Sonic 1 Definitive (or Sonic 1: South Island Definitive) is an in-progress ROM Hack of Sonic the Hedgehog being worked on by RadiantNexus Team. It seeks to re-imagine the entirety of Sonic 1 under the lenses of what if Sonic Team revisited Sonic 1 in 1995, by re-adding scrapped content and expanding on the game in general.
Having started in 2019, it won the Judged 1st place trophy for Sonic Hacking Contest 2021.
Sonic 1 Definitive provides examples of:
- Adaptation Expansion: A game which originally had 6 zones (7 if you count Final Zone), is planned to have 13 zones, all of which are straight from Sonic 1's 16-bit release, its 8-bit release, or concept sketches.
- Alongside this, elements that were once only shown in the manual are already being built upon in the game itself, even in the SHC 2021 demo. The original intent for the final area of Green Hill Zone Act 2, filled with green crystals, for example, is meant to be Robotnik mining for the Chaos Emeralds.
- Art Evolution: The artstyle of the game is completely overhauled, resembling a merger between S1's geometric early 3D and some of Sonic 3's extra realism.
- Game Mod: The entire reimagining is built off the core of the original game.
- Green Hill Zone: Naturally, Green Hill Zone stays as the first zone.
- Idle Animation: As standard, Sonic has an idle animation based off his original one from Sonic 1. Plans exist, however, to extend it to include a reference to the Tokyo Toy Show's idle frame.
- Leitmotif: The theme of Green Hill Zone Act 2 is crammed full with them, with a reference to the version of Green Hill present in LEGO Dimensions, and a version of Green Hill done by the original composer
. - No Ending: Due to being unfinished, the planned ending is unimplemented. The current demo just ends in Sonic running to the right with "Thank You For Playing" showing on screen. The CGS 2023 demo concludes with a look at Spring Yard Zone's background while the credits roll.
- The Spiny: Yadorins/Spikeses are present in Bridge Zone, and in the future, Spring Yard Zone.
