Terraria is a 2D sandbox game with gameplay that revolves around exploration, building, crafting, combat, survival, and mining, playable in both single-player and multiplayer modes. The game has a 2D sprite tile-based graphical style reminiscent of the 16-bit sprites found on the SNES. The game is noted for its classic exploration-adventure style of gameplay, similar to games such as the Metroid series and Minecraft.
The game starts in a procedurally generated world, with players starting out with basic tools and a non-player character (NPC) guide to get them started and bring their attention to aspects of the game and progression. The game's world is made up of several layers of tiles that players can interact with and modify. Many resources, such as metal ores, can be found while exploring caves. Players begin with low health and mana, which can be increased by finding and crafting specific items. Some resources may only be found in specific areas of the map, stored in common and rare containers, or dropped by certain enemies. Players use resources to craft new items and equipment. Different recipes require different resources and crafting stations. Several items in Terraria create complex crafting trees involving a large amount of items to create a single powerful piece of equipment.
Players can encounter many different types of enemies in Terraria, the occurrence of which depends on several factors including time, location, and random events. The game features an open-ended class system, primarily divided into melee, ranged, magic and summoner classes. Players may also battle bosses that utilize a number of different combat mechanics and can drop rare and valuable items. Bosses are summoned by using certain items or when certain criteria are met. The defeat of some bosses is directly tied to in-game progression, while others remain optional. Defeating the Wall of Flesh boss advances the game into "hardmode", which adds many new enemies throughout the world, as well as new NPCs and items. Like bosses, players can battle special enemies and mini bosses during invasions, in which enemies appear constantly and they either must be defeated or a certain amount of time must pass before the event ends. Terraria also features seasonal events which activate during certain periods of the real world calendar year, adding new enemies and content.
Terraria has support for mods, which is facilitated by the third-party tModLoader. It later received official support when it was released as free downloadable content alongside the "Journey's End" update on Steam in 2020. Mods for Terraria vary widely in their scope, content, and purpose. Some, such as Thorium and Calamity, add new content to the game, including new bosses, weapons, and biomes. Others, such as Overhaul, rework the mechanics of the game to provide players with a different experience. And additional ones, such as Recipe Browser, Veinminer, and Fargo's Mutant Mod, aim to improve quality of life by streamlining parts of the game.
