inc: 0.05
a: 4
b: 3
n: 2.5
α = 0.8028514559173916 rad (slider from 0 to 6.283185307179586)
c1 = CurveCartesian(((sgn(cos(t)) * a) * abs(cos(t))^(2 / n)), ((sgn(sin(t)) * b) * abs(sin(t))^(2 / n)), 0, t, 0, (2 * π))
R: 2.5
c2 = CurveCartesian(((sgn(cos(t)) * (a + R)) * abs(cos(t))^(2 / n)), ((sgn(sin(t)) * (b + R)) * abs(sin(t))^(2 / n)), R, t, 0, (2 * π))
e = Surface(c1(t) + ((c2(t) - c1(t)) * k), t, 0, (2 * π), k, 0, 1)
a1: a - inc
c = Surface(c1(t) - (c1(t) * k), t, 0, (2 * π), k, 0, 1)
b1: b - inc
l1 = Sequence(Point[CurveCartesian[((sgn(cos(t)) * (a1 + r)) * abs(cos(t))^(2 / n)), ((sgn(sin(t)) * (b1 + r)) * abs(sin(t))^(2 / n)), r, t, 0, (2 * π)], α / ((2 * π))], r, 0, 2.5, 0.1)