ShowPlay Reference Manual, Chapter 3 (ControlVariables): sy0
SY0 is an integer number – its default value is 1/2 the screen width.
Showplay will use SY0 as the horizontal center pixel position for all visual stimuli that are to be centered in the display.
See Also:
Display Scaling,
Widscale,
Hgtscale,
RGBscale,
Sx0
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