Subscribe to download
Gian's Splitscreen Menu

Be sure to go to Steam's Big Picture, Settings, Controller Settings and check [your controller] Configuration Support. Also be sure to have your controller input layout correctly.
In-game, enable Gamepad in Keyboard/Mouse settings.
To play custom mutations online, they'll have to be played via a Local Server.

Useful console commands (replace brackets with values):

1. To play custom campaigns
   
   map [mapname]; wait 100; connect_splitscreen localhost 2
2. To get every mapname you have installed
   
   maps *
3. To change character in game (needs sv_cheats 1)
   
   sb_takecontrol [name]
4. To change character in game (first go idle)
   
   jointeam 2 [name]
   For player two add cmd2 before the command.

Helpful guides:
How to play splitscreen LAN/online.
How to play splitscreen with two monitors.
How to play splitscreen in official servers.

Cutom (minimalistic) menu. Nothing is removed, just relocated.

Menu contains:

• SFKTeam's Splitscreen menu (language compatibility, keyboard/gamepad navigation and more fixes).
  
• Mutation expansion made by the community (mostly Rayman1103) and me.
  
• In-game Extras submenu with X360 controller settings.
  
• Developer Console Button (in extras).
  
• Server Browser Button (in extras).
  
• Addons custom menu by me.