Sonic Advance Revamped

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Sonic Requeset is just your generic Sonic fan game.

A Sonic fan game set in the SatAM universe.

A fanmade remake of both Sonic the Hedgehog Chaos and Sonic the Hedgehog Triple Trouble for Sega Game Gear, featuring new characters and habilities, new zones and levels, red star rings to unlock new stages, blue spheres special stages, Time Stones, a 16 bit music mode, a hub world, Ultra transformations, a pause menu, a debug mode and cheats, new color palettes and new player camera, gamepad support, 30 and 60 fps support, 4:3, widescreen and ultrawide.

Sonic the Hedgehog 3D is a free fan game about a famous SEGA mascot, Sonic, and it is made on Build Engine with additional EDuke 32 port. The game was inspired by two classic Sonic series: Mega Drive/Genesis and Sonic Adventure series.

Sonic Outbound is a Sonic fan-game set one year after Sonic Mania's bad ending where Robotnik had the Phantom Ruby and Chaos Emeralds in possession. After the final battle in the core of the Titanic Monarch, Robotnik was stuck in Little Planet and started collecting the Time Stones and preparing his greatest plan yet.

A 2D Sonic the Hedgehog fangame made with Clickteam Fusion

The world is a chaotic, terrifying place, rife with all manner of monsters, warlords and hostile architecture. Even for the mighty Pachacamac clan, just the act of survival is a day to day struggle, and everybody seems to know that they can't keep it up forever. In pursuit of a safe home, a lone shaman named Ichima happens apon the Special Stage - and with it, a means of realizing their dreams of safety and peace...

A flash-based Sonic fighting fangame based on Super Smash Bros. franchise. It has some characters from Sonic franchise and a campagin mode.
The game is an attempt at a mini-crossover with Sailor Moon, in which characters from that universe can be summoned by Sonic and his friends as helper characters with the use of Chaos Emeralds. It takes on an 8-bit Sega Master System style and is designed to look as authentic to the system as possible (I think).

Sonic World DX is a Heroes-style fangame with over 15 playable characters and 10 unique stages!