multiplyAll(property, amount, checkAlive, checkVisible)
Multiplies the given property by the amount on all children in this group. Group.multiplyAll('x', 2) will x2 the child.x value for each child.
Parameters
Name Type Description property string The property to multiply, for example 'body.velocity.x' or 'angle'. amount number The amount to multiply the property by. If child.x = 10 then multiplyAll('x', 2) would make child.x = 20. checkAlive boolean If true the property will only be c