Myself and a group of friends are visiting Lisbon in a couple of weeks time. After some research, it seems that a zapping Viva Viagem card will be our best transport option as we would like to use most of the forms of transport at some point including the train to Sintra. Am I right in thinking the train is covered on the zapping mode? And what about ferries?We also like doing most of our exploring on foot so don't want to pay each day for a daily card that we might not use. Bearing in mind the trip to Sintra, what would be a reasonable amount to load onto the card, can it be topped up easily, and is there a way of finding out how much value is left on it ( to ensure that there is enough to pay for where we want to go!)?