Safe Cracker uses Timed Play.
At the beginning of a player's game, he is given a set amount of time. It is stated as "minutes", but it is translated roughly into seconds of gameplay. The default start time is 45 minutes, but I have mine set to 55 minutes. The time is counted down on the timer in the middle of the playfield (shown on the right), and also as a diminishing progress bar on the DMD display.
When time runs out, the player is in "Sudden Death", which means the game ends when the ball drains next, unless the player can manage to earn extra time. During normal gameplay, time can be added in a number of ways, which will be detailed as I go along.
To be continued...