Meta-map script activation: Difference between revisions

'''Meta-map script activation''' refers to a set of [[glitch]]es in {{RBY}}. These glitches will modify the "meta-map script" (also known as GameProgressFlags in the Pokémon disassembly projects<ref>[https://github.com/pret/pokered/blob/master/ram/wram.asm Pokémon Red disassembly project WRAM]</ref><ref>[https://github.com/pret/pokeyellow/blob/master/ram/wram.asm Pokémon Yellow disassembly project WRAM]</ref>) associated with a certain map, which is a special map script used to execute code on particular maps (one byte for each map). An example of a meta-map script is one that sets the event in Pallet Town where Professor Oak stops the player from walking into the grass. It is disabled later thanks to the game changing the ID of the meta-map script later.

For example, item 100's quantity controls the map script for Route 8 (address D601 in Red/Blue, D600 in Yellow). Though a quantity of 1 for this item will set up a CD2D/Special-stat encounter (as if activating the Trainer escape glitch), out of bounds values are glitch scripts associated with this glitch. As in the usual Trainer escape glitch, bit 0 of $CD60 and $D730 must not be set for the CD2D/Special-stat encounter to appear. If the encounter doesn't occur even after preparing the Special stat/or CD2D, the player still has to reset them by changing boxes and resetting the game, and pushing a Strength boulder/having another Trainer walk up to the player [[Trainer escape glitch#Special stat encounter|etc.]]

This method is ideal for altering a meta-map script at ease, especially if it corresponds to an item quantity. The player may also be able to manipulate all 256 meta-map scripts for the map (but if the script corresponds with an item, manipulating a Cancel (0xFF) for script 255 might be harder). Furthermore, as there are only 256 item/quantity pairs in the expanded PC and the addresses after item 128 quantity are a mirror of items 1-128 again, it is usually only possible to corrupt up to D63A (W_MANSION1CURSCRIPT) thisin way.Red/Blue Theor first meta-script address RB:W_OAKSLABCURSCRIPTD639 (D5F0)both isW_CINNABARISLANDCURSCRIPT PCand item 91's quantity. The last accessible one (W_MANSION1CURSCRIPT) (D63A)in isYellow PCthis item 128's quantityway.