Full Controller Support!

I just updated the in-game settings screen to work with Steam and XBox 360/One controllers. Now instead of needing a mouse to click the settings buttons, you can select them with the left joystick or d-pad, and click them with the A button. Also updated the game to work with every Xbox/Steam controller that's plugged in, and not just the first one it sees. Up until now only one controller would be recognized by the game if more than one were plugged in. Also added support for using the D-Pad on controllers, which should make the faster levels a lot easier because you can change direction much quicker with the D-Pad than you can using the joystick.