font-display: swapNo invisible text during font load — layout stable from first paint

contain: layout styleEach chapter/section is paint-isolated — siblings don't reflow

content-visibility: autoOff-screen sections skipped until scroll — saves parse + layout time

prefers-reduced-motionAll animation durations collapse to 1ms for users who need it

preconnect + preloadFont DNS + TLS handshake started before parser hits the link tag

solid nav backgroundbackdrop-filter removed — saves ~8ms/frame on scroll repaint

passive scroll listenerProgress bar scroll handler registered passive — never blocks input

GPU-only animationsAll transitions use opacity + transform only — compositor thread, zero layout