Carefree by Kevin MacLeod (incompetech.com), licensed under CC BY 4.0. Original track. Playback copy normalized, faded and compressed to MP3.
Interface Sounds · confirmation_001 by Kenney; Victory by Umplix. Sound effects: CC0. Effects converted to MP3, with volume adjusted; correct bell layered.
Vocabulary and example-sentence readings are AI-generated English audio.
Confetti animation: canvas-confetti, ISC license.
Spelling trial music: Adventures in Adventureland by Kevin MacLeod, original track, CC BY 4.0.