Bumper wall

Bumper walls are recurring gimmicks and loose variations of Springs. They made first appearance in Sonic the Hedgehog 2.

Description
These loose variations of regular Springs come as series of differently colored bouncy plates in row, which are placed on narrow routes and in gaps. These plates have shape of isosceles triangle with its left/right side pointing 70° downwards. Commonly, bumper walls are usually featured in amusement park and factory-themed Zones.

When the player enters the narrow route or gap, flat plates make the playable character move by being bounced from single plate to one placed in the opposite side of the route's ceiling or gap's wall. This way the player moves upwards, downwards or forward at high speed depending which direction plates are pointing. Certain games have ability to push the button down to make the playable character bounce faster.

Sonic the Hedgehog 2
Bumper walls were first featured in Metropolis Zone of Sonic the Hedgehog 2. These yellow plates are placed horizontally on rows at long pits. There are large amount of Rings set on these pits and Badnik is seen waiting at the top of the pit's edge to attack him.

If the player jumps to starting point of bumper wall and pushes, or  button down, the playable character bounces up on the corridor faster and progresses out of this section without problem.

Sonic the Hedgehog 3
In Sonic the Hedgehog 3, bumper walls are placed vertically on the ground and ceiling at long hall sections of Carnival Night Zone. These purple and yellow colored plates either bounce the player left or right depending the pathway.

In Gumball Machine-type of Bonus Stage there are bumper walls with yellow plates, which will disappear once touching one of them. They will help the player to reach large gumball machine above the corridor. Bumper walls with yellow plates are also featured in the Competition Mode's Chrome Gadget Zone, where they bounced the player down at high speed.

Sonic Pocket Adventure
Bumper walls with yellow plates made also appearance in Sonic the Hedgehog Pocket Adventure, where they are featured at Gigantic Angel Zone. They function identically like in Sonic the Hedgehog 2.

Sonic Advance series
Two Sonic Advance games features different types of bumper walls in many Zones. Casino Paradise Zone of Sonic Advance has vertically pointing ones placed on the ground and ceiling in lower tunnel sections of the Zone. These plates have flashing neon colors. Egg Rocket Zone features bumper walls set on long corridor sections with dark green plates being shaped of regular right triangles.

In Sonic Advance 2, Music Plant has rows of vertically pointing black and white piano keys set on long tunnel sections. Getting bounced by each key makes short piano jingle. Techno Base features triangle plates on corridor sections with flashing neon colors, which bounced the player upwards.

Sonic Heroes
In Sonic Heroes, there are upper corner sections on pinball tables of Casino Park with horizontally pointing bumper walls. These neon green and white colored plates send the player bounce upwards and usually guide the player out of pinball section.

Sonic the Hedgehog 4
Bumper walls made another appearance in Sonic the Hedgehog 4: Episode I and Episode Metal, where they are featured at Made Gear Zone. Usually set on corridor sections, these horizontally pointing brown plates bounce the player upwards like in previous games. However like in Sonic Advance 2, the shape of plate is now regular triangle.

Trivia

 * Certain Badniks like Slicers in Sonic the Hedgehog 2 are usually lurking at the top edge of bumper wall corridors. Normally the player would get hit by Badniks after reaching to the top and fall down. Pressing the jumping button down and choose the second plate above the first one will end up bouncing the player other direction and thus avoiding Badnik's attack.