Flashcard system with "Abyss Vault" category.
- Spaced repetition algorithm featuring five mastery levels.
- Organize cards into "Data Streams" (decks) with selectable symbolic icons.
- Study sessions with card "decryption" (flip) and recall performance logging.
- Statistics tracking for total, due, and mastered card counts.
- Visual progress bars for each deck based on mastery percentages.
- Local data persistence for decks, cards, and review history.
- Dark-themed interface with neon-toned color palettes.