Sonic Next Genesis a hack of Sonic the Hedgehog inspired by a the 2006 game Sonic the Hedgehog but mostly contains custom content.

Credits:
RedHotSonic - Sonic 3K's Priority Manager in Sonic 2
MarkeyJester - 128 Variation of Disassembly, Background Deformation Code, ASM Guide
HiveBrain - Sonic 1 Disassembly
Mercury - ReadySonic
vladikcomper - Background Deformation Engine
Stealth - SonED2
MainMemory - SonLVL and related programs
Xenowhirl - SonMapED, Sonic 2 Disassembly
snkenjoi - Flex
Tornado - Water Guide, Sonic 3 Sound Driver in Sonic 1 Tutorial
DemonFox - Caterkiller Fix for 3K's Priority
MoDule - Sonic 3K's Priority Manager in Sonic 2
shobiz - Sonic 3K's Ring Manager in Sonic 2
Sonic master and hitaxas - Splash Screen Tutorials
Kram1024 - Sonic 3K's Sound Driver in Sonic 1
ValleyBell - SMPS Research
flamewing - SMPS2ASM
Dolphman - Genesis-style Sonic Advance badnik art
x\\\_justicehunter\\\_x - Silver sprites
Damien - Shadow Sprites
The creators of all the Sonic 1 and 2 Sonic Retro SCHG and SSRG tutorials
SSRG and everyone on it
People who contributed art to The Spriters Resource
My cat Nicole for sitting with me while I worked on this
And many other people I likely forgot to credit