Glitchy Ledge Grab

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GLG at SA Entrance

A glitchy ledge grab or GLG is a kind of ledge grab that goes higher than a normal ledge grab. While a regular ledge grab can only allow Mario to ascend up to 150 units, a glitchy ledge grab allows Mario to ascend up to 238 units. This can allow Mario to reach areas he could not normally, particularly in the context of challenges such as the A Button Challenge.

Details

If Mario is moving in the air with non-positive vertical speed, the game checks whether Mario can grab a ledge with two conditions. First, the game checks a 50 unit radius around Mario's position to see if there is a wall 30 units above Mario's position and no wall 150 units above Mario's position. Then, the game checks if there is a ledge Mario can grab on by looking at his x and z coordinates before being displaced by the wall and his y coordinate plus 160 units, looking for the highest floor below those coordinates, and checking whether that floor is at least 100 units above Mario. [1]. Additionally, when the game looks for a floor, it includes a 78 unit buffer giving the floor search an effective height of 238 units. A glitchy ledge grab occurs when those two conditions are satisfied in unusual ways, so Mario is able to grab a ledge he normally wouldn't be able to. A GLG can be triggered in a few ways:

  • The wall is slightly tilted, so Mario's lower point is within range of it but not his upper point, which triggers a ledge grab check when there is not supposed to be one (used in the A Button Challenge to enter The Secret Aquarium 0xA) [2]
  • Mario's lower point is near a wall, but it detects the wrong floor because of a difference in the orientation of the wall hitbox and the direction the game uses to find the x,z position the floor is searched in (used in the A Button Challenge to go to Bowser in the Sky 0xA) [3]
  • Mario's lower point touches a wall that ends as intended, but it detects the wrong floor because the floor search starts 238 units above Mario, which is high enough to find an unintended floor.
  • Mario's lower point is near a wall, and his upper point is aligned exactly with a gap in the wall due to float imprecision. [4]

References