Like previous games in the series, Final Fantasy X is presented in third person perspective, with players directly navigating the main character Tidus around the world to interact with objects and people. Unlike previous games, the world map and city map have been fully integrated, with the terrain outside of cities now rendered to scale. Upon encountering an enemy, the environment switches to a turn-based "battle arena" where characters and enemies must wait their turn to fight.
Players are again given the opportunity to advance and improve their characters by defeating their enemies and acquiring items, though the traditional experience point system has been replaced by a new system called the "Sphere Grid".
Final Fantasy X deviates from previous Final Fantasy games in its lack of an involved overworld navigation system (a.k.a. "world map"). In the resulting "field map", all game locations are physically contiguous and never fade out to an interactive overworld map. Additionally, regional connections are mostly linear, essentially forming a single path through the game's locations. Map Director Takayoshi Nakazato has explained that with Final Fantasy X he desired to forego the traditional World Map concept in favor of a more realistic approach, in-line with the realism afforded by the mechanics of the game's dominant 3D backgrounds (as opposed to that offered by pre-rendered backgrounds, which he refers to as "pseudo 3D environments). An airship becomes available late in the game with an overworld map represented by a point-and-click interface that allows the player to choose an area to instantly travel to. In order to return to the airship, players must access one of the many save points scattered throughout Spira. As a result of this configuration, players can eventually navigate Spira in a matter of seconds.
Final Fantasy X introduces the conditional turn-based battle system (CTB) in place of the series' traditional active time battle (ATB) system. The new design allows for players to take a more strategic approach to battles by allowing the player ample time to choose which action to take each turn. It also allows characters' and enemies' attributes to affect the number of turns they're allowed and the order that they occur. Further, the game provides a graphical timeline along the upper-right side of the screen, allowing the player to quickly determine which characters and enemies will be receiving turns next, and also determine how various actions taken will affect the subsequent order of turns.
Character-specific special abilities (known as "limit breaks" in Final Fantasy VII and Final Fantasy VIII, and "Trances" in Final Fantasy IX) reappear in Final Fantasy X under a new name, "Overdrives". In this new incarnation of the system, most of the techniques are interactive, providing options of fighting game-style button inputs or precise timing to increase damage. Furthermore, the game introduces Overdrive Modes, which allow the player to designate what action (receiving damage or status changes, slaying an enemy, being the only live character on the field, casting healing or offensive spells, stealing items, attacking or even simply taking a turn) causes the Overdrive meter to fill.
Final Fantasy X introduces a drastic overhaul of the summoning system employed in the previous eight games in the series. Instead of the desired summon appearing to perform a single action as was previously the case, summoned monsters in Final Fantasy X (called "aeons") arrive to take the place of the party in battle entirely, and for as long a duration as desired by the player.
The player acquires five mandatory aeons over the course of the game, and several additional aeons can be unlocked by completing various sub-quests. Aeons have their own stats, commands, special attacks, spells, and Overdrives, and can even be slain by the enemy. Aside from offering powerful attacks, they can also be employed to guard the party during battles against difficult bosses, as any damage received from the enemy while an aeon is present will be inflicted on the aeon instead of the party. Only Yuna can summon aeons, and although certain spheres and items can make them more powerful, the overall stats of a player's aeons are always directly proportionate to Yuna's own current stats.
Final Fantasy X's leveling system, the Sphere Grid, is unique in the RPG genre. Instead of characters gaining pre-determined stat bonuses at the transition to the next level, each character gains a "sphere level" after collecting enough ability points (AP). Sphere levels, in turn, allow players to move around the Sphere Grid, a predetermined grid of several hundred interconnected nodes consisting of various stat and ability bonuses. Items called "spheres" (obtained from defeated enemies, treasure chests, and event prizes) are applied to these nodes, unlocking its function for the selected character. In this way, the playable characters' development resembles a board game.
The Sphere Grid system also allows players to fully customize characters in contrast to their intended battle roles, such as turning the summoner/White Mage Yuna into a physical powerhouse and the swordsman Auron into a healer. The International and PAL versions of the game include an optional "Expert" version of the Sphere Grid; in this version, all of the characters start in the middle of the grid and may follow whichever path the player chooses. As a trade-off, however, the Expert grid has noticeably fewer nodes in total, thus decreasing the total statistic upgrades available during the game.
Weapon and Armor Customization
Many weapons and armor in Final Fantasy X have empty "ability slots", up to a maximum of four total. These can be filled by the expenditure of items. Customizations can increase the player's attributes, cause weapons and armor to inflict or defend against elemental damage and status effects, automatically cast certain spells or use certain items, increase the amount of experience points a character receives from/during battle, or even exceed the normal limits on damage, hit points, and magic points. Often, customization changes the name of the weapon or armor as well as its abilities.
Capturing Monsters and the Monster Arena
Using special weapons with the capture ability, the player can capture monsters and deposit them into the Monster Arena in the Calm Lands, up to a limit of ten of each monster. The player may return to the Monster Arena to battle captured monsters at any time for a small fee. For capturing various groups of monsters, for example, all the different monsters in a given region or species, the player is often rewarded with special items and the opportunity to battle unique creations of the Monster Arena owner. These creations, while similar in appearance to some of the ordinary monsters, are much more powerful; many are enormously more powerful than the end boss of the game. By defeating these monsters, one can obtain an effectively unlimited supply of rare items for use on the sphere grid, or for weapon or armor customization.
Learning Al Bhed
The Al Bhed speak their own language, created by the transposition of letters in English or kana in Japanese. Throughout the game, items called Al Bhed primers are scattered, each of which reveals the mapping of one letter. Some are in locations that a player can only visit once; if the primer is not noticed and picked up, the player will never have another chance to obtain it again. The game does contain a feature (Al Bhed compilation spheres) allowing a player to transfer the Al Bhed primers from one saved game to another, thus making it possible to construct a complete set even having missed a primer.
These are the only locations at which a game can be saved. Additionally, a save sphere restores all HP and MP and heals or resurrects the aeons. After certain events in the game, the player can also participate in blitzball or board the airship from the save spheres.