Mario Bros.

Mario Bros. (, Mario Bros.) is a stage that appears in Super Smash Bros. Brawl and Super Smash Bros. Ultimate, and is based on the arcade game of the same name. The versus mode level in ' (and its SNES/Wii counterpart ') and in  for the Nintendo Entertainment System (NES) and Wii, respectively, were also designed after this game.

Due to the fact that this stage has narrow KO zones and no lower blast zone, it is difficult to score a normal KO. Masahiro Sakurai himself said, "Speaking frankly, this stage throws all the basic rules of Smash out the window!" The best way to KO someone is to hit a Shellcreeper or a Sidestepper from below (through the floor) or attack one, pick it up, and throw it at someone before the player can get a KO. In Ultimate, it is one of the only two stages in the game (with the other being Balloon Fight) that allow players to walk off one side of the screen and warp around to the other side instead of self-destructing if there is no knockback or hitstun inflicted on a player.

is fought here when being unlocked in Brawl, even if this stage hasn't been unlocked beforehand. In Ultimate, 's unlock battle in World of Light is also fought here.

Stage Mechanics
This stage features a POW Block at the center of the bottom floor. Jumping into it from below or attacking it will result in it knocking every Shellcreeper, Sidestepper and character on the ground upwards. Unlike every other instance of this item appearing, characters do not take damage from this, and cannot be KO'd by the knockback, as the knockback is set at a very low height, meaning the only point of using a POW Block to flip a character would be to disrupt them. The POW Block takes three hits to destroy and respawns exactly thirty seconds after being destroyed.

Shellcreepers and Sidesteppers are the main hazards on this stage. They spawn from the top pipes in ten second intervals, with the first one spawning exactly ten seconds after the match has started. There can only be four of five hazards on the screen at a time. Once this limit has been reached and a hazard is thrown off of the screen, another one will spawn to take its place almost immediately within five seconds.

A Shellcreeper/Sidestepper can be flipped by either attacking them, jumping into the ground they are standing on from below, or hitting the POW Block. A Shellcreeper/Sidestepper will change color if it is flipped over and allowed to get back up by itself after ten seconds of being knocked down. This ten second time period is not reset by picking up the flipped hazard. A player can pick up a flipped Shellcreeper/Sidestepper as an item. It will always deal 16% damage for a normal throw, and 18% for a smash throw, regardless of color. They have the same traction and knockback as the stray ones, however. Thrown Shellcreepers/Sidesteppers will deal knockback at a semi-spike angle, making them ideal for KOing players between the various platforms.

If a Shellcreeper/Sidestepper runs into another Shellcreeper/Sidestepper (flipped or unflipped) or a player, it will change direction. The bottom pipes warp the enemies back to the adjacent top pipes. This effectively creates a "safe-zone" where players can constantly avoid the Shellcreepers, at the cost of being considerably closer to the blast lines. In-between the edge of the stage and the side blast lines, there is a "warp zone". Any Shellcreeper/Sidestepper that goes through this zone (except when thrown) will warp to the exact opposite warp zone and continue moving. This "warp zone" does not apply to players in Brawl but does in Ultimate if they get within 25 units of the blast zone (off-screen enough to hide the fighter in most cases).

Shellcreepers take one hit to flip over. Green Shellcreepers deal 11% damage, walk at a slow speed, deal (relatively) low knockback, and have high traction. Purple Shellcreepers deal 13% damage, walk at a medium speed, deal medium knockback, and have average traction. Red Shellcreepers deal 15% damage, walk at a fast speed, deal high knockback, and have low traction.

Sidesteppers take two hits to flip over; a Sidestepper who has been hit once will have an angry expression on its face. Red Sidesteppers deal 13% damage, walk at a medium speed, deal medium knockback, and have medium traction. Blue Sidesteppers deal 15% damage, walk at a fast speed, deal high knockback, and have low traction. Pink Sidesteppers deal 17% damage, walk at a very fast speed, deal very high knockback, and have very low traction. Sidesteppers use the slash effect. Both enemies have a high chance of tripping players.

The final hazard is the Flame. Flames always appear in one of eight places (just above each of the platforms and the ground on the left side, and ditto for the right side), deal 20% damage on contact, and have knockback that scales considerably with the player's damage percentage, becoming very strong at high percents. There can only ever be one Flame onscreen at a time, and they cannot be destroyed, stopped, reflected, or absorbed. They materialize and dematerialize in about 1.5 seconds and are unable to damage players while appearing/disappearing. After spawning, they travel in a wave motion horizontally to the opposite spawn point (about equal vertically to where the wheel is on the pipes), and then disappear. Flames appear to have no set timer for appearing and do not interact with the POW Block or the Shellcreepers/Sidesteppers.

Shellcreepers, Sidesteppers, and the Flame are all completely two-dimensional.

Ω form and Battlefield form
In Super Smash Bros. Ultimate, the main platform of the Ω form and Battlefield form is made of the bricks on the bottom of the regular form and is the same size and shape as and, respectively. Shellcreepers, Sidesteppers, fireballs, and POW Block are absent (save for the POW Block in the background). In the background is the layout of the regular form, darkened. The three soft platforms of the Battlefield form are based on the blue platforms of the regular form.

Origin
This stage is based on the design of the first two "Phases" of the arcade game  In Mario Bros., there are turtle enemies called "Shellcreepers" and crab enemies called "Sidesteppers". Shellcreepers and Sidesteppers come out of the top pipes and return through the bottom pipes. To defeat the enemies, the player has to knock them over from underneath the platforms, then kick them from the side. The player can also be knocked over if another player hits them from below, but all they do is jump a bit. In a pinch, the POW Block can be used to knock over every enemy on the screen. If the player leaves the enemies alone long enough, they get back up, change color, and move faster. All of these elements have been retained in the Mario Bros. stage.

Additionally, some elements have been modified for the stage. When an enemy is knocked out in Smash, the player can pick it up and throw it at other players as a projectile. In Mario Bros., red and green s can appear and travel across the stage. The red fireballs bounce off the ground as they go by, while the green ones don't succumb to gravity. This stage has only the green fireball, which still follows the same physics as the original game. Also in Mario Bros., both the player and enemies can the screen; exiting through one side results in reappearing on the other. In Brawl, this only applies to enemies, and players are still bound by blast lines. In Ultimate, the mechanic is more similar to Balloon Fight; players can wraparound the screen, but during knockback, the blast lines take effect.

Tournament legality
This stage is banned in all tournaments, due to the Shellcreepers, Sidesteppers, and the Flame drastically altering gameplay, focusing more on throwing the projectiles rather than using other attacks, and all three are overly powerful stage hazards. Because of the Shellcreepers and Sidesteppers, characters with reflectors have a huge advantage over characters that lack them. The stage also has a large size, walk off stage edges allowing for chain throws off the sides, and platforms creating caves of life allowing unusually high damage percentages.

Update history
 3.1.0
 * Mario Bros.'s on-screen appearances and revival platforms locations have been changed.

Trivia

 * This stage is one of only two stages in Brawl to be based on an arcade game, the other being 75m.
 * This stage is listed separately from the other Mario stages on the stage select menu, as is 75m from the stages.
 * Even though this stage is based on Phase 1 of Mario Bros., Sidesteppers do not appear as enemies until later phases in the game; only Shellcreepers originally appeared.
 * Two enemies originating from Mario Bros., the and the Freezie, do not appear on this stage; however, the Freezie appears as an item.
 * Even though this stage belongs to the universe, it serves as 's home stage in  and All-Star Mode since he is the only character in Brawl without a proper home stage, and a medley of tracks from the two NES/Famicom games that used R.O.B. (Gyromite and Stack-Up, though only the former is mentioned in the track's title) is available in this stage.  When this stage is not unlocked, Delfino Plaza is R.O.B.'s home stage.
 * In Brawl, all the music tracks on the stage are derived from at least one NES/Famicom game.
 * On most stages, the camera will zoom in and out during gameplay depending on how close or far the characters are from each other. Mario Bros., Flat Zone 2, Flat Zone X, Pac-Land, and Balloon Fight are exceptions to this rule; the camera stays in a fixed position to give a view of the entire stage.
 * There is a glitch that will turn Shellcreepers and Sidesteppers invisible while flipping them until they flip themselves back over. It is unknown how this glitch is triggered.
 * In Ultimate, on all forms of this stage, characters will make the same running and skidding noises as the Mario Bros. did in the original 1983 arcade game when moving or turning, though the sounds are from the 1983 NES version.
 * in Ultimate's Training Mode, the Shellcreepers and Sidesteppers do not freeze when the settings appear, unlike most other stage hazards. This allows them to walk past the bottom warp pipes without going into them.
 * Characters that follow fighters (the partner Ice Climber, 's Pikmin, 's Luma) can get confused on how to follow when the fighter wraps around the screen, either running faster to catch up and overshooting or running towards the opposite side. This scenario happens more often if the fighter has their speed increased (such as wearing a Bunny Hood or using certain spirits).
 * In Ultimate, the following Assist Trophies can only appear on the Battlefield and Omega forms of this stage: Arcade Bunny, Devil, Kapp'n, Rathalos, Squid Sisters, Thwomp, and Tiki. The Moon, Nikki cannot be summoned on this stage at all, likely due to the dark background. Additionally, the Poké Ball Pokémon, Abra and Lunala cannot only be summoned on the stage's Battlefield and Omega forms.