Angle

The angle of an attack, also known as trajectory, is what direction it sends opponents when it connects, such as horizontally, vertically, or diagonally. Many attacks have multiple hitboxes that possess slightly (or even significantly) different angles, so opponents being hit by different parts of one attack can be sent in different directions. Angle is a basic property of all hitboxes that has a major effect on an attack's effectiveness as a whole.

The angle of a hitbox is defined as a number of s and can span any integer number, where 0 equals "away from the attacker", 90 equals "straight up", 180 equals "towards the attacker", and 270 equals "straight down"; negative angles such as -90 can also be used, and can carry an additional meaning depending on the game.

Types of angles
Generally, no one angle is better than any other; two otherwise identical attacks that have differing angles will often have different purposes. One of the most dramatic of these comparisons is in Melee: despite Fox's and Falco's Reflectors having very similar properties, and both being central to their characters, they have completely different usages in competitive play. A character that lacks a type of move within one of these broad classes (for example, a vertical KO move) will often be at a disadvantage compared to a character that has at least one of every option.
 * Attacks with vertical angles are suited for aerial combos and juggling, and are more effective at KOing characters near the top blast line, especially if they are floaty.
 * Attacks with diagonal angles can be used to set up tech-chases, especially on fast fallers or near platforms, and are more effective for KOing opponents near the horizontal blast lines, as well as getting them offstage for edgeguarding.
 * Attacks with almost purely horizontal angles, known as semi-spikes, are especially deadly as they leave opponents in a highly disadvantageous position to recover offstage, and can guarantee tech-chases onstage.
 * Downward angles, known as meteor smashes, are very dangerous against offstage opponents and usually efficient combo starters onstage, although these attacks can be meteor canceled in Melee and Brawl.
 * In Melee, an attack that sends opponents in a downward angle outside of the window between 260 and 280 degrees is called a spike; an attack with this angle functions similarly to a meteor smash, but the knockback cannot be meteor canceled, making it even more lethal offstage. In other games, all downward-angled attacks count as meteor smashes.

In all Smash games, moves that launch at angles between 70° and 110° put characters in a special hitstun animation (known as DamageFlyTop internally), which usually has them face upward, compared to moves that launch at other angles, which can induce up to three hitstun animations depending on the height they hit the character at. In most games, the difference between this animation and others is purely aesthetic; however, in Ultimate, it has a special effect, causing characters to use different falling speed and gravity values during knockback that are homogenized across the cast. As a result, vertical finishers in Ultimate KO most characters at roughly the same percentage, unlike in previous games, where their individual falling speed and gravity could greatly affect their vertical endurance (especially in Melee).

Angle flipper
Generally, the definition of "away" versus "towards" is based on where the attacker and the opponent are positioned, not the hitboxes and hurtboxes involved. In SSB and Melee, all attacks work this way, which results in some attacks being able to send opponents in unexpected directions; 's back air and 's Knee Smash in Melee are notable examples of cases where players intentionally try to land "reverse" hits for combo purposes. Likewise, throwing an item against an opponent too close to them might cause the hit to be registered from behind them, and thus launch them towards the attacker instead of away.

From Brawl onward, hitboxes can have a property known as an angle flipper set to them, which can determine whether the target is always set in the direction the attacker is facing (forward), or opposite to said direction (backward), among other variables. Otherwise, this direction is based on the attacker and target's positions as usual. In Brawl, angle flippers were mainly used for throws, grab related hitboxes and projectiles, although a few normal attacks also used them. In Smash 4, several more moves used angle flippers, namely various forward smashes always sending the target forward, and most back aerials always launching them in the opposite direction they were initiated. They are also present on almost all pummels and all edge attacks, which launch the target forward (this was also the case with pummels in Brawl). In Ultimate, angle flippers are even more widespread: all characters' entire neutral attacks, as well as almost all dash attacks, forward tilts, forward smashes, and forward aerials launch opponents forward, while all back aerials launch them backward (including those that did not in Smash 4); the only exceptions are, , and 's dash attacks, 's forward tilt and forward aerial, 's forward smash and forward aerial, 's forward aerial (except with Red Pikmin), and 's forward aerial.

Since angle flippers overall cause the behavior of a move's knockback to be more consistent, they tend to be beneficial for moves aimed on a specific direction. For example, forward tilts and forward smashes can ensure the opponent is sent in the desired direction and preserve the user's advantage state, instead of ending up in a position that is more difficult to capitalize on. On the other hand, they can be detrimental to certain moves with notable reach behind the user, such as Marth's forward aerial and Ike's forward smash, as the former's cannot be used for more unique followups if it hits from behind, while the latter is less effective for catching opponents near the edge attempting to jump over Ike. However, certain moves that hit around the user, more specifically multi-hitting ones, can benefit from angle flippers, allowing the user to more consistently determine the opponent's ending position after the final hit and either start and extend combos; notable examples of this are Bayonetta's Witch Twist, and 's neutral aerial in Ultimate.

Special angles
Certain angles are dynamic, changing the exact direction they launch based on additional factors.
 * In all games, the Sakurai angle (coded as a value of 361) changes from horizontal to diagonal as the knockback delivered increases. Sakurai angle moves start off as a straight 0° angle but as the knockback increases, the angle will eventually become more diagonal (how exactly it functions depends on the game).
 * In Melee, the Flipper uses the angle 362, which is directed from the point of impact to the center of the struck hurtbox. This means that it will usually knock the character directly away from the Flipper radially, though this can vary based on the exact motions and positions of the two. The angle is not used by anything else and has not reappeared in later games, though there is room for it to exist.
 * From Brawl onward, various autolink angles (coded as values from 363 to 368) match the direction and strength of knockback to the attacker's movements in an attempt to more consistently link multi-hit attacks together.
 * Starting from Brawl, moves which do not lift the opponent off the ground, and do not put them into tumble, will always keep the opponent in a grounded state. Additionally, if a move with a 0° angle deals greater than or equal to 32 units of hitstun, it will not send grounded opponents into tumble, despite dealing enough knockback to do so. The opponent will instead continue to slide along the ground, as they would if they had received fewer than 32 frames of hitstun, until either their momentum ends or they slide off a ledge/slide into the blastzone and get KOed.
 * In Ultimate, an angle of 0° changes to a 32° angle when the knockback dealt is greater than or equal to 120 units, similarly to the Sakurai angle in Smash 64, but occurring much later and remaining a semi-spike.
 * Notably, this effect does not occur for the angle of 180˚, which can cause certain anomalies, such as Octopus' release behaving differently on left facing walls than right facing walls. Additionally, the opponent is still forced off the ground and put into tumble, only to immediately collide with the ground when the knockback commences (much like how the 0° angle worked prior to Brawl).