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Clean Morse tone · optional stereo field · practice or test
idle · no account · browser-local mastery
Audio Profile
Optional stereo field (headphones) · separate from Morse tone
Morse tone is clean · centered ~550 Hz · field is optional experiment · headphones help for binaural
Anonymous organism hook: one latest hashed row per visitor (HMAC of network+agent, never raw IP). Improves defaults by learning speed, not raw accuracy. No account · no recovery · no identity desk.