If you've been waiting for an opportunity to grow your Xbox One backward compatibility collection, now's the time to act as Microsoft has slashed prices on more than half of its library.

The Xbox One Backward Compatibility Super Sale, which runs through May 22, features sizable discounts on many Xbox 360 games that are playable on the newer Xbox One.

Highlights include Left 4 Dead and Left 4 Dead 2 at 75 percent off, several Call of Duty titles for half price, BioShock, BioShock 2 and BioShock Infinite for between 50 and 65 percent off, four Assassin's Creed games at 67 to 75 percent off, Grand Theft Auto: IV and Grand Theft Auto: The Ballad of Gay Tony at half price and several Gears of War titles for 75 percent off.

There are also a handful of add-on packs on sale for games like Destiny: The Taken King, Call of Duty: Black Ops II, Borderlands 2 and Red Dead Redemption, among others.

While on the subject, Microsoft has also put several Xbox One games like Final Fantasy XV and Mirror's Edge Catalyst up for sale with discounts ranging from 10 percent on up to 85 percent.

Full details on both sales, which are only valid for Xbox Live Gold members, can be found over on Major Nelson's blog.