Cuphead is now two years old and has sold five million copies across all platforms. To celebrate, Studio MDHR are planning "5 days of fun and giveaways" which begins with a sale of 20% off their game, no matter where you buy it from. Steam, Humble, GOG, it's on sale everywhere. Except in Tesla cars, I guess, where you can get the first zone for free as part of software version 10.0, and play it while you're parked using a USB controller.
(Image credit: Studio MDHR)