Hytale Gravity Flip
Builder-friendly anti-gravity zones for Hytale servers.
Define a region with a wand, name it, walk on the ceiling — no code, no restarts.
---
## Showcase
Click to watch on YouTube
### Screenshots
---
## Features
- **Builder-first workflow** — define regions entirely in-game with a custom wand. No config editing required for the common case.
- **Six subcommands** — `wand`, `define`, `list`, `delete`, `toggle`, `tp`.
- **Per-UUID wand selection store** — each builder owns their own pair of corners; survives rejoin.
- **Persistent regions** — every zone serialised to `regions.json`, reloaded on boot via the Hytale `Config` API.
- **Two visualization modes** — `Outline` (AABB wireframe) and `Particles` (volumetric emitters on edges) with configurable color, opacity, refresh rate, and density. `None` for production.
- **Per-entity affect toggles** — target players only, items only, NPCs only, or any combination.
- **Configurable physics** — `VerticalForce` (lift strength) and `GracePeriodMs` (smooth entry transition) per region.
- **Optional fall-damage immunity** — suppress fall damage when leaving a zone so demos don't hurt.
- **Tick-loop detection** — efficient AABB containment check each tick (~100 ms), scales to dozens of active regions.
- **First-run bootstrap** — the plugin auto-seeds a demo region on first boot so the mechanic works out of the box.
---
## Quick Start
1. **Install** — drop `hytale-gravity-flip-.jar` into `/Server/mods/` and start the server.
2. **Get the wand** — run `/gravityflip wand` in-game. You receive the *Gravity Flip Wand* item.
3. **Pick two corners** — primary-click block A (pos1), secondary-click block B (pos2).
4. **Name the region** — `/gravityflip define my_zone`. Gravity inverts inside the box immediately.
5. **Fly up. Congratulations.**
---
## User Guide
### Commands
All commands are sub-commands of `/gravityflip`.
| Command | Description | Example |
| ----------------------------------- | -------------------------------------------------------------------------------------------- | -------------------------------- |
| `/gravityflip wand` | Gives the caller a *Gravity Flip Wand* item. | `/gravityflip wand` |
| `/gravityflip define ` | Creates a region from the caller's current wand selection (both corners required). | `/gravityflip define arena` |
| `/gravityflip list` | Prints every registered region with its AABB coordinates and enabled state. | `/gravityflip list` |
| `/gravityflip delete ` | Removes a region from disk and memory. | `/gravityflip delete arena` |
| `/gravityflip toggle ` | Enables or disables a region without deleting its config. | `/gravityflip toggle arena` |
| `/gravityflip tp ` | Teleports the caller to the center of a region (handy for large or hidden zones). | `/gravityflip tp arena` |
### The Wand
The *Gravity Flip Wand* is a custom item registered through Hytale's item asset pack and `Interaction.CODEC`.
- **Primary click** on a block → sets **pos1** (min corner candidate).
- **Secondary click** on a block → sets **pos2** (max corner candidate).
- Selection is stored **per player UUID** in an in-memory `WandSelectionStore`. Rejoining the server preserves the selection for the session.
- Once both corners are set, `/gravityflip define ` normalizes them into an axis-aligned `Box(min, max)` and persists the region.
### Region Anatomy
Every region is serialised to `regions.json` via `GravityFlipRegion.CODEC`. Only `Name` and `Box` are mandatory; every other field has a sensible default and can be omitted.
| Field | Type | Default | Description |
| ----------------------- | --------- | --------------- | ------------------------------------------------------------------------------------------------ |
| `Name` | string | *(required)* | Unique region identifier used by commands. |
| `Box` | AABB | *(required)* | Axis-aligned box `{ "min": [x,y,z], "max": [x,y,z] }`. Min must be component-wise ≤ Max. |
| `Enabled` | boolean | `true` | If `false`, the region is persisted but dormant (no detection, no visualization). |
| `FallDamage` | boolean | `false` | If `true`, vanilla fall damage is preserved. `false` suppresses fall damage on exit. |
| `GracePeriodMs` | integer | `2500` | Smooth entry transition window (ms). `0` = instant flip. |
| `VerticalForce` | double | `0.1` | Upward force applied per tick. Gentle lift ≈ `0.05`. Launch pad ≈ `0.3`. |
| `AffectPlayers` | boolean | `true` | Flip players inside the region. |
| `AffectNpcs` | boolean | `true` | Flip NPCs / mobs inside the region. |
| `AffectItems` | boolean | `true` | Flip dropped items inside the region. |
| `VisualColor` | string | `#00FFFF` | Hex color for the outline / particle tint. |
| `VisualMode` | string | `Outline` | One of `Outline`, `Particles`, `None`. |
| `VisualRefreshMs` | integer | `1000` | How often the visualization is re-emitted (ms). Lower = smoother, heavier. |
| `VisualOpacity` | double | `0.5` | Overlay opacity, `0.0`–`1.0`. |
| `VisualParticleId` | string | `Torch_Fire` | Hytale particle asset id used in `Particles` mode. `Dust_Sparkles_Fine` is invisible in-world. |
| `VisualParticleDensity` | double | `0.3` | Particles per edge unit. `1.0` saturates; `0.1` is sparse. |
### Visual Modes
- **`Outline`** — colored AABB wireframe, refreshed every `VisualRefreshMs`. Best for builders and debugging.
- **`Particles`** — particle emitters along the box edges, density and id configurable. Best for gameplay / showcase.
- **`None`** — region is invisible. Use in production once builders are done.
### Configuration File
The region file lives at `/Server/mods/Mythlane_GravityFlip/regions.json` and is written by the plugin whenever a command mutates the registry.
- **Hot-reload:** not currently exposed as a subcommand — restart the server (or reload the plugin host) after hand-edits.
- **Auto-save contract:** command handlers save immediately after mutations. External edits must restart.
- **First-run:** if `regions.json` is empty/missing, the plugin seeds one showcase region (`demo-gravity-flip`, box `(0,100,0)..(10,120,10)`, particles on).
---
## Showcase Regions
A set of curated regions ships with the dev server's `regions.json`. They collectively exercise every plugin capability. Spawn is `(0, 81, 0)` on a superflat surface.
| Region | Min | Max | What it demonstrates |
| -------------------------- | ---------------- | ----------------- | --------------------------------------------------------------- |
| `tutorial_walk_on_ceiling` | (10, 81, 10) | (15, 86, 15) | Baseline player-only flip with cyan outline. |
| `item_fountain` | (20, 80, 10) | (23, 100, 13) | Tall vertical zone, items only — drop stuff and watch it rise. |
| `mob_chamber` | (30, 81, 10) | (40, 89, 20) | NPC-only flip with red outline. |
| `full_chaos` | (-15, 81, 10) | (0, 91, 25) | Players + NPCs + items, purple particles. |
| `gentle_lift` | (-40, 80, -20) | (-20, 85, 0) | Soft `VerticalForce=0.05` — slow drift. |
| `strong_launch` | (-15, 80, -15) | (-10, 83, -10) | Aggressive `VerticalForce=0.3` — launch pad. |
| `grace_period_demo` | (15, 81, -20) | (23, 87, -12) | `GracePeriodMs=5000` — smooth fade-in. |
| `no_grace` | (25, 81, -20) | (33, 87, -12) | `GracePeriodMs=0` — instant flip, side-by-side comparison. |
| `fall_damage_off` | (40, 110, 0) | (50, 120, 10) | Elevated zone with `FallDamage=false` — safe exit. |
| `disabled_example` | (-30, 81, 0) | (-25, 86, 5) | `Enabled=false` — persisted but inert, proves state handling. |
| `showcase_arena` | (-80, 81, -80) | (-50, 96, -50) | 30×15×30 gold-outlined arena — hero shot for video. |
| `dense_particles` | (50, 81, 50) | (58, 89, 58) | `VisualParticleDensity=1.0` — maxed visual saturation. |
---
## Installation
```bash
# 1. Build the plugin jar
./gradlew clean shadowJar
# 2. Copy the fat-jar into your Hytale server's mods folder
cp build/libs/hytale-gravity-flip-*.jar "/Server/mods/"
# 3. (Re)start the server — the plugin auto-registers its item, interaction, and tick loop.
```
On first boot the plugin creates `Server/mods/Mythlane_GravityFlip/regions.json` and seeds a demo region. Edit in-game via commands, or hand-edit the file and restart.
---
## Development
### Prerequisites
- **JDK 25** (toolchain enforced by Gradle).
- **Hytale Plugin API** — pulled from `https://maven.hytale.com/release` as `com.hypixel.hytale:Server`. Version pinned via `hytaleServerVersion` in `gradle.properties`.
- A local Hytale dev server (for the optional `copyJarToDevServer` deploy task).
### Project Structure
```
src/main/java/com/mythlane/gravityflip/
GravityFlipPlugin.java # Entry point (setup / start / shutdown lifecycle)
command/ # /gravityflip root + 6 sub-commands
config/ # GravityFlipConfig — persisted region list codec
region/ # GravityFlipRegion, RegionRegistry, RegionSnapshot
wand/ # WandSelectionStore + Interaction (CODEC-registered)
tick/ # RegionTickLoop — per-tick AABB detection
physics/ # GravityApplier, FallDamageGuard, FallDamageSuppressorSystem
viz/ # RegionVisualizer + ParticleEdgeEmitter
src/main/resources/
manifest.json # Hytale plugin manifest (filtered by processResources)
Server/Item/Items/
gravityflip_wand.json # Custom wand item asset
Server/Interaction/RootInteractions/
gravityflip_wand_root.json # Wand root interaction definition
src/test/java/... # JUnit 5 unit tests (pure-data stores, codec round-trips)
docs/screenshots/ # Portfolio assets
```
### Build
```bash
# Fat-jar (shadow) with gson relocated to com.mythlane.gravityflip.libs.gson
./gradlew clean shadowJar
# Run tests
./gradlew test
# Build + auto-deploy to the configured dev server
./gradlew shadowJar
# The shadowJar task is finalized by copyJarToDevServer, which copies to:
# C:/Users/minit/Desktop/HYTALE SERVER/Server/mods (default)
# Override with: -PdevServerMods= or set in gradle.properties
# Disable with: -PdevServerMods=disabled
```
### Extending the Plugin
Adding a new subcommand is three lines:
```java
// In GravityFlipCommand.java
this.addSubCommand(new GravityFlipMySubCommand(plugin));
```
Adding a new wand-triggered interaction: register an additional `Interaction.CODEC` entry in `GravityFlipPlugin#setup()` and reference it from your item's `Interactions` block in `src/main/resources/Server/Item/Items/- .json`.
Adding a new region field: append a `KeyedCodec<>` entry to `GravityFlipRegion.CODEC` with a setter/getter pair. Absence in existing `regions.json` preserves the Java default (no migration needed).
---
## Architecture
```
+-----------------------+ +--------------------------+
| Player / NPC / Item | | regions.json (Config)|
+-----------+-----------+ +-------------+------------+
| |
| per-tick AABB check | loaded at start()
v v
+-------+--------+ +--------+---------+
| RegionTickLoop | <------------ | RegionRegistry |
+-------+--------+ +------------------+
|
| entity in enabled region?
v
+-------+---------+ +-------------------+
| GravityApplier | ----> | y-velocity invert |
| + FallDamageGrd | | + fall-dmg guard |
+-----------------+ +-------------------+
Wand flow (independent, command-driven):
Player primary/secondary click
|
v
GravityFlipWandInteraction (Interaction.CODEC registered)
|
v
WandSelectionStore (keyed by UUID)
|
v (on /gravityflip define )
RegionRegistry.add(...) -> configHolder.save()
```
Key technical notes:
- **Plugin entrypoint** (`GravityFlipPlugin`) owns the lifecycle and all singletons. Wand interaction and item codec are registered in `setup()`; tick loop and command registry are wired in `start()`.
- **Persistence** uses `Config` from the Hytale core API — typed JSON codec, atomic save semantics. The `get()` call is deferred past `setup()` because it blocks on `preLoad()`.
- **Tick loop** runs every ~100 ms with a 2 s startup delay to let `Universe.get()` settle. `World` is resolved lazily each tick, so the tick is a no-op until the world is ready.
- **Wand interaction** is registered through `Interaction.CODEC` under the key `"GravityFlipWand"`, matching the `gravityflip_wand_root.json` root interaction that the item references.
- **Asset pack** is bundled inside the jar (`IncludesAssetPack: true` in `manifest.json`) and includes the wand model, icon, interaction root, and item definition.
- **Concurrency** — `Config#get()` returns a shared mutable reference; `RegionRegistry` snapshots it into an `AtomicReference` for lock-free tick-loop reads.
---
## Tech Stack
- **Java 25** — modern records, pattern matching, sealed types.
- **Gradle 8 + `com.gradleup.shadow` 9.3.1** — fat-jar build with gson relocation.
- **Hytale Plugin API** (`com.hypixel.hytale:Server`) — `JavaPlugin`, `Config`, `Interaction.CODEC`, `BuilderCodec`, `KeyedCodec`, `Universe` / `World` access.
- **Gson 2.10.1** — relocated under `com.mythlane.gravityflip.libs.gson` to avoid classpath clashes.
- **JUnit 5.10** — pure-data unit tests for selection store and codec round-trips.
---
## Roadmap
**v1** — **shipped** — custom wand, 6 subcommands, outline + particle visualization, per-region physics tuning, per-entity affect toggles, JSON persistence, first-run bootstrap, dev-server auto-deploy task.
**v2 — planned:**
- Hot-reload subcommand (`/gravityflip reload`) without restart.
- HUD indicator when entering/leaving a zone.
- Border visualization improvements (antialiased, beveled corners).
- Multi-world support (regions keyed by world id).
- Custom gravity profiles per region (horizontal push, directional gravity, zero-G).
- Import / export region sets as shareable JSON bundles.
- Permissions integration (who can create / edit / delete).
---
## Credits
Built by the **[Mythlane](https://mythlane.com)** team.
Plugin structure and conventions informed by the `VotePipe` and `myth_*` Hytale plugin family (Kotlin/Java scaffolding, CamelCase manifests, `gradle.properties` versioning).
---
## License
License TBD. Contact **socials@mythlane.com** for usage inquiries.
