ThrustThingZ

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128:ThrustThingZ(tid, speed, up/down, add/set)

tid: Thing ID of the thing to thrust.  If 0, it'll thrust the activator
     (usually the player).
force: The force, in units per tic (1 second = 35 tics) divided by 4,
       to apply to the thing.
up/down: The direction to thrust the thing. (0 = up, 1 = down)
set/add: If 0, sets the thing's vertical speed to 0 and only then applies
         the force. If 1, adds the speed resulting from the special's force
         to the thing's current vertical speed.

Thrusts the thing vertically, given the specified force. It can either apply the force to the thing's current vertical speed or it can set the thing's vertical speed to 0 before applying the force. Can easily be combined with ThrustThing.