Few seasonal activities are as universal — across time, place, or culture — as the snowball fight. As many of us head into the cold, winter months, hoping for a holiday season with frosted trees or icicles dripping like stalactites from the eaves of homes, we might also long for that slightly slushy grade of powder that makes for perfect packing. Snowmen and angels can be created later. And perhaps there will be sledding: on toboggans (for connoisseurs) or cafeteria trays (for the crafty). Yet nothing signals the year’s first snowfall quite like an apple-sized projectile cutting a parabolic path — through crisp evening air, the haloed light of streetlamps, and exhalations of foggy, illuminated breath — to make direct contact with an unsuspecting hat or coat.