Shield

A shield (referred to as barrier in Japan) is a power-up that protects the player from harm. When the player runs into an enemy or trap, they fall backwards and the shield is lost. Shields offer limited protection in the same way as rings do, although shields can't be re-collected after they are lost.

Shields can be obtained though breaking monitors, or the gumball machine bonus stage in Sonic 3.

Types of shield

Sonic the Hedgehog, Sonic the Hedgehog 2 and Sonic Pocket Adventure

• The original shield is a simple blue sphere, with no additional advantages.

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  Sonic 1 (Mega Drive) shield monitor.

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  Sonic 1 (Mega Drive) shield.

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  Sonic 2 (Mega Drive) shield monitor.

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  Sonic 2 (Mega Drive) shield.

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  Sonic 1 (Master System) shield monitor.

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  Sonic 1 (Master System) shield.

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  Sonic Pocket Adventure shield monitor.

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  Sonic Pocket Adventure shield.

Interestingly enough, there are no shields at all in the 8-bit version of Sonic 2 and subsequent games (Sonic Chaos and Sonic Triple Trouble).

Sonic 3 & Knuckles

These shields protect against most projectile attacks. Sonic is able to perform special attacks by pressing jump twice, whereas Tails and Knuckles cannot. If the player collects a shield while under the effects of a super transformation, the shield graphic will not appear although its secondary effects will still apply (i.e. ring magnetism with the lightning shield).

• Insta-Shield: When Sonic does not have a shield, jumping twice gives you a split-second shield. This is particularly useful in certain boss fights, and against certain Badniks like Orbinaut.
• Water shield (or aqua barrier): this shield protects the player from drowning, and as such is particularly useful in Hydrocity Zone and other Sonic 3 levels which contain water sections (as opposed to Sonic & Knuckles levels, in which there isn't a single drop of water). Pressing jump twice lets Sonic perform a bounce attack, rapidly smashing down on the floor and then rebounding at height. The water shield also appeared in Sonic R, but with significant differences; it lacked the bounce technique, and allowed the character to walk on water rather than survive under it. The shield would also disappear once you touched back on dry land afterwards.
• Fire shield (or flame barrier): protects the player from flames. Pressing jump twice turns Sonic into a fireball which briefly zooms forward. Falling into water, however, will destroy it (although not if the player is in Super or Hyper mode). This shield also appears in Sonic 3D: Flickies' Island, but minus the fireball ability.
• Lightning shield (or thunder barrier): protects the player from electric damage and attracts nearby rings. Pressing jump twice lets Sonic perform a double-jump. As with the fire shield, water destroys this barrier (if the player isn't in a Super or Hyper form). The shield also appears in Sonic Adventure 2, Sonic Advances 1, 2 & 3, Sonic R, and Sonic Rush.

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  Sonic stands on a lightning shield monitor, with fire and water shields to his left and right.

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  Insta-Shield

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  Water shield.

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  Lightning shield.

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  Fire shield.

Sonic 3D: Flickies' Island

• The standard blue shield, which, contrary to its usual "everything-breaks-it" properties in all previous games, renders Sonic impervious to electric damage in this game, specifically the electrified floors in Gene Gadget Zone.
• The fire shield, which protects the player against fire and lava (especially useful in Volcano Valley Zone).
• The gold shield, which lets the player perform homing attacks on nearby enemies.

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  Shield monitor.

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  Standard blue shield.

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  Fire shield; walking on lava.

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  Gold shield; homing attack.

Sonic Adventure and beyond

• A green version of the standard blue shield.
• The magnet shield, a blue shiny shield which is the same as above except that it also attracts rings.
• A Fire Shield is present in Shadow the Hedgehog, which causes minor damage against the enemy that pierces it.