Zombie AI and Train Defense Improvements

The recent zombie update made them much more interesting — especially with climbing, jumping, and the sleeping mechanic. However, there are still some inconsistencies and missed opportunities that could improve both immersion and gameplay balance.
For example, zombies can jump through train windows even when they are covered with metal sheets, which breaks immersion.

Suggestions:

1. Improve zombie variety Add new zombie variants to make encounters less predictable and more engaging.
2. Special zombie variant: Armed Introduce rare zombies with weapons embedded in their bodies. When they wake up, they use these weapons to deal higher damage, creating more dangerous encounters.
3. Train entry consistency Zombies should be able to enter through all windows and from the back of the train, not just the front. In return, metal sheets should fully block entry when applied.
4. Metal sheet Metal sheets should have durability and break after taking enough damage. Zombies could attack to force their way in.

These changes would fix current inconsistencies, and make zombies even better.