Ontario professor says he’s cracked the code for winning Tim Hortons' Roll Up the Rim to Win
... In the traditional contest where each cup has a prize printed on it, it didn't matter how many people bought cups, Wallace explains—players always had the same odds of winning.
With the digital rolling system, though, that wasn't the case. Instead of being available the moment you bought the cup, the digital prizes are only available the moment you play your roll.
"They pulled this off by distributing the prizes across the contest period into things called 'winning timeframes,'" Wallace explains.
"These were short intervals of time (0.1-1 second) during which a prize was available to be claimed. If you were the first player to tap the screen during that window, you won the prize. If no-one tapped the screen during the window, the prize went unclaimed."
He says when he read the rules of the game, he found that an unclaimed prize wouldn't be lost: it would be re-randomized for another time later in the game.
An unclaimed prize would get assigned a new winning timeframe until somebody won it...