[Moo] FX is not defined

[dmidz]

Hello,
Am I dumb or what, if I use Element.tween(options), it works well, if
I try instancing a new FX like at the doc, or a FX.Tween :
http://mootools.net/docs/core/Fx/Fx.Tween#Fx-Tween:constructor
it just fails, if I log FX : it is undefined, please have a look at
this simple jsfiddle : http://jsfiddle.net/qvrNj/1/
What I am doing wrong ?! thanks for any help...