Pedro Spot
Pedro spots are geometric configurations in which a floor is vertically aligned and within 160 units of a ceiling. They must also be at least 1-2 units apart, depending on their position relative to the origin. Pedro spots have the unique property that by landing in one while in an air action, Mario's Quarter Step is cancelled, yet he still technically "lands". This property leads to the fact that from a Pedro spot, Mario can both jump and Ground Pound, a property that is not shared by other spots in the game. Pedro spots have found two important applications in the A Button Challenge.
When Mario lands in a Pedro spot, he never physically enters it. Instead, he stays positioned in the air next to it. This allows a form of subframe grinding, allowing Mario to continue taking air steps while staying fixed in place. This can be used to build forward speed until Mario breaks out of the spot.
The other main application of Pedro spots is Remote Lava Boost (RLB). When Mario lands while in the lava boost action, the game checks whether he is above a lava floor, and if so, boosts him again. If Mario lands in a Pedro spot while in the lava boost action, the game will consider him to have landed, and so will check the floor beneath Mario. However, because Mario is next to the Pedro spot and not in it, this floor may be far below Mario. This causes the game to trigger another lava boost without Mario touching lava.
Pedro spots are very closely related to squish cancel spots.