https://en.wikipedia.org/wiki/Konami_Code
The Konami Code (Japanese: コナミコマンド, Konami Komando, "Konami command"), also commonly referred to as the Contra Code and sometimes the 30 Lives Code, is a cheat code that appears in many Konami video games, as well as some non-Konami games.
⬆️⬆️⬇️⬇️⬅️➡️⬅️➡️🅱️🅰️
The code has also found a place in popular culture as a reference to the third generation of video game consoles, and is present as an Easter egg on a number of websites.