First of all, a reminder of what ledgecanceling is.
In the void we can write tiles by changing our gfx set, like grasstiles and sandtiles. If we also have the correct ASLR, which is the randomisation of RAM initiated on booting the game, we can write a bikeledge in the void.
Interesting things about the bikeledge; the game doesn't actually disable your menu when on top of them, usually momentum does. And you should require momentum to enter the bikeledge under normal circumstances. But if you use the void you can write those tiles but they will update once you already stand on them. Therefore you won't have momentum!
So, we step onto this tile, the ledgetile moves the player left and we can now still open your sidemenu or use key items. This is known as ledgecanceling, even tho technically only the sidemenu stops the player from moving. This in itself can make loadlines move, causing custom tweaking areas, walk through walls and way more. But that's not what we're gonna be talking about right now.
What's important to know is that while opening the side menu, the game can still move you until the menu is actually on screen. This is a few frames, enough to move into another map id in the void. We call this Window Map Swapping.
Now this is where it gets interesting. The game assigns a Menu Id to you when opening a menu, and determines all functions based on that menu Id, not your current Map Id!
This means that if you open your sidemenu on the last frames of moving from an outdoor map into an indoor map, the menu will still allow you to fly, use bike and more importantly use Explorer Kit.
Explorer Kit, as some may know, writes your current Map Id and coordinates to [base]+1488 in RAM, which is also used by union room and allows us to wrongwarp to it. But since we can use Explorer Kit and any other outdoor function indoors, this means we can wrongwarp to the Map we moved into.
Next to that, Window Map Swapping also allows you to get NPC storage, which crashes the game after a few seconds, get a new error screen that saves the game but then puts you back into it without clearing RAM first, save inside maps that have mapscripts and the list goes on. I will make a video about all subglitches of ledgecanceling and Window Map Swapping soon!