Move a player with DEVICEORIENTATION.FACEUP

I am new to unity and developing the Roll-a-Ball tutorial provided game. It works fine on Desktop and Mobile Devices , but there's an issue for moving the player regarding the device orientation. The game works fine if the Mobile device is Portrait oriented. But how to move the player accordingly if Mobile devices are oriented with Screen faced up. Also explain what does compensating sensors mean. Would be a great help.