 40 HP every 1s or 4% max HP, whichever is higher, for 5s).
Weapon Upgrade Adjustments:
- Pistol “Lightweighting”: Mobility increased by 25%, and movement SPD increased by 25% → Mobility increased by 40%, and movement SPD increased by 10%
- SMG:
  - “Polymer Modification”: Mobility increased by 25%, and movement SPD increased by 25% → Mobility increased by 40%, and movement SPD increased by 10%
  - “Special Ammunition”: blast radius: 2m → 2.5m, DMG: 80% → 50%
- Rifle “Lightweight Handguard”: Mobility increased by 15%, and movement SPD increased by 15% → Mobility increased by 40%, and movement SPD increased by 10%
by 10% (previously 15% each).
Adjusted Monster HP Enhancement Mechanism and Explanation: When there are more than one player in the game, each additional player increases zombie max HP by 50%. This enhancement is independent of the “2x Monster Health” challenge mode.
Performance Optimization.
Optimized some sound effects.