Celeste (2018) is a very hard climbing game where jumps are measured in pixels. So the game is kind about one thing: for a tenth of a second after you run off a ledge, it still lets you jump. In the code the Celeste team released, a timer called jumpGraceTimer stays at 0.1 seconds while you stand and drains after you leave the edge; press jump while any is left and you jump. At full speed that's about one block of thin air.

Programmers call it coyote time. Maddy Thorson, Celeste's director, is clear that the team didn't invent it: "I don't think that we invented any of these techniques." Celeste stacks more like it: a jump pressed just before landing still counts, and holding jump gives the top of the arc half gravity. In Thorson's words, "everything is fudged a tiny bit in the player's favor," and "it wants you to succeed."

The runner, the ledge and the numbers in this film are our own simplified version, built in code from the constants in the released Player.cs. The strict run that falls is our own demonstration.

Which game's hidden rules should we cut open next?

Sources: Maddy Thorson, "Celeste & Forgiveness", maddymakesgames.com. Celeste's Player.cs, released by the developers on GitHub (NoelFB/Celeste, MIT license for the code).