Help with Sonic 1 (Game Gear/DX)

Hokay, I finished the game for the first time yesterday, but with only four emeralds. I've scoured Scrap Brain Zone and have come up with nothing yet. The one-way teleports aren't helping, either. Can someone point out where that fifth emerald is? Thanks!

EDIT: Just to clarify, this is for the Sonic the Hedgehog 1 mini-game included with SADXPC. As far as I am aware of, it is identical to the Sega Game Gear version, so that may help too.

Ahem. Gamefaqs. Kthnx.

ORLY? OK. SOWWY. KTHNXBYE.

Sorry, couldn't resist. Thanks, though. I didn't realize GameFaqs had GameGear walkthroughs there (I haven't used it that much).

They have have walkthroughs for pretty much every game ever.

Oh, and it's 'sry', not 'sowwy'. Take note of this for future reference. ^_~