subAll(property, amount, checkAlive, checkVisible)
Subtracts the amount from the given property on all children in this group. Group.subAll('x', 10) will minus 10 from the child.x value for each child.
Parameters
Name Type Description property string The property to decrement, for example 'body.velocity.x' or 'angle'. amount number The amount to subtract from the property. If child.x = 50 then subAll('x', 40) would make child.x = 10. checkAlive boolean If true the property will only be