The level bar is his mouth. If it moves, he is speaking with your voice. Your voice is analysed only — it never plays through the speakers, so it cannot echo. Your students hear you through your normal Zoom microphone.
Write on the board with a stylus, trackpad or mouse — his hand follows your pen in real time.
Load one portrait — head and shoulders, like a museum painting. It becomes the teacher: edges softened into the room, head turning as you speak, a chalk arm reaching to the board, and a mouth that moves with your voice.
Transparent PNGs, each part on its own file. The rig moves them: the arm follows your pen, the head turns, the mouth swaps on your voice.
Pick a voice style, then Hear 12s to preview. Render lesson writes out a single video file with that voice on it. Rendering runs at playback speed, so a ten minute lesson takes about ten minutes — leave the tab open. Any student questions you marked with Q are voiced separately. Everything happens in your browser; nothing leaves your machine.
Press Q to hand the floor to a student. Speak the question yourself, then press Q again to return to the figure and answer. Works mid-lesson and while recording.