The main task of the initial period of studying physics is inculcating the interest and enthusiasm of children in this subject. The root cause of all interest is surprise, and for children there is almost nothing more surprising than a new and unusual toy. There is a whole class of toys with unusual mechanisms, behaviour, or way of interacting with them. Having explained to the child the not quite ordinary, and often paradoxical, properties of such toys, we can gradually instil in him an i...