How many players are on the field, and how does a possession work?

NFL FLAG is 5-on-5. Substitutions can be made whenever the ball is dead.

The field is 25 yards wide and either 70 yards long with 10-yard end zones or 64 yards long with 7-yard end zones. There are no kickoffs:

1. Each possession starts at the offense's own 5-yard line.
2. The offense has 4 downs to cross midfield.
3. Once past midfield, it has 3 downs to score a touchdown.
4. If it doesn't score, the other team takes over at its own 5-yard line.

Punt or play: before a 4th down short of midfield, the referee asks the head coach to declare "punt" or "play". A "punt" gives the other team the ball at its own 5-yard line. If the offense plays and fails to cross midfield, the other team takes over where the play ended.

Every play starts with the ball spotted in the middle of the field, never closer than 10 yards to a sideline.