An update has been released and here's the change log

Fixed

• Demo version doesn't tell the user it's a demo version
• Tutorial ambush spawner firing prematurely

Changed

• Locked level buttons are now disabled instead of being hidden
• Player collision and camera position has been adjusted a bit
• Ballistics physics are even more realistic now
• Greatly increased all firearm projectiles initial velocity
• Colt 1911 and a shotgun are now available in the demo