on my mobile (galaxy grand) the known/unknown buttons are off screen even for one line questions and answers
in the beginning, the buttons were on the bottom on small screens, so I could press them in the same spot no matter what the card was like. this got lost along the way but I consider it pretty important for effective learning.
This is only for mobile. on the big screen, it may be as is now as one can use hot keys that don't move neither.
Bug is accepted as 'minor ' and the Team needs to fix it for Release beta 1.