players on the line cannot be in motion. In Canadian football, all offensive backfield players, except the quarterback, may be in motion at the snap; players in motion may move in any direction as long as they are behind the line of scrimmage at the snap. In addition, the two players on the ends of the line of scrimmage (generally wide receivers) may also be in motion along the line. Many teams encourage this unlimited motion, as it can confuse the defence. It also provides receivers the advantage of a running start, as they can time their runs so that they cross the line of scrimmage at speed when the ball is snapped, allowing them to get downfield faster than receivers in American football, allowing for comparatively longer throws in the same amount of time after the snap or quicker throws for a given distance. Time rules In American football, the offensive team must run a play within 25 seconds of the referee whistling the play in – except in the NCAA (college) and the NFL where teams have 40 seconds from the end of the previous play, or 25 seconds following a penalty or timeout. In Canadian football (at all levels of play), teams have 20 seconds after the play is whistled in regardless of the preceding situation. American football rules allow each team to have three timeouts in each half, and the NFL stops play for a "two-minute warning". However, NCAA football has no two-minute warning, but the clock stops on a first down until the ball is ready for play if the play ended in the field of play. In the CFL, each team has two time-outs a game, but cannot use both in the last three minutes of the game, while at lower levels of Canadian football, each team has two. Canadian football has a three-minute rather than a two-minute warning. Also, at all levels of Canadian football, the clock is stopped after every play during the last three minutes of each half. Once the referee has set the ball, the clock restarts if the last play ended with a runner tackled in the field of play. Timing rules change drastically after the minutes warning in both leagues: In American football, the clock continues to run after any tackle in bounds, but stops after an incomplete pass or a tackle out of bounds. If the clock