SERIOUSLY, how many times do I have to mess up before I do it right?
In Classic Traveller, the Core Mechanic is a simple Roll 2d6 OVER your target number. These days Mongoose Traveller uses the same 2d6 Roll OVER mechanic.
HOWEVER, in Traveller 5, one must roll UNDER the target number on a variable number of d6. So many times I have to redo a character or combat because – in the moment – I automatically default to roll OVER.