As the capsule thunders downwards, it ejects ballast blocks to move its centre of gravity and tilt its angle of attack.

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Aim the wave at the centre of the droplet, but at an angle, and the forces generated will cause the droplet to roll.

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Centre-back Antar Yahia settled the contest with a stunning first-half volley at an angle eight yards out from Karim Ziani's punt into the box.

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