n < 1Star / hypocycloid — concave sides, cusps at axes
n = 1Diamond — rhombus, straight sides
n = 2Ellipse — the familiar conic section
n = 2.5Squircle — Piet Hein's ideal. Used in Sergels Torg, Stockholm
n = 4Rounded rectangle — very square, softly cornered
n → ∞Rectangle — sides flatten to straight lines