Schematic outlining the Hoeflich et al. (2021) off-center DDT explosion model of a M_Ch-mass C + O WD. Initially, centrally located C + O burning initiates a deflagration flame front, which due to the high central density of the WD, produces an inner, spherical region of electron capture (EC) elements (depicted by filled cyan circle) consisting mostly of stable Fe-group elements. The EC region lays within a spherical shell of remaining deflagration ash consisting mainly of radioactive ⁵⁶Ni (green ring). After consuming 0.3 M_⊙ of the WD and the leading edge of the deflagration flame front reaches ρ_tr, a ∼2000 km s⁻¹ off-center DDT is triggered (black point). As the DDT occurs on a moving background, the detonation burning front requires time to reach and fully consume the remaining C + O ejecta. As a result, the detonation burning products are distributed asymmetrically, and as depicted in the schematic by the intensity of yellow which reflects the abundance mass fraction of ⁵⁶Ni, the majority of the ⁵⁶Ni produced during the detonation burning phase is distributed in a banana shape region with a ring surrounding the deflagration burning ash and along a positive viewing angle relative to the equator. Depending on the viewing angle, nebular emission lines will appear blue- or red-shifted.