Damage meter

The damage meter (also called the damage gauge, stamina meter, HP meter, HUD, player display, or health meter, among other names) is a UI element displayed during gameplay that presents basic information and status for each player at a glance. True to its name, the meter most prominently keeps track of a player's damage, though other statistics are generally shown here as well.

Layout
The damage meter displays the damage percentage a player has accumulated (shown down to tenths in Ultimate), as well as their score or number of stocks remaining where appropriate. These are superimposed over the character's series symbol. Starting with Brawl, the background of the meter also contains the character's portrait and a name bar; Ultimate would see a further redesign of these elements with an angled portrait and darkened name bar backing. The number of stock remaining is represented by the number of icons (nondescript pips in Brawl, the character's head in other games), while score is displayed with a simple integer value. A stock higher than five (six in the original game) is represented by one icon with a multiplier value next to it; having fifteen stocks, for instance, would show "× 15". In Brawl onward, the damage percentage itself can be disabled in More Rules, although all other elements will still be displayed. Scores in time battles can also be toggled on and off starting with Melee, although they are off by default; while a default feature in later games, Melee itself requires players to unlock this toggle by accumulating 5,000 KOs on their save file.

Generally, damage meters are fairly compact and overlaid atop the gameplay at the bottom of the screen, although Smash 4 also contains a vertical, full-screen variant that's instead shown on the system's secondary touchscreen; the 3DS version uses this variant almost exclusively (and additionally allows players to choose whether damage is displayed above or below the portrait), whereas the Wii U version merely has it as an optional feature. While normally opaque, on-screen damage meters from Brawl onward become translucent if a character goes behind them. The damage percentage itself changes color when more damage is accumulated. At low percentages, the value is white, but gradually turns maroon as it increases, reaching its darkest at around 300% (200% in Smash 4); starting with Brawl, the value will also shift through red first, and Smash 4 further adds a yellow hue before that. In addition, the Wii U version of Smash 4 displays the value with a metallic gradient. Starting in Brawl, the damage meter of a character who is KO'd appears to more or less "explode", and starting in Smash 4, the on-screen damage meter of whoever made the KO is briefly engulfed in flames.

In free-for-alls, the background of a player's damage meter is colored depending on their controller port: for human players, Player 1 is red, Player 2 is blue, Player 3 is yellow, and Player 4 is green, while CPUs are gray. In team battles, the coloring is instead based on players' teams, with CPUs using a paler tone than human players. As of Smash 4, more colors have been added for amiibo support and 8-Player Smash: Player 5 is orange, Player 6 is cyan, Player 7 is purple, Player 8 is slate, and amiibo FPs are rainbow-colored. Certain bosses in Smash 4 also have unique meter colors. As of Ultimate, Player 8's color has been changed to purple, while Player 7 is now pink, effectively replacing the slate color, and amiibo FPs have been changed to a yellow to blue gradiant. If 5 or more players are playing, the damage meters will be smaller than playing with 2-4 players.

Starting with Brawl, a player's current damage percentage will also occasionally display where their player marker usually is. This is generally only while at higher percentages in Brawl, but is more common in later games.

Additional info
The meter will sometimes show additional information during certain situations. This can be in the form of additional gauges and icons, or through alteration of existing elements. These include:


 * Opponents with certain status effects in single-player modes will have cosmetic effects applied to their damage meters in some way. Most prominently are metal characters: in Melee, this was denoted by darkened stock icons, and similarly in Brawl with a darkened character portrait. In SSB4, the portrait is shown in grayscale. The original game gave Metal Mario a series symbol unique in that it is shaded in order to convey a metallic look, though it is arguable if this could technically be considered an alteration, as Metal Mario in that game is treated as a completely separate character complete with his own series symbol, rather than simply with a Metal Box effect.
 * Alongside this, invisible and "dark" opponents in Melee have completely black stock icons, while false characters in Brawl's Subspace Emissary have a purple tint on their portraits.
 * Starting with Brawl, icons for any Dragoon or Daybreak parts a fighter has collected will appear next to their portrait.
 * In Ultimate, the player's current coin count will appear under the damage meter when playing on Golden Plains.
 * Starting with SSB4, certain characters will have additional info related to their abilities displayed on the damage meter:
 * Little Mac has a gauge above his damage meter that displays the charge for his KO Uppercut.
 * If Shulk currently has a Monado Art active, its symbol is displayed above his portrait (this is only shown on the on-screen meter in SSB4, and not on the touchscreen meter, meaning it is absent in for 3DS and does not show up on the Wii U gamepad).
 * In Ultimate, a gauge will also appear that shows how much time is left before the current Art expires.
 * In Ultimate, Cloud's Limit Gauge is constantly displayed above his portrait.
 * In Ultimate, the remaining durability of Robin's most recently-used move will be displayed above his portrait.
 * In Ultimate, Villager or Isabelle's currently-pocketed item will be shown above their portrait.
 * Inkling's Ink Tank is constantly displayed above her portrait.
 * Joker's Rebellion Gauge is constantly displayed above his portrait. If the match is not being played on Mementos or played on Mementos while a Persona 5 song or a remix is playing, it will be red. If on Mementos while a Persona 4 song is playing, it will be yellow. If on Mementos while a Persona 3 song is playing, it will be blue.
 * Hero's MP Gauge is constantly displayed above his portrait. Command Selection also displays a menu in front of the damage meter.
 * When Terry is above 100%, a flashing "Go" icon will appear above his portrait, indicating that he can use the command moves Power Geyser and Buster Wolf.
 * Steve's resources are shown above his damage meter, indicating how much dirt/sand/wool, wood, stone, iron, gold, and diamond he has in his inventory.
 * Kazuya's name will flash red when Rage Drive is available.
 * Sora's next Magic spell will appear above his damage meter.
 * Should Kirby copy any ability that displays this kind of additional info, he will gain the appropriate elements on his meter.
 * Also starting with SSB4, certain events will cause the portrait's eyes to flash. This happens when a character activates a Final Smash, fully charges certain special moves (such as Giant Punch or Charge Shot), or in Ultimate, perfect shields an attack. If a character receives an upgrade in the Find Mii stage, their portrait's eyes will glow constantly for the duration of the boost.
 * Ultimate introduces additional cosmetic effects that encompass the entire meter. When a character is at 120% or above, the damage meter will start smoking, doing so more violently at higher percentages. The meter will also continuously crackle with electricity while the character is in the standby state for a Final Smash.
 * In Ultimate, the character's name will be replaced by the player's name if one is selected.
 * In Ultimate, the new Final Smash Meter is displayed below the character's name when toggled on.

Stamina
In certain scenarios such as Stamina Mode or fights with bosses, a character's health is measured in HP rather than damage. In this case, the meter remains largely the same, though the value is affixed with an "HP" symbol rather than a percentage sign, counts down upon taking damage rather than up, and, in the Wii U version, shift through other colors, such as starting silver then turning bronze. These can appear alongside normal damage meters, such as the Master Hand fight where the boss's health is an HP value while the player retains the usual damage mechanic.

A different type of HP meter is used in the Subspace Emissary for all non-Smasher enemies, as well as in Brawl's Boss Battles mode. These meters are displayed as a horizontal red bar similar to a more traditional health bar rather than an exact numerical value, and appear above their owners for minor enemies and at the top of the screen for bosses. They are generally more difficult to strategize around, as one does not know exactly how much health an enemy has, especially since this kind of meter seems to be somewhat non-linear. Ultimate will go on to use the same kind of meter for all bosses in all modes, including Classic Mode.

Unique among all enemies is Master Core in Super Smash Bros. 4 - its meter at the bottom of the screen is obscured by a Swarm cloud in the 3DS version and disappears entirely in the Wii U version, intentionally making it impossible to know its maximum and current HP. In the 3DS version, once Master Core is defeated and reaches its final, vulnerable form, the Swarm obscuring the meter clears to reveal the boss's identity and a standard damage percentage starting at 0%, as it must be KO'd normally to finally end the match. The meter does not reappear in the Wii U version, but the final goal remains the same.

Trivia

 * In Melee, when a character reaches a higher-digit damage value, their damage meter displays a leading zero on the frame they get hit. For example, raising one's damage from 7% to 12% will have the meter display 07% for one frame before it changes to 12%.
 * In Melee, if a player is KO'd by a teammate, their damage meter returns to 0% using the "healing" animation instead of the "falling off" animation, before rising up from below the screen as usual.
 * In 64, Melee and Ultimate, the damage meter will no longer shake if an opponent is hit while at 999% damage, while in Brawl and Smash 4, it will.
 * However, in Ultimate if the meter reaches 999% and the opponent is hit while the damage shake animation from the previous hit is still playing, the shake animation will still occur, and will continue to occur for as long as the chain is maintained.
 * In Brawl, the black outline around the damage text is not part of the number textures like in the previous two games; it is instead drawn in real-time.
 * Early footage of arguably seemed to show the damage value also shifting through a greenish hue before turning yellow; if this was actually the case, it is no longer so in the final release.
 * When a character gets Screen KO'd in Brawl and SSB4, they will respawn before the "number breaking into pieces" animation even completes, resulting in the pieces disappearing abruptly. This can also happen with Share Stocking.
 * During online matches in for Wii U, the flame effect signifying a KO may appear over the wrong player's damage meter. This is a glitch caused by the game not accounting for damage meters being moved to show each player as player 1 on their own screen.
 * The damage meter in for Wii U has a subtle error. When the numbers on the damage meter shatter into pieces (character is KO'd), the "%" part of the number instantly disappears instead of falling off like the rest of the number. This problem does not occur when testing a Stage Builder stage or in early builds of the game. It does not happen in either.
 * For unknown reasons, the decimal separator in Ultimate’s damage meter will move up after the first time damage is taken, and will not go down even after losing a stock or healing to 0%.