Heartline vs centerline rotation
Where the train rotates changes how inversions feel in your head and gut.
Track is a tube in space; trains can roll around different axes. Centerline rotation spins around the middle of the track — your head travels a bigger circle than your seat.
Heartline (or heartline roll) elements try to rotate around roughly chest height, reducing neck whip.
Wing and inverted coasters exaggerate offset paths — clearance dives and near-miss wood rely on rotating around a chosen axis.
POV alone rarely shows which axis a designer picked; your body tells you on the first inversion.