Manipulate[
Graphics[Polygon[CirclePoints[r,n]],PlotRange->1],
{r,.5,1},
{n,3,24}
]

Manipulate[
Graphics[Polygon[CirclePoints[r,n]],PlotRange->1],
"Y"->{r,.5,1},
"X"->{n,3,24}
]

ControllerManipulate[
Graphics[Polygon[CirclePoints[r,n]],PlotRange->1],
{r,.5,1},
{n,3,24}
]