private void DrawSpinner(float cx, float cy, float r, float t)
{
float a0 = 0.0f + t * 6.0f;
float a1 = MathF.PI + t * 6.0f;
float r0 = r;
float r1 = r * 0.75f;
_nvg.Save();
_nvg.BeginPath();
_nvg.Arc(cx, cy, r0, a0, a1, Winding.Cw);
_nvg.Arc(cx, cy, r1, a1, a0, Winding.Ccw);
_nvg.ClosePath();
float ax = cx + MathF.Cos(a0) * (r0 + r1) * 0.5f;
float ay = cy + MathF.Sin(a0) * (r0 + r1) * 0.5f;
float bx = cx + MathF.Cos(a0) * (r0 + r1) * 0.5f;
float by = cy + MathF.Sin(a0) * (r0 + r1) * 0.5f;
Paint paint = _nvg.LinearGradient(ax, ay, bx, by, _nvg.Rgba(0, 0, 0, 0), _nvg.Rgba(0, 0, 0, 128));
_nvg.FillPaint(paint);
_nvg.Fill();
_nvg.Restore();
}