Hidden Island 9 shares Machine Labyrinth's design. Possessing an orange and green sky, the island is fully mechanical. It is dominated by metallic stream-powered machinery and factories, with various types of pipes, grids and large cylinder-shaped boilers everywhere. The only organic things on the island are orange-leafed bushes fenced in by wire grid fences. The buildings consist mostly of metallic archways and pillars on the inside and the winding roadways are made of grey beams webbed together.
Like most other Hidden Islands, Hidden Island 9 is a short stage which can be finished in less than a minute. The gameplay here relies heavily on the Hang Glider which is used for the majority of the stage; without it, the stage cannot be completed. Lesser gimmicks include Dash Rings and Rainbow Rings. Shisaku-gata Jets serve as midair hazards since touching them while gliding, but without boosting, will not bode well.
To begin with, the player has to ride a Hang Glider over an extended pit filled with Spikes. The player will then arrive on solid ground where another Hang Glider must be used to cross a bottomless pit, with the Treasure Chest waiting on the other side.