Steam launched a sale codenamed "0451"

Discounts affected 23 projects, including not very well-known indie games, and large projects, including Firewatch, Dishonored 2, Deus Ex and others.

0451 - this combo, which became a meme, and gained widespread acceptance, reaching many games. According to one of the versions, the code 0451 is a reference to the novel by Ray Bradberry called "Fahrenheit 451". Another variation says 0451 is the code in the office of Looking Glass Studios, the company that developed System Shock, a cyberpunk game.