Beta O.2 available now for Windows with lots of improvements and bug fixes: 

-Tutorial level

-Voices for Bonus and UI,

-Helicopter Extraction

-Hold button buy reduced,

- Coop: 

End of Wave Reanimation is automatic if the 1st player is still alive, 

Price for reanimation have changed(400 instead of 200),

Red blood and bug fixes,

 Cheers!