Some fortified themselves by wearing goggles and using dining hall trays as shields. Others attempted to intimidate by waving skull and crossbones flags. Colin Griffin went shirtless. No matter the approach, thousands of University of Wisconsin-Madison students took advantage of an unplanned day off and hurled snowballs at one another Wednesday in a massive melee. Classes had been canceled due to more than a foot of snow and blizzard-like conditions that brought sub-freezing temperatures and winds of more than 20 miles per hour.