Movement steps
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Typically, Mario's position is updated incrementally using his velocity. These increments are called steps, and they behave differently when Mario is on the ground, in the air, in water, hanging, and climbing a pole. When on the ground or in the air, these steps typically occur four times per frame, and are commonly referred to as quarter steps or sometimes quarter frames.
Steps are also responsible for detecting collision with surfaces, updating Mario's referenced surfaces, and updating Mario's water level. However, quarter steps don't detect warps.
Air Step
When an action performs an air step, the first thing Mario does is update his horizontal velocity/sideways position via straining.
After that is updated, the movement is split into "quarter-steps" that breakdown Mario's movement and determine what his outcome of each step is. The checks for the quarter-steps are as follows:
- The position a quarter of Mario's velocity ahead of Mario is checked for cancels/outcomes. Anything in bold is an exit out of the rest of the checks.
- If the position is above OOB but below Mario's current floor height, Mario's height is changed to the floor height and he lands.
- If the position is above OOB but not below Mario's current floor height, Mario's height is set to the new height and he hits a wall.
- If the action has the "riding shell" flag and the water level at the position is above the position's floor (up to 78 units above the position):
- The floor height from here on is the water height.
- The floor from this point on is a "fake" floor on the surface of the water.
- The floor's origin offset is set to the water height.
- If the position's height is 78 units or less below a floor and there is not a ceiling 160 units or less above it (because of how variable types an overflow jump may occur here):
- Mario's position horizontally is updated to the new position.
- Mario's height is set to that of the floor's height.
- Mario's floor and floor height are updated.
- Mario lands.
- If the position's height is 78 units or less below a floor and there is a ceiling 160 units or less above it (because of how variable types an overflow jump may occur here):
- Mario's height is set to that of the floor's height.
- Mario lands. (Because Mario's floor is not updated, this is where a pedro spot may occur)
- If the position's height is 160 units under, at, or above a ceiling and his vertical velocity is positive or zero:
- Mario's vertical velocity is set to zero.
- If the ceiling above Mario is hangable and the air step has the "check hang" flag, Mario hangs. (Since this did not use the new position's ceiling/location, this is potentially a hangable-ceiling upwarp.)
- Otherwise, nothing happens.
- If the position's height is 160 units under, at, or above a ceiling and his vertical velocity is negative:
- If the position's height is at or below Mario's floor height, Mario's height is set to the floor height, and he lands.
- Otherwise, Mario's height is set to the new height and he hits a wall.
- If there is a wall 30 units above the position but not 150 units above the position and the air step has the "check ledge grab" flag:
- If Mario's velocity is positive, Mario is pushed by the wall opposite the velocity direction, and there is a floor 60 units behind the wall within 238 units upward, Mario ledge grabs. (Potentially a GLG)
- Otherwise Mario's position is set to the new position, his floor and floor height are updated, and nothing happens.
- Mario's position is set to the new position and his floor and floor height are updated.
- If Mario is colliding with a wall 150 or 30 units up and the upper or only wall is lava, he lava wall boosts.
- If Mario is colliding with a wall 150 or 30 units up and Mario is facing perpendicular to 0x6000 units away, he hits a wall.
- If no other exit has occurred, nothing happens.
- This repeats until Mario encounters something besides nothing happens, up to four times including the initial time.
From here, the outcome chooses the next action and some other things are applied.