The 1P Game (also known as 1 Player Game, 1P Game Mode, or sometimes Classic Mode) is the only single-player campaign mode available to play in Super Smash Bros. In the mode, players progress through a series of eleven stages, culminating in a final battle with the game's boss, Master Hand. In addition, there are three optional bonus stages–one after every third match–where the player has one stock to complete the stage before time runs out. Clearing each stage, including the bonus stages, gives the player bonus points that contribute to a total score. The mode has a static nature in which the player faces the same characters on the same stages in a fixed order during each playthrough. Players may choose their character, the difficulty, and number of lives before the playthrough.
The 1P Game did not return proper in Super Smash Bros. Melee. In Melee, the aspect of fighting a series of opponents en route to Master Hand (and depending on the difficulty, Crazy Hand) was instead included in the redone Classic Mode. However, this mode in Melee featured randomized opponents and a more streamlined structure, alongside other improvements. Additionally, some fights from the 1P Game reappeared as opponent characters in the new 1 player mode Adventure in Melee (including the Yoshi Team, Giant Donkey Kong, the Kirby Team, and Metal Mario). In this regard, the Adventure mode can be seen as an enhanced remake of the 1P Game from Smash 64. In Super Smash Bros. Ultimate, Jigglypuff's Classic Mode route might be a reference to this mode (since its Classic Mode consists of only characters and stages from the original game; with its final boss as Giant DK).
Each stage, excluding bonus stages, has 5 minutes for the player to KO their opponent(s). However, the player is able to disable this time limit but doing so prevents the player from receiving time bonuses.
Stage 1: Link
Stage 2: Yoshi Team
The second stage takes place on Yoshi's Island and pits the player against the Yoshi Team, made out of 18 lightweight Yoshis. The Yoshis rarely attack and as they are lightweights, they are exceptionally weak and can be knocked out by almost any attack; sometimes they may even fall from the stage without any conflict from the player. Defeating the Yoshis in the order that they appear gives the player the Yoshi Rainbow bonus, worth 50,000 points.
This stage takes place on a version of Yoshi's Island without the clouds off to the side of the stage; while normally inaccessible, it is possible to access the stage via hacking.
Stage 3: Fox
Bonus Stage 1: Break the Targets
The first bonus stage is Break the Targets. It challenges the player to seek and smash ten targets placed throughout the stage within a 2-minute time limit.
Stage 4: Mario Bros.
The fourth stage takes place at Peach's Castle and pits the player against the Mario Bros., consisting of Mario and Luigi. In this stage, the player is accompanied by one, randomized ally. Curiously, Luigi will still appear even if the player has not unlocked him. Knocking out one Mario brother before hitting the other will earn the player the Bros. Calamity bonus, worth 25,000 points. Defeating both Mario Bros. without the teammate being KO'd nets the 8,000-point Good Friend bonus, while defeating them without the teammate being damaged at all earns the 25,000-point True Friend bonus.
Stage 5: Pikachu
Stage 6: Giant Donkey Kong
The sixth stage takes place in Congo Jungle and pits the player against Giant Donkey Kong. In this stage, the player is accompanied by two randomly selected allies. Defeating Giant Donkey Kong without either teammate being KO'd nets the 10,000-point DK Defender bonus, while defeating him without either teammate being damaged at all earns the 50,000-point DK Perfect bonus.
Bonus Stage 2: Board the Platforms
The second bonus stage is Board the Platforms. It challenges the player to seek and step on the surfaces of the ten platforms placed throughout the stage within a 2-minute time limit.
Stage 7: Kirby Team
The seventh stage takes place in Dream Land and pits the player against the Kirby Team, of 8 lightweight Kirbys. Each of the eight Kirbys sport a unique hat (with the exception of the final one, which will be either normal Kirby, or one of the four unlockable characters after they've been unlocked) corresponding to each of the eight starter characters in the game. There are always two Kirbys at a time for the player to face. Except for the average and unlockable character Kirbys, they all appear in the selection screen order of the respective character whose power they copied. Keeping this in mind, if the player manages to defeat them in the right order (Mario, DK, Link, Samus, Yoshi, Fox, Pikachu, regular/random unlockable), they will be awarded the 25,000-point bonus Kirby Ranks.
Stage 8: Samus
Stage 9: Metal Mario
Bonus Stage 3: Race to the Finish
The third and final bonus stage is Race to the Finish. It challenges the player to descend five floors and reach the exit, while avoiding explosives, bumpers, and some of the Fighting Polygon Team. Unlike the other bonus stages, the player has only one minute to complete the stage.
Stage 10: Fighting Polygon Team
Stage 11: Master Hand (Final Stage)
The final stage takes place at the Final Destination and pits the player against Master Hand. This stage stands out from most others in the game, as it can not be cleared by knocking the opponent out past the blast line, but only by reducing the opponent's stamina to 0 HP. Master Hand on all difficulties has 300 HP.
Upon clearing the 1P Game, the game gives the player a small reward: a static image featuring the character in a specific scene along with the announcer saying "Congratulations!". Most of these screens are entirely original images made for the game; the sole exception is Captain Falcon's, which was an unlockable title screen for F-Zero X. The announcer will also exclaim "Incredible!" if the player manages to score at least 1 million points and no miss 11 times by the end of the game.
The congratulations screens are present only in the American and PAL versions of the game, and not in the Japanese version.