List of changes:

1. New gameplay mechanics of the Boss
   
2. Added pickable items (ammo, grenades and first aid kits), and ability to collect loot from SWAT, therefore, the ammo run out and there is no regeneration
3. Added checkpoints and the ability to load game
4. Added the ability to melee
5. There are fewer enemies but they have become more difficult
6. Some rooms have become available that were previously closed
7. A lot of small improvements and fixes