Topspin, Flat, Slice — the Shape of Your Shots.
The gyroscope on your Watch doesn't measure the ball directly — but the wrist rotation at impact is a tight proxy for the type of contact you're making. CourtsidePlay translates that rotation into a shot-shape breakdown.
A donut chart of your spin signature
The Spin Distribution card shows what percentage of your classified shots rolled up (topspin), went through (flat), or cut under (slice). In our 77-shot demo: 89% topspin, 9% flat, 1% slice.
How is spin estimated?
At the moment of impact, CourtsidePlay looks at two signals on the gyroscope: the direction of wrist rotation (up-over-the-ball versus under-the-ball versus neutral-through-the-ball) and its magnitude relative to the swing speed. These two numbers map to topspin, slice, or flat with useful accuracy — especially on groundstrokes.
- Not a direct measurement of spin RPM — it's a shape estimate from wrist motion.
- Most useful for tracking trends across many matches (e.g. slice rate going up under pressure).
- Only classified shots count; serves are excluded from the distribution since they're overhead impacts.
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