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azrael4h: As title. I'm using a Logitech controller , Mint 17.3. Controller works fine in other games, including Freedom Planet and Shovel Knight. So it's not the controller itself, or the USB port. Dex simply refuses to detect it, either in the included Config program or in the in-game options screen.

*Edit 1* I rebooted my system, leaving the controller hooked up. Still refuses to detect it. Dex does work, but I am not playing any platformer with a keyboard/mouse. I'm also not buying another controller just for 1 game.
Does your controller have a switch where you can switch from DirectInput mode to XInput mode?