Special Stage (Sonic Chaos)

Sonic Chaos's incarnation of Special Stages are labryinth in design.

Overview
Much like the Special Stages in Sonic the Hedgehog (8-bit), these are maze/labryinth in design. As well being simple platforming levels, players enter the Special Stage upon collecting 100 Rings (mandatory or not) as Sonic only. Despite Sonic Chaos having Tails playable, only Sonic is able to gain entry.

Players have to simply navigate through the levels in order to reach the Chaos Emerald within the time limit. These Special Stages are notorious for their difficulty and strict time limit (except for the first one).

In this sense, while gaining entry is easy; getting to the Chaos Emaralds is rather challenging.