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 pillar.

• 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.

Sonic 2

• Metropolis Zone
  • Extends various rolling platforms.

Sonic 3 & Knuckles

• Angel Island Zone
  • Opens a passageway.
  • Destroys a bridge. (Act 2, when Knuckles presses it)

• Hydrocity Zone
  • Destroys another bridge (Act 1, when Knuckles presses it)

• Carnival Night Zone
  • Raises water and turns out the lights. (Act 2, when Knuckles presses it)
  • Turns the lights back on. (Act 2)
  • Reverses the direction of a gravity tube. (Act 2, when Knuckles presses it)

• Mushroom Hill Zone
  • Closes a door. (Act 1, when Knuckles presses it)
  • Opens that same door. (Act 1)

• Sky Sanctuary Zone
  • Extends a bridge (Act 1, when Knuckles presses it)