how you make an separate air file? only one is allowed.
also it is very simple to do that.
See this(short version)
;---------------------------------------------------------------------------
; RUN_BACK
[statedef 105]
type = A
physics = A
anim = 105
ctrl = 0
[state 105, 1]
type = VelSet
trigger1 = 1
x = const(velocity.run.back.x)
y = 0
[state 105, 2]
type = veladd
trigger1 = time > 0
x = -1
y = -0.4
[state 105, 3]
type = posset
trigger1 = pos y != 0
y = 0
[state 105, 2]
type = veladd
trigger1 = time > 0
x = -2
y = -0.4
[state 105, 2]
type = veladd
trigger1 = time > 0
x = -2
y = -0.4
[state 100, 2] ;Prevent run from canceling into walk
type = AssertSpecial
trigger1 = 1
flag = NoWalk
[state 105, 3]
type = ChangeState
trigger1 = command != "holdback"
value = 0