The introduction of Windows 8, the emergence of touchscreens and the increasing efficiency of components have helped laptops get thinner and lighter, and they're also behind the growth of hybrids ? machines designed for use as both notebooks and tablets. The HP Envy 15 x360 (model 15-u000na) is one such system. It flips between laptop and tablet modes with a hinge that rotates through 360 degrees, and its 15.6-inch screen makes it one of the biggest hybrids we've seen.Turning headsThe Envy's 5.3 pound weight (2.4kg) and 0.94-inch thickness (about 24mm) are more akin to laptops than tablets, and that stands up when the HP is compared to its rivals: the Lenovo Flex 2 15 is another 15.6-inch hybrid, but it's thinner and lighter. The HP's nearest laptop competitor, the Dell Inspiron 15 7000, is only a little bigger.