Each round one auction card is revealed. Everyone bids in secret;
the highest bid wins. Treasures give you gems for your collection.
Loans give you cash now but cost you at scoring. Invests are free
money. The winner reveals one gem from their hand into the public
Value Display, which sets how much each color of gem is worth at
end-of-game (per the chosen chart). Missions auto-complete when
your collection covers them.