Most reward credit cards involve Byzantine point systems. Cryptocurrency firm Gemini is proposing a simple flat rate for its rewards — in Bitcoin. Founded by the Winklevoss Twins, Gemini is partnering with Mastercard to deliver up to 3% back in Bitcoin or one of the other 30+ cryptocurrencies they handle. More specifically, it offers up to 3% back on dining, 2% back on groceries, and 1% back on other purchases. The card will be rolled out this summer; interested parties can get on the waitlist now.