in RetroArch Menu (when in game, press Hotkey + B ) you can remap buttons under "Settings" (you have to press A once, to see "Settings"), "Input", "Input User 1 Binds".
But if you go out of the game (by pressing Hotkey + Start) and start the game again, the settings are lost.
I do not know how to save the remap-settings permanently (i tried several options in the RetroArch Menu like "User 1 Save Autoconfig" or "Save Configuration on Exit", or "Save Core Overrides").
