From Sonic Retro

Category: Graphics editor
Status: Active
System: Web Browser
Supported Games: Sonic 1, Sonic 2, Sonic 3 & Knuckles
Credits: snkenjoi
Thanks: FraGag, Flamewing, MainMemory, MarkeyJester, cwfluff and Xenowhirl

Flex is a web based tile / mapping / DPLC editor for Sonic 1, Sonic 2, Sonic 3 and Sonic & Knuckles made by snkenjoi.

It was created in an attempt to address some issues people had with SonMapEd, specifically with reading certain data formats and greatly improved image importing functions. It has various extra features, and more information on this can be found in the forum topic.