Frame 1 -- David's spine tilts slightly away from the target, setting up a powerful coil. Notice how his left foot is flared out, which helps him clear out his left side on the forward swing.
Frame 2 -- Duval makes a fairly wide extension on the takeaway, but not so much as to sway off the ball.
Frame 3 -- David has maintained his center beautifully, keeping his body weight between his insteps. He's fully coiled and ready to unleash the downswing.
Frame 4 -- From the top, he shifts to the left and starts rotating his chest, harnessing the power of his wrist hinge until just before impact.
Frame 5 -- After the ball is struck, his arms go their widest, as the clubhead "chases" the ball. His unique head swivel tells the story: He's so front-side oriented, his eyes are out in front before impact.
Frame 6 -- This picture is worth a thousand words. His upper body is perfectly vertical over his left foot, indicating a complete weight transfer and a level turn through impact. Notice also that his chest is facing well left of the target -- almost opposite of address -- and his hands are low and around his neck, a result of the powerful chasing of the clubhead after the ball.