Updates to Sanctum have been released. The updates will be applied automatically when your Steam client is restarted. The major changes include:

Sanctum

• Added support for 4 players in co-op!
  
• Added Endless Singleplayer mode!
  
• Added Limited amount of waves in multiplayer!
  
• Added Turbo Mode!
  
• Added more Achievements!
  
• Added co-op build and upgrade towers!
  
• Added Ping in Server Browser
  
• Added option for server to kick players
  
• Added option to see full games in Server Browser
  
• New and improved HUD arrows!
  
• Improved GamePad support!
  
• You can now "Ping" by right clicking in the overview!
  

On top of this, a huge amount of general bug fixes, performance optimization and balance changes has been made.