Using blocks for user validation

  def get_validated_user_input
  while true
    input = get_user_input
    break if yield(input)
    print_invalid_message
  end
  input
end

user_move = get_validated_user_input {|input| move_valid?(input, board)}
board_size = get_validated_user_input {|input| board_size_valid?(input, board_size_options)}