Pile Up was designed to be a compulsive match-4 where players have to sort packages into their corresponding delivery truck. Players are awarded 100 points on matching crates with trucks. On mismatches or expired boxes, players lose time. At 4 positive matches, players receive a bonus 1000 points and time, the full truck leaves, and a new truck drives in. This is where the tension of the game comes from - the player is relatively quick and can match objects easily. If there was a wrong match, it would most likely be from an input error rather than confusion. By design, this balance and reward structure allows a skilled player to play the game in perpetuity, raking in time with fullloads. But this quick-fire, constant matching means when they're receiving packages for trucks they can't match, they're eagerly waiting, painfully even, for a matching color to finish a combo and get a new truck to clear their stack of packages and keep the timer going. By keeping the pace high, and making players beg for the right crate, players would be clearing trucks quicker and quicker, and eventually get to a point where they start making errors.