Ishac Bertran’s "Pas a Pas" teaches geometry to four-year-olds with a bit of stop-motion magic--no complex editing software required. For all the educational potential of tablets and low-cost laptops, there’s still a strong case for giving youngsters actual, physical stuff to play with. Give a child an iPad app and you educate him for an hour; give a child some wooden blocks and you educate him for a lifetime--that’s the way the old Chinese proverb goes, right?