Change is a constant of Formula 1. Across the two pre-season tests, there have been plenty of updates and new additions to dissect on the surgeon's table, as the trackside engineers carefully analyse their designs' benefits, determine whether they operate as they should or whether more work is needed.
And in the past, teams with less resource have had to roll out the previous year's car for one last time, making the requisite modifications and using it as a test mule before the actual car hits the road.
But rarely has a top team launched a new car, milked it for all it's worth, and then turned up for the second week with a completely revised package. Reigning champion team Mercedes, with its W10, has done just that - and, quite understandably, it raises quite a few questions.