Players take turns finding the secret number on a number line. In each round, the computer designates a secret number on a number line. Players try to guess this secret number by clicking one of the numbers. If the number chosen is larger than the secret number, that number and all larger numbers on the number line are hidden by the train. If the number chosen is smaller than the secret number, that number and all smaller numbers on the number line are hidden by the train. Players take turns clicking numbers until one of them identifies the secret number and wins the round.