  We calculate the mass spectrum and the structure of the positronium system at
a strong coupling in a basis light-front approach. We start from the
light-front QED Hamiltonian and retain one dynamical photon in our basis. We
perform the fermion mass renormalization associated with the nonperturbative
fermion self-energy correction. We present the resulting mass spectrum and wave
functions for the selected low-lying states. Next, we apply this approach to
QCD and calculate the heavy meson system with one dynamical gluon retained. We
illustrate the obtained mass spectrum and wave functions for the selected
low-lying states.
