Basketball and tennis are high-tech sports in the sense that they require a carefully prepared playing area and balls that bounce predictably.<p>That makes it much harder to improvise a playing field than is the case for baseball, cricket (needs a fairly small area where the ball can bounce off, and having an unpredictable bounce is considered a plus there), or, especially, soccer.<p>To play soccer, the minimum you need is an old newspaper or old rags that you shape into a ball-like form, something to tie around it to make it keep that shape, and anything that can be placed on the ground to indicate where one should imagine the goal posts to be, such as the coats of four players, marks drawn in the sand, etc.