This is a romhack for Pokemon Emerald that randomizes your party's pokemon at the beginning of every battle; each pokemon in your party becomes a new pokmeon chosen randomly from every pokemon in the game. It preserves EVs, IVs, contest conditions, HP percentage, XP percentage, shiny/pokerus, and nickname across randomizations, and the moves of the new pokemon are the same as if they were found in the wild at that level. Pokemon will also be added to the pokedex if you get them through randomization. I made this romhack for SmallAnt to stream by request. You can watch him play it here.
Downloads can be found on the releases page of this repository.
The hack is distributed as a .bps file used to patch your Pokemon Emerald ROM. You must acquire a Pokemon Emerald ROM to use this romhack; the patch file only contains my changes. .bps patches can be used with a patching tool called Flips or directly inside some emulators. The ROM to patch is release #1986, which should be Pokemon Emerald U/E. The correct ROM should have the SHA1 checksum f3ae088181bf583e55daf962a92bb46f4f1d07b7 if you want to check that. After patching your ROM (either by creating a new file or in-emulator), the randomizer will just work!
This randomizer works by modifying the code that's called at the beginning of every battle. In the pokeemerald project the function that's modified is SetUpBattleVarsAndBirchZigzagoon in battle_controllers.c. All it does is call my custon function rndParty if the check for being the first battle fails. Note that all the code is marked as static methods -- this is on purpose to make compilation easier by avoiding introducing another file to link, since the setup can be a little precarious.