The following are rules regarding the offensive side of the ball.
Offenses are allowed 35 seconds from the time the ball is spotted back at the LOS. The defense is responsible for spotting the ball and then keeping track of the time -- counting out loud as the time gets to ten seconds ("ten, nine, eight, seven... etc.").Once the offense breaks the huddle the play clock is stopped.
If the offense stays in the huddle after the 35 seconds, a "delay of game" penalty will be enforced and the ball will be moved back 4 paces.
Note: Offenses can't re-huddle.
Only 5 offensive players besides the quarterback may be eligible to catch a forward pass beyond the line of scrimmage. If teams have seven a side, the center is automatically ineligible. If more than seven a side, the center and one lineman (lineperson, sorry) is ineligible (etc.)
INELIGIBLE PLAYERS MUST LINE UP ON THE LINE OF SCRIMMAGE ADJACENT TO EACH OTHER AND ON THE LINE OF SCRIMMAGE.
Even with six players or less on a team, a team with one extra player must have an ineligible center who cannot catch a forward pass.
INELIGIBLE" LINEMEN CAN RECEIVE A BACKWARDS PASS OR A "BACKWARDS MOVING" HANDOFF.
"INELIGIBLE" LINEMEN CAN ALSO RECEIVE A FORWARD PASS OR A "FORWARD MOVING" HANDOFF FROM BEHIND THE LINE OF SCRIMMAGE, BUT ONLY AFTER THE DEFENSE CROSSES THE LINE OF SCRIMMAGE (i.e. after "Four Mississippi", a Blitz, or after a muffed snap or a fumble.)
Ineligibles should raise their hand as they approach the line so the defense can identify them before the ball is snapped.
There are no rules regarding number of players in motion; number of players on the line vs offset etc.
Note: Offenses can't re-huddle. Once the huddle has been broken there can be no re-huddle.
Running plays are legal. Note: when the offense blocks downfield or when the quarterback (the player who receives the snap) gives the ball to a teammate (via a handoff, lateral, or forward pass), the defense can rush past the line of scrimmage to tag the ball carrier without waiting to count to "4 Mississippi".
Blocking is allowed from below the neck to above the waist ("within the frame"). NO cut blocks allowed; no shoulder blocking; no blocking below the waist.
As per regular football rules, downfield blocking before the ball leaves the quarterback's hand as a forward pass is a penalty.
Ineligible linemen can move downfield but will be considered illegally downfield if the they move across the line of scrimmage before a forward pass does. They can move downfield if the forward pass never crosses the neutral zone though (e.g. a screen pass).
Downfield blocking immediately negates the Four Mississippi count.
Any number of forward passes are allowed from behind the line of scrimmage. (Exception: a player cannot pass to himself/herself.) Once past the line of scrimmage, only backward passes are allowed. (Backward passes are allowed from any player to any player at any time, including "ineligible" linemen.)
An incomplete forward pass behind the line of scrimmage is considered a dead ball, an incomplete backwards pass, including a muffed snap, is a live ball.
The ball must be snapped from the ground, (not from a standing position.) Any "double clutching" is considered an illegal snap.
If the quarterback is directly under center (for a direct snap), defenders cannot reach across the line of scrimmage for a tag, even on a blitz.
Fumbles are live balls and can be recovered by either team. In the interests of safety it becomes the responsibility of players not involved in the pile to quickly determine who has recovered the fumble and to then stop play as soon as possible. As per regular football rules, joint-possesion of a fumble (or pass) is awarded to the offense.