The app just alerted me to this promo code for a one day sitewide sale, works on desktop + app :)
Extra 15% OFF off is valid sitewide only, until midnight 24 November 2017. Discount is not valid with gift card deals, or any deal where payment is not completed on the Groupon website (for example: ticketing deals that redirect to a third-party website for purchase). Exclusions apply: check deal page Fine Print before purchasing.
Enter code at checkout. Cannot be used with another discount promo. Discount will be applied to a single voucher in a transaction. Unlimited redemptions per customer (across separate transactions). Maximum discount of $40.