  I review recent developments in QCD thermodynamics and collective excitations
from the hard-thermal-loop effective theory. I begin by motivating the
discussion with open questions from heavy-ion collisions. I then discuss a
finite-temperature and -density calculation of QCD thermodynamics at NNLO from
the hard-thermal-loop perturbation theory. Finally I discuss a recent
exploration of generalizing the hard-thermal-loop framework to the
(chromo)magnetic scale $g^2T$, from which a novel massless mode is uncovered.
