Button

In Sonic 3 and Knuckles and other games, and frequently exploited by Knuckles, buttons are pretty bog-standard items placed liberally around levels which alter something in the level when pushed.

Sonic 1

• Marble Zone
  • Raises a spiky metal stomper.
  • Moves a large green block.
• Spring Yard Zone
  • Opens doors.
  • Raises a platform.
• Labyrinth Zone
  • Opens doors.
  • Makes a hidden platform appear (act 1).
  • Changes the layout of the level (act 3).
• Labyrinth Zone (SMS/GG Version)
  • Changes a ring monitor into an extra life.
• Scrap Brain Zone
  • Changes the direction of a revolving wheel that grabs Sonic.
  • Causes the floor to collapse (act 2, when Dr. Eggman presses it).
  • Makes a large platform move down a slope (act 3).

Sonic 2 Beta

• Oil Ocean Zone
  • Releases a rolling ball