The 2D turtle had a position and one angle. The 3D turtle carries a full
frame: three arrows at right angles — Heading (where it's going),
Left, and Up — like an aeroplane.
Each rotation symbol spins the frame around one of those arrows:
+/- yaw around Up,
&/^ pitch around Left,
\// roll around Heading.
Roll is the new trick: it costs nothing visually by itself, but it decides
which way the next pitch or yaw bends — that's how a single rule like
[&P]/[&P]/[&P] plants petals in a whorl around the stem.
Two drawing symbols grow organs instead of lines: P sprouts a
parametric petal (a small curved surface, shaded like a checkerboard) and
L a leaf. Their shape comes from the Petal sliders, their
direction from the turtle's frame at that moment.