Sources

Dev interviews

• Lava Cut Content: Sugimori and Masuda on Gen 3's Development, translated long-form interview. The "all new Pokémon" plan, why older Pokémon were re-included, Hoenn-as-Kyushu rationale.
• Gamnesia: Game Freak Wanted to Capture Nature in Pokémon Ruby and Sapphire, Masuda quotes on Hoenn as childhood Kyushu.
• Pocket Gamer: Game Freak: We'll make the games we want to make, then choose the hardware!, the studio's design-first / hardware-second philosophy.
• Internet Archive: Junichi Masuda & Shigeru Ohmori interview (Omega Ruby / Alpha Sapphire era, 2014), the ORAS-remake interview that retrospectively discusses Hoenn's design.

Wikis & references

• Bulbapedia: Junichi Masuda, directorial credits, biography, design philosophy summary.
• Bulbapedia: Battle Frontier (Generation III), exhaustive coverage of the seven facilities, their rules, and the Frontier Brains.
• Bulbapedia: Battle Tower (Generation III), the R/S-only version that the Frontier replaced.
• Pokémon NJ Wiki: Emerald changes from Ruby & Sapphire, a near-complete diff between R/S and Emerald (story, gym leaders, sprites, Frontier).
• PKMN.NET: Battle Frontier Guide, community-curated facility-by-facility strategy guide.

Wikipedia

• Pokémon Ruby and Sapphire: release history, sales, reception.
• Pokémon Emerald: Emerald's specific changes and reception.

Reception & critical analysis

• Game Rant: Similarities and Differences Between Ruby, Sapphire, and Emerald, accessible summary of the three games' differences.
• Psypoke: The Battle Frontier, long-form fan guide to Emerald's post-game.

Visual reference

• Game UI Database: Pokémon Ruby, Sapphire and Emerald (id 1708), the source for every screenshot under docs/public/images/pokemon-rse/. Title screens, menus, battle UI, stat panels, contest moves, area map, trainer card. Provenance per-image in that folder's CREDITS.md.

Community math references

These two are the canonical reverse-engineered Pokémon math sources. If you're trying to understand how IVs/EVs/Natures actually work, this is where the formulas were originally documented:

• Smogon University: the de facto competitive Pokémon community since the early 2000s. Damage-formula breakdowns, set archives, generation-by-generation analysis.
• Bulbapedia: Stat formula, exact formulas for HP and the other five stats, with worked examples.