Features
Almost all Pokemon from Gens 1 - 9 available (still need to add some Legendaries)
Vastly improved battle engine with modern mechanics and much smarter AI
Configurable Minimal Grinding Mode (MGM, described later)
Built in Difficulty Modes: Easy and Normal for now, would definitely be open to adding more options if there is interest (described later)
Built in Randomizer with configurable species and ability randomization (described later)
Built in Level Caps
Mega Evolution - New custom Megas added for several Pokemon, including Gen 4 starters, and several Gigantamax forms converted to Megas
Several Gen 4 characters added, including Dawn as an additional rival, all the Gym Leaders (only Roark is a required battle), and more!
DexNav
Toggleable following Pokemon
Gen 5 style party menu and Pokemon summary screen - Includes built in functionality to view EVs and IVs
Type icons displayed in battle
Move power calculator in battle
Sleep Clause
Heart Gold / Soul Silver style Pokedex
Form-changing Key Items for Rotom, Genies, Shaymin, and Hoopa
Form-changing NPC scripts for Silvally and Genesect (still requires their held items)
Cheat code system (available cheats listed in documentation)
Increased difficulty of trainer battles, with focus on Gym Leaders/Elite 4, Rivals, Team Aqua/Magma battles, route Mini Bosses, and optional Mini Bosses (over 100 of these battles in total!)
Several additional optional Boss Trainer battles (with hopefully good enough rewards to incentivize the player to actually want to do the battles!)
Some music from Gen 4
Balance updates for Pokemon to match Radical Red, which includes type-changes, stat updates, ability updates, learnset updates, etc. Differences from the RR balance changes are explicitly noted in the documentation, but the goal for this was to be able to match the data on https://dex.radicalred.net/ and to be able to reuse the damage calculator at https://calc.radicalred.net/.
Some fairly small story tweaks, mostly with the goal of lining up difficult battles
Heart Gold / Soul Silver style Pokedex
Post game Legendary events including access to Mystery Gift locations from vanilla Emerald
QoL Improvements
Not needing to teach HMs to use them, and they are forgettable if taught
Reusable TMs
Held Items are restored after battles
Bag sorting by Name and by Amount per pocket
Capability to register multiple Key Items
PokeVial with infinite uses to heal your party from anywhere
Access to the PC from anywhere
Time changer
Stat Editor (for EVs and IVs) given in Mauville
IV Perfecter NPC in Mauville
Hidden Power type changer NPC in Mauville
Toggleable Infinite Repel
Toggleable Auto Run
Hold R to speed through NPC dialogue
Option to rename a Pokemon in the party menu
Move Pokemon around in the party menu more easily with the Select button or the R button
Move-tutor moves converted to TMs so they can be taught anywhere, no more move tutors in game
Item care packages - Includes Infinite Candy, type-boosting Hold Items, type-resisting Berries, plus many more
Ability Capsules and Ability Patches to easily change between abilities for a Pokemon
In every Pokemon Center, a 2nd Nurse has been added who can: Change Pokemon's natures, Swap genders for Pokemon with gender-specific evolutions, Set Pokemon directly to the Level Cap
"Quick throw" option for Poké Balls in battle - Can scroll through options easily by holding the L button
Minimal Grinding Mode
It's the same as RR's. With MGM enabled, all Pokemon are guaranteed to have perfect IVs, and EVs are not obtainable for the player nor for NPC trainers. With MGM disabled, IVs are random, EVs are obtainable, options for instant EV and IV customization are still provided, and NPC trainers will still have perfect IVs and will be EV trained.
Difficulty Modes
"Normal: the intended difficulty of this game, and the one it was balanced for. Boss battles will be difficult, you cannot access the Bag during trainer battles, and the battle style is forced to Set.
Easy: this experience should still be harder than a vanilla Pokemon game, but should be considerably easier than Normal mode. All Boss Pokemon will be 2 levels lower than in Normal mode. Additionally, you can access the Bag during trainer battles, and you can change the battle style to Shift if desired, but it will still be Set by default.
Randomizer
Accessed in game.
The player can choose between normal species randomization (fully random), scaled species randomization (Pokemon randomize into Pokemon with similar base stats), and Legendary-aware species randomization (fully random, but ensures Legendaries get randomized into Legendaries), all of which applies to encounterable Pokemon as well as regular NPC trainers' Pokemon. Boss NPC trainers will never be randomized.
"Ability randomization is also configurable and is independent from species randomization.
List of abilities that are included/excluded from the randomizer is in the documentation.