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When the physics engine panics and flings your character across the map at absurd speed because two colliders disagreed.
Zips occur when the game's collision system tries to resolve an impossible position (like the player being inside a wall) by applying a massive velocity correction in a single frame. The result is the character being launched at extreme speed in an often unpredictable direction. Some zips are triggered by squeezing between two moving objects, standing on specific geometry seams, or getting crushed in just the right way. The distance and direction of a zip depends on the exact collision math, meaning they often require pixel-perfect setup positioning to produce consistent, useful results rather than random death launches.
Example
In The Legend of Zelda: Twilight Princess, the 'Back in Time' zip involves Link being crushed by a specific object, triggering a collision resolution that displaces him so violently it corrupts the game state. This single glitch enables the entire any% route by essentially breaking the game's concept of where you are.
Why it matters
Zips demonstrate what happens when physics engines encounter edge cases their designers never tested. They're often the most dramatic-looking glitches in speedruns: one frame you're standing normally, the next you've teleported across the entire map.
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