Enum Deck 

pub enum Deck<const CARDS: u8> {}

Origin marker for card-deck entropy. CARDS is the deck size; the entropy a full shuffle delivers is log₂(CARDS!) bits.

• Deck<32> — Skat. ~118 bits, too small for BIP39.
• Deck<40> — Spanish baraja, stripped. ~159 bits, 12-word only.
• Deck<48> — Pinochle / Spanish baraja (full). ~202 bits, 12-word only.
• Deck<52> — standard poker / playing cards. ~226 bits, 12-word only; never use for 24-word mnemonics.
• Deck<58> — smallest deck that clears 256 bits (~260). First size that supports 24-word mnemonics.
• Deck<78> — Tarot. ~380 bits, 12- or 24-word.
• Deck<108> — UNO (pre-2018). ~575 bits, 12- or 24-word.
• Deck<112> — UNO (2018+). ~599 bits, 12- or 24-word.

Greater the deck, fewer the draws, but the harder the UX.