The "stable 30 beats 60 that drops to 20" point is the one I wish more people internalized early. Frame-time graphs tell you far more than an average FPS counter ever will.

Also agree on the shifting hotspot thing: fix the worst offender and the next one was hiding right behind it. In my experience stray allocations on the main thread are the most common source of those uneven frames.

Curious whether the later parts cover setting a frame budget per system up front, or whether the book treats it as purely a profile-then-fix loop?