A_FlickyFly is an action that makes the actor fly in a direction. Var1 sets the speed at which the actor moves. Var2 determines how far ahead the target should be considered from the actor's location.
Code – A_FlickyFly
// Function: A_FlickyFly
// Description: Flicky flying function.
// var1 = how fast to fly
// var2 = how far ahead the target should be considered
void A_FlickyFly(mobj_t *actor)
INT32 locvar1 = var1;
INT32 locvar2 = var2;
if (LUA_CallAction(A_FLICKYFLY, actor))
P_InternalFlickyFly(actor, locvar1, locvar2,
FINECOSINE((((actor->fuse % 36) * ANG10) >> ANGLETOFINESHIFT) & FINEMASK)