Added:
6 new music tracks.
Replaced music in the main menu.

Added level system.
-When you kill bots, you will receive experience that will increase your characteristics.

The easy difficulty level has been reworked.
-Reduced HP of some bots

Reworked HUD
-Added level display
-Added numerical display of HP amount
-Added Timer. So you can brag to your friends that you were able to hold out for more than a minute
-Changed HUD color for better perception