Sonic Blast/Green Hill Zone

Act 1
The first act of Green Hill Zone is a simple run to the right. There aside from the enemies, there is one hazard - a spinning spiked log to between the two loops, just after the place where you can take the upper path.

When you reach the waterfall, you can either go through the water and jump on the platforms, or take the upper, faster route.

The large ring to the special stage is located in the pool under the waterfall. Jump in, and head all the way to the right, past the breakable blocks.

The exit is just after the third loop.

Act 2
This act in the Green Hill Zone will have back-and-forth travel to the exit in the bottom right.

Run to the right until you reach a red pipe that will take you down.

After exiting the one-way red pipe, Knuckles can climb the right-hand wall to reach an extra life.

Act 3
Knuckles can hit a red button in this area. After running to the right, jump at the last second before falling from the breakable bridge. When you are at the right height, glide to press it.

Head to the right to challenge Dr. Robotnik. He will approach from the right in a helicopter, and release a boomerang. It will fly in a circular fashion before returning.

His craft is vulnerable at the windshield. He can also damage you with the propellor, but only if you overshoot the windsheild.