may b something was wrong previously. now it is correct.
can't fall over boundary. must jump to empty cell. and only black cells. however, u must check - new checker may attack or be attacked :P

Yes, it is somehow strange but if one of players put checker and this checker can attack the checker of another colour, so the game is stopped with the fool (!) of this player.
Naturally, if this put checker could be attacked the end is the same.