SpelunkyFan wiki

Items freeze off screen

Verified against the spelunky.ai port v0.1.13 on .

Items freeze off screen is a quirk of Spelunky Classic in which a thrown item that leaves the view stops in mid- air until the view comes back.

A Rock thrown out of the view doesn't land somewhere out there: it stops in mid-air, a little past the view's edge, and waits. When the player comes back, it flies on from where it was, at the speed it had, as if it had just been thrown.

What happens

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The player throws a rock to the left from a running jump, and it flies out of the view. He walks away to the right, and comes back much later: the rock flies in from the left at the speed it left with, bounces off the cave's wall and lands [1].

Replays it in the game, where you can take over.Replays it in the game, to pause and scrub.
A thrown rock waits outside the view. The player throws a rock to the left from a running jump, and it flies out of the view. He walks away to the right, then comes back much later: the rock flies in from the left as if it had just been thrown, bounces off the cave's wall and lands, and he picks it up.

Why

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The whole of the items' step, the flying, the bouncing and the landing, is inside one test: that the item is within 16 pixels of the view, or is a rope:

if ((x > view_xview[0]-16 and x < view_xview[0] + view_wview[0]+16 and
    y > view_yview[0]-16 and y < view_yview[0] + view_hview[0]+16) or
    type == "Rope")
objects/oItem/step.gml:1-3, from spelunky.gmk, Spelunky Classic 1.1's source, © 2008, 2009 Derek Yu and Mossmouth, LLC (Spelunky User License v1.1b).

Outside it, the step does nothing, so the item keeps its position and its speed, and stays active, until the level deactivates it, 96 pixels or more past the view [2]. When the view comes back within 16 pixels of it, the step runs again with the speed it kept, and it flies on [3].

Reproducing it

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Throw a rock hard out of the view, then walk away and back. It happens whenever a thrown item leaves the view before it lands. The replay of the clip throws the rock at 14 pixels a step (frame 978). It leaves the view and stops in mid-air at (182, 226) on 990, still with that speed. The player walks right until the rock is deactivated (1063), then back: it's active again on 1126, still in mid-air, and flies on once it's near the view again (1154), bouncing off the wall and landing [4].

In the port

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The spelunky.ai port reproduces it exactly: it's in docs/quirks.md's list of the 1.1 source's bugs [3], and the oracle's fingerprint of the replay pins where the rock stops and when it flies on. No option turns it off.

FAQ

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Why does a rock I threw come flying back on screen in Spelunky Classic?

It never landed. A thrown item stops where it is once it's more than 16 pixels outside the view, still moving as far as the game knows, and goes on flying as soon as the view comes back near it, however long that takes.

Which items freeze outside the view?

The items that use the shared item step, the Rock for one. A rope doesn't: the step makes an exception for it.

Is a frozen item the same as a deactivated one?

Not quite. Further out, from 96 pixels past the view, the level deactivates things, items included, though it keeps more active to the right of and below the player. Short of that, an item is still active, but its step does nothing.

See also

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References

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  1. Clip quirks/rock-freezes-off-view
  2. objects/oLevel/step.gml:64-77
  3. Quirk 1 (docs/quirks.md)
  4. Replay fidelity/replays/item-seed-49-rock-off-view.txt

Source code

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