Updated Carbine's, Eraser's, and Handgun's muzzleflashes.

Changed model for the Laser Arachnoid.

New particle effects for Blue Biomech's and Electric Spider's plasma projectiles.

Small changes to the second level.

Added co-op enemies to the fifth and the sixth level

1) Added a foresight to the Carbine.

2) New shaders for the Carbine, the Eraser, and the Cannon.

1) Added remastered "No Place to Hide", "Under the Iron Cloud", and "The SIlent Riddler".

2) Changed musical score: the mode now uses Serious Sam soundtracks, while Doom soundtracks were moved to the add-on.

3) Small changes to "Summer in Cairo" and "Broken Wings" to improve the flow of combat on several arenas.

4) Added the Sledgehammer with SS4 hands.

Fixed the first level not loading.

Per suggestion, I replaced the custom pistol with the SOP38 from SS4. Changed pistol's muzzleflash.

New firing sound for XL2

The first major update. Includes:

- added enemies for the cooperative game mode to all maps;

- a bunch of small fixes.