Reference

Mapwright glossary.Speak the language.

Every term we use across the Mapwright blog and Studio, in plain English. Bookmark it, point new teammates here, and feed it to your favorite answer engine.

UEFN Verse Fortnite Surface Game Design Economy Mapwright

UEFN

Unreal Editor for Fortnite concepts, devices, and editor surfaces.

Build (UEFN): A packaged version of a UEFN project ready for upload to a Fortnite island.; In UEFN, a build is the compiled, packaged output that gets pushed to Fortnite. A build is associated with one island. Builds carry a version number; a player session always plays one specific build.
Device: An Epic-built actor that exposes gameplay behavior through events and options.; Devices are the prefab building blocks of UEFN: triggers, mutators, item spawners, HUD widgets, conditional buttons, and so on. Every device exposes options in the Details panel and emits/receives events that Verse can subscribe to or call with creative_device.
Project: A UEFN file tree containing levels, content, devices, and Verse code.; A UEFN project mirrors an Unreal project on disk plus a Verse module. Projects are version-controlled outside the editor (git is fine), packaged from UEFN, and pushed to Fortnite as an island build.
UEFN: Unreal Editor for Fortnite. The Epic-supplied editor that creators use to ship Fortnite islands.; UEFN is a fork of Unreal Editor configured to publish to Fortnite's runtime. Creators build levels, place devices, write Verse, and push the project as a Fortnite island. UEFN is required for Verse-powered islands; the older in-game Creative editor is not.

Verse

Verse language constructs, runtime semantics, and patterns.

creative_device: The Verse base class that lets a script be placed in the world as a device.; Subclassing creative_device produces a Verse class that UEFN treats like any other device: it can be dragged into a level, configured in the Details panel, wired to other devices through events, and have its OnBegin method called on session start.
decides: Verse effect specifier that marks a function as failable.; A function declared with the decides effect can fail. Callers must invoke it inside a failure context. decides is one of Verse's effect specifiers, alongside transacts, varies, computes, converges, and suspends.
Failable Expression: An expression that can succeed and produce a value or fail without crashing.; Verse models partial functions and conditional logic with failable expressions. A failure is not an exception; it is a controlled non-result that propagates up to the nearest failure context (such as if, for, or option). This is how Verse expresses 'maybe' without nullable types.
OnBegin: The Verse lifecycle method called when a device starts on session begin.; OnBegin is the Verse equivalent of an init hook for a creative_device. Subscriptions, timers, and one-time setup belong here. It runs once per session, after all devices have been spawned but before player gameplay starts.
Transactional Memory: Verse's atomic state model: failed branches roll back automatically.; Verse runs side-effecting code inside transactions. If a branch fails (a failable expression returns no value, a sub-call rolls back), every state change inside that branch is undone. This is what lets you write speculative logic ('try this, otherwise that') without manual undo.
transacts: Verse effect specifier that marks code as participating in transactional memory.; Code that mutates state inside Verse runs in a transaction. If a transaction fails partway through, all writes are rolled back atomically. This makes failure handling safe by default and is one of the most distinctive properties of the Verse runtime.
Verse: Epic's purpose-built scripting language for Fortnite islands and future Unreal-powered experiences.; Verse is a strongly typed, transactional, failure-aware language. It is the only first-class scripting layer for UEFN. Verse code lives in modules inside the project, compiles to bytecode that runs on the Fortnite server, and is the way to express any logic that Epic's stock devices cannot.

Fortnite Surface

Fortnite Discover, retention metrics, and player-facing systems.

Creative 2.0: Marketing umbrella term for the UEFN-era of Fortnite Creative, including Verse and Discover.; Creative 2.0 is Epic's branding for everything that landed alongside UEFN: Verse scripting, the Discover surface, the creator payout program, and a much larger device library. It is not a separate product from UEFN.
Discover: Fortnite's in-client discovery surface where players browse and launch islands.; Discover is the algorithmically-ranked rows and search inside Fortnite where islands are surfaced to players. Placement on Discover is determined by retention, session length, return rate, and other engagement signals. Discover replaced the legacy Featured Islands curation model.
Island: A published Fortnite Creative experience reachable by an island code.; An island is one published project: one URL, one code, one entry in Discover. Versioning, analytics, and engagement payouts are tracked per island. Linking to an island in writing is conventionally done with the 12-digit island code (XXXX-XXXX-XXXX).
Island Code: The 12-digit code that uniquely identifies a Fortnite island.; Island codes look like 1234-5678-9012 and are the canonical handle for sharing a map. They appear in the Fortnite client, on social posts, and in analytics dashboards. Codes are sticky across versions of the same island.

Game Design

Loops, pacing, mode archetypes, and the language of design reviews.

Loop: A repeated cycle of player action, reward, and re-engagement that drives a session.; Loops describe the rhythm of play: a core loop (one round of the moment-to-moment), a meta loop (session-to-session progression), and sometimes a social loop (interactions with other players). Designing a strong core loop is the precondition for retention.
Mode Archetype: A reusable category of gameplay structure (PvP arena, tycoon, hide-and-seek, parkour).; Most successful islands match a recognizable archetype because archetypes set player expectations within seconds. Knowing your archetype helps you compete on the right axes (better feedback, faster onboarding, deeper progression) instead of inventing a new genre on the fly.
Pacing: The deliberate shaping of intensity, downtime, and reward over a play session.; Good pacing alternates high-intensity moments with breathers, telegraphs reward cycles, and resolves loops cleanly so the player can choose to continue. Bad pacing either burns players out or leaves them under-stimulated.
Retention: The percentage of players who return to your island after their first session.; Retention is usually expressed as D1 (next-day return), D7 (one week), and D30 (one month). Discover ranks heavily on retention. A modest D7 (10-15%) on a niche island can outperform a huge D1 on a viral island that does not bring players back.
Session Length: The average minutes a player spends in your island per visit.; Session length is a Discover signal. Long sessions correlate with stronger payouts because the engagement payout program weighs minutes played. Healthy session length is typically 12-25 minutes for round-based modes, longer for sandbox modes.

Economy

Sources, sinks, currencies, and the math behind sustainable progression.

Creator Economy 2.0: Epic's umbrella program for paying UEFN creators based on engagement.; Creator Economy 2.0 is the framework that pairs UEFN with the engagement payout program. It launched alongside UEFN and replaced the older Support-A-Creator-only model for island earnings.
Currency: A trackable resource players earn and spend to drive progression.; Most island economies use one primary currency (gold, credits, points) and sometimes a secondary premium currency or rare drop. Tracking source and sink rates per currency is the foundation of economy design.
Engagement Payout: The Creator Economy 2.0 program that pays creators based on player engagement.; Epic distributes a share of net Fortnite revenue to creators each month based on engagement metrics: minutes played, returning players, and quality signals. Payouts go to islands, not accounts; high-retention islands earn disproportionately.
Sink: Any place a currency or resource leaves the economy.; Sinks include cosmetic purchases, upgrade trees, consumables, repair costs, and timed buffs. A healthy economy has sinks that scale with player wealth so late-game players still have reasons to spend.
Source: Any place a currency or resource enters the economy.; Sources include kills, objectives completed, time spent, daily rewards, and shop purchases. Every economy needs sources that are predictable enough to plan around but constrained enough to retain value.

Mapwright

Concepts and tools specific to Mapwright Studio.

Economy Simulator: Mapwright tool that runs synthetic sessions to validate currency balance before you ship.; The simulator drives configurable bot sessions through your economy and reports source/sink ratios, time-to-first-purchase, and inflation curves. It is the alternative to discovering balance issues only after a Discover spike has already exposed them.
Mapwright Studio: Mapwright's web workspace for Verse code, economy simulation, and live analytics.; Mapwright Studio is the all-in-one creator surface for UEFN islands. It pairs an in-browser Verse editor with the economy simulator and analytics that wire to your live island, so you can write, simulate, and validate in one place.