Bumpers are items that deflect the player back in the direction from which they were hit. They have appeared, in one form or another, in all of the Sonic the Hedgehog games. Their first appearance was, unsurprisingly, in Sonic 1's Spring Yard Zone. Although their visual style has changed through the games' timeline, their basic function remains the same: to serve as an obstacle in a pinball/casino-themed level.
It should be noted that bumpers are closely related to springs, in that while springs only catapult the player in one direction, bumpers bounce the player off in the same direction that they encountered the obstacle.
When hit, bumpers (in the 16-bit games) generally give the player a point bonus unless the player hits one too many times.
Found in Spring Yard Zone (and in the Special Stage), the Sonic 1 bumper is a blue circle semi-covered by a yellow five-point star, with a thin red outer ring. When Sonic hits this obstacle, the bumper expands slightly and propels him backwards. These are commonly found in the more open areas of the zone, where Sonic is free to bounce around pinball-style.
Found in Carnival Night Zone and the Special Stage, this level's bumper is a simple white orb with a red four-point star in the centre. These appear either alone or in groups, and are capable of movement in any direction. Some groups may rotate in a circle-like fashion, others form lines and spin parallel to a certain point.
A second kind of bumper can be found in the Slot Machine Bonus Stage.
The bumpers appearing in this game can be found in Collision Chaos Zone.
Spring Stadium had circular bumpers that have red/yellow alternating rings. The zone also has triangle bumpers on the corners of slanted areas in the zone.
Bumper Balls appear in the Special Stage.
Bumpers appear in Radical City's pinball table section of the course.