The Vircon32: C API reference page may be helpful - http://www.vircon32.com/api.html

There is obviously your arrow key inputs but there are other buttons available as well. At least for gamepad(0) we have button_?_ = ? for the average keyboard:

• A = X
• B = Z
• X = S
• Y = A
• L = W
• R = W
• Start = Enter Key

These probably aren't needed but are here incase.