American football explained by its one core rule: four downs, ten yards

American football has a reputation for being impenetrable. It is not. There is one mechanism at its centre and every other part slots in around it: four attempts to move the ball ten yards. CHAPTERS 0:00 Four tries, ten yards 0:14 The field 0:34 The downs mechanism 1:00 The fourth-down choice 1:31 How a play works 2:01 Scoring 2:28 Why it takes three hours 2:51 That is football THE RULES, IN SHORT · 100 yards between goal lines, 10-yard end zones, 120 yards end to end, 53 1/3 yards wide · Four downs to gain 10 yards; make it and the count resets, fail and possession changes where the ball stopped · Which is why teams punt on fourth down: giving the ball up voluntarily, much further from their own end zone · Every play starts from a dead stop across the line of scrimmage, with the ball snapped back to the quarterback · The forward pass is legal and central; an incomplete pass uses up the down and the ball returns to the start of the play · Touchdown 6, kick after 1, two-point conversion 2, field goal 3, safety 2 to the defence · Four 15-minute quarters, but the clock stops constantly — 60 minutes of clock takes about three hours Figures per NFL rules. The short version is also on the channel.