Hitbox

A hitbox is an invisible shape commonly used in video games for real-time collision detection. It is often a rectangle or circle (in 2D games) or cuboid, cylinder, or sphere (in 3D) that is attached to and follows a point on a visible object. They are used for collision detection.

Types

Collision hitboxes

Many hitboxes push Mario away, such as those of Bob-ombs and Chuckyas. These are necessary for Quick Release and are also the basis for the Bloated Bob-omb and Handsfree Teleported Bob-omb glitches, which work because the Bob-omb's size is large enough that its hitbox pushes Mario back, but it moves with him because he's holding it.

Clone hitboxes

Cloned objects that Mario can pick up normally act normal when set down, and have normal hitboxes. However, clones of objects never meant to be held have odd hitboxes. The majority of them can be interacted with only once by Mario, if at all. Platforms are intangible, and most enemies can injure Mario once and then become intangible. Coins can only be collected once, but don't disappear.

Overshadowing

Clone hitboxes overshadow the hitboxes of other clones of the same type. For example, Mario can release a fire clone and will immediately get burned by it. Then, he can stand in its (now dormant) hitbox to release another without getting burned. This serves many purposes in the A Button Challenge, including Bowser in the Sky and Tick Tock Clock.