Forgive me if I'm the last person to learn this, but I was looking through the 2014 Mazda3 service manual and came upon the valve train section and was fairly gobsmacked by how ingenious the design is. First, it has roller cam followers, which isn't much of a surprise given that it is a low-friction engine, but the cam follower has a third-class lever arrangement similar to the 14,000rpm BMW S1000RR. At the fulcrum is the showpiece: a hydraulic lash adjuster! I've seen HLAs on OHV engines, of course, and I even had HLAs on my DOHC Suzuki Swift GTi engine many years ago, but those adjusters were part of the un-sprung weight of the valve train. In Mazda's design the HLAs are fixed and don't move--thus they always maintain 0.0mm valve lash under all conditions, never need adjustment, and don't limit rpm by being part of the un-sprung weight. How cool is that?!