Sonic The Hedgehog Challenge Mode is a hack for a Sega Master System version of Sonic The Hedgehog. It changes level design and makes it harder, but it is not kaizo. Nice challenge for players who find the original game too easy.

There are no rings in the levels, but don't worry, you can find One-Up Monitors on every Act of the game, except Labyrinth Zone Act 1. At some stages you can even find Shield Monitors!

But I would recommend to be familiar with the original game before playing the Challenge Mode.

and yeah labyrinth is so much harder now