Unloading the door in WWHD

(I think this is how it goes...)

There's a dungeon (Forsaken Fortress) you visit at the end of the prologue ("FF1") and again at the halfway point ("FF2"). FF2 is in the overworld, whereas FF1 is an almost-identical copy located in an isolated map, so they function like independent places. Completing both is required to not crash the game later on.

The intended prologue route is pirate ship → FF1, during which Link loses his sword; a (skippable) platform on FF1 changes the pirate ship from prologue to main state. Exiting the prologue ship is actually what removes the sword, which enables a wrong-warp from the overworld to FF1, because missing sword = being at FF1 as far as some enemies are concerned.

If you clear FF1 as normal, you're warped to Windfall, into a cutscene (meeting the boat). Clearing FF1, the game persists layer 0, which is the normal daytime layer (intended to prevent nighttime on first Windfall visit, I guess). Resetting the game/entering loading zones removes the persistence, which means entering FF2 switches to nighttime, adding 1 to the layer to make it layer 1, as it's always supposed to on FF2. But you can escape Windfall by "swimming" to FF2 with the right item. And then you're in FF2 on layer 0 (daytime!).

Getting that item before FF1 requires a hard trick (250 frame-perfect pauses?) so the old/beginner routes re-do FF1 after getting it (skipping the trigger the first time, then wrong-warping). Completing it the second time, the boat cutscene gets cancelled, leaving the game in layer 8, a *cutscene* layer. After "swimming", the post-FF1 persistence means you're in FF2 on layer 8.

Normally, there's a boss that requires some random item to defeat to open the door to end FF2. To skip that, there's a super-inconsistent *door clip*. But. In layers 0 and 8, the door at the end of FF2... doesn't load. Nor does anything else on the island for that matter. So you skip half the game *clap*.