One team stands on the left side, the other on the right side.
Two guys from the blue team gets ready for two on one attack.
On the other side of the court stands one defender ready to defends those two attackers.

They passes...

When the LAST blue PLAYER (not ball) crosses the half court line. Red player two runs through the middle circle to help his teammate(red1)

Red player 2 will force the two attackers to finish their attack as soon as possible, to prevent the situation to become two on two instead of two on one.

While the attack is continuing blue player 3 (defender now) is getting ready for red offense.

After the blue team shoots, the red team gets the ball and starts the attack on the opposite basket

again, when the last player crosses the middle line, blue player 4 runs through the middle circle.

Red team attacks, forced to score as fast as they can.

Everything now repeats, so all players get a chance to attack and to defend.