Climbing and Diving

For battles involving three dimensions, each creature or vehicle has an altitude (when flying) or depth (underwater). For air or sea battles, at least one of the creatures or vehicles should start at an altitude/depth of 0, and a new 0 level can be established at any time, to simplify play, by adjusting the altitudes of each creature or vehicle. A winged flier can gain up to 10' of altitude after moving forward by the distance shown for its maneuverability class, and can dive (lose altitude in a controlled fashion) at up to twice the normal movement rate; if the creature does not move horizontally by at least one-third its normal speed, it will stall, being forced to dive at maximum rate for one round. Floating creatures or vehicles (balloons, fly spell, flying carpets, etc.) can climb vertically without horizontal motion up to half the normal movement rate, but such "floaters" can only descend at the normal movement rate, unless they have lost the ability to float entirely.