Sonic Chaos (Master System prototype; 1993-06-30) - Sonic Retro

Sonic Chaos (Master System prototype; 1993-07-13)/Hidden content - Sonic Retro

Sonic Chaos (Master System prototype; 1993-06-30)/Comparisons - Sonic Retro

Sonic The Hedgeblog — From @HiddenPalaceOrg's May 17, 1993 prototype of

Game Gear - Sonic Chaos - Sonic (May 17, 1993 prototype) - The Spriters Resource

Sonic Chaos (Jun 30, 1993 prototype) - Hidden Palace

Sonic Chaos (Jun 30, 1993 prototype) - Hidden Palace

Sonic Chaos (Master System prototype; 1993-06-30)/Comparisons/Turquoise Hill Zone - Sonic Retro

Sonic Chaos (Master System prototype; 1993-06-30)/Comparisons/Special Stage - Sonic Retro

Sonic Chaos (Jun 30, 1993 prototype) - Hidden Palace

Proto:Sonic Chaos (Game Gear)/May 17, 1993 - The Cutting Room Floor

US7408108B2 - Multiple-paramenter instrument keyboard combining key-surface touch and key-displacement sensor arrays - Google Patents

Sonic Chaos Proto (June 30th, 1993) - Boss Theme BETA

Sonic Chaos Prototype (July 13, 1993) - Boss Theme BETA

US20150204559A1 - Adaptive pattern recognition based controller apparatus and method and human-interface therefore - Google Patents