Airship fold
z(n+1) = (absolute x(n) + i times x(n) times absolute y(n))^2 + c
Fold the real component with an absolute value, then square the complex number (|xₙ| + i·xₙ·|yₙ|) before adding c. In expanded form, the real part after squaring is xₙ₊₁ = (|xₙ|)² − (xₙ·|yₙ|)² + Re(c), while the imaginary part is yₙ₊₁ = 2·|xₙ|·xₙ·|yₙ| + Im(c). Notice that xₙ appears in the cross term both inside and outside the absolute value. Its sign therefore travels through the iteration.
Try c = i. For the Burning Ship, the orbit diverges quickly. For the Airship, z₁ = (|0| + i·0·|0|)² + i = i, z₂ = (|0| + i·0·|1|)² + i = i, and the orbit remains bounded at i indefinitely — a fixed point that the Burning Ship does not share. The asymmetric fold can therefore stabilize or destabilize orbits that behave identically in the Mandelbrot set.
