From IGN.
"Top Spin 4's gameplay is taking a slightly different approach than in previous years. For starters, there is now a three-tiered meter underneath your player that builds as you wind up for a shot. The more the meter builds, the harder and more accurate your shot will be. Of course, the pace and placement is also dependent on your ability to release the shot button (A for flat spin, B for top spin, X for slice and Y for lob) at the proper time in the animation. Failing to do so will yield a limp return and an easy put-away for your opponent."
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