Cosmos

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1.1.0 · Paper 26.3 / Folia 26.3

Cosmos adds a second dimension above your world: keep flying up and you break through into a silent starfield where every planet is generated from a coordinate hash. Fall back down and you return to where you left off.

Features

Feature	What it gives you
A sky full of planets	Every planet is generated from its coordinates and a seed, so the same seed always produces the same sky. Spheres of stone, sand, ice, basalt and more, each with a crust, a thicker shell and a solid core.
Y-axis travel	Fly past Y = 400 in the overworld to enter Cosmos; drop below Y = 0 in Cosmos to come home. No portals, no commands needed.
Scale that keeps you oriented	The two worlds share one horizontal map at 1:64 — x = 1600 in the overworld is x = 25 in Cosmos. Your position always maps back.
Low gravity, elytra-first	Falling is slowed to a gentle drift, and anyone wearing an elytra is left completely alone so gliding feels vanilla.
Floating items	Dropped items hang in space instead of dropping forever (experience orbs optional).
A landmark to land under	A guaranteed planet sits right above the arrival point, so stepping into the void is never a dead end.
Folia ready	Runs on both Paper and Folia, detected at runtime.

Requirements

• Paper 26.3 or Folia 26.3 (older 1.21.x servers work only with a jar built for their API version)
• Java 21 or newer on the server

Install

1. Drop Cosmos-1.1.0.jar into plugins/.
2. Start the server.
3. That's it — the cosmos world is created the first time someone travels there, or immediately with /cosmos reload.

Your first trip

1. Stand in the overworld and fly (or build) up to Y = 400.
2. You are moved to Cosmos at (x / 64, 10, z / 64) — right under the origin planet.
3. Look up: that planet is your landmark. Everything else is procedural sky.
4. To come back, drop below Y = 0 in Cosmos and you reappear at (x * 64, 390, z * 64).

A 3-second cooldown after each jump prevents bouncing back and forth, and the Cosmos world border always mirrors your overworld border.

On a 320-block-tall overworld the build limit is Y = 319, so reaching Y = 400 needs an elytra and fireworks. That is intentional — but you can lower teleport-y-world (for example to 330) if you prefer an easier trip.

Configuration

Two files, both in plugins/Cosmos/. Run /cosmos reload after editing; world-level settings (name, environment, seed) only apply to a world that is created afterwards.

config.yml — travel

Key	Default	Meaning
scale	64	Horizontal ratio between the worlds. 4 means Cosmos is 4× smaller.
main-world	world	The overworld name travel starts from.
teleport-y-world	400	Y in the overworld that sends you up to Cosmos.
teleport-y-cosmos	0	Y in Cosmos that sends you back down.
teleport-y-offset	10	Safety margin: you arrive at teleport-y-cosmos + offset and leave at teleport-y-world - offset.
teleport-cooldown-ms	3000	Ignore new jumps for this long after one.
portal-cooldown-ticks	100	Vanilla portal cooldown applied after travel.
y-check-interval-ticks	10	How often player heights are checked.
teleport-preload-radius	2	Chunks around the landing spot loaded before the jump (radius 2 = 5×5). 0 disables preloading.
fallback-location	cosmos 0.5 160 0.5	Where /cosmos tp puts players who have no position to map.

config.yml — the Cosmos world

Key	Default	Meaning
cosmos-world-name	cosmos	Name of the dimension's world folder. Change it to get a brand-new sky.
cosmos-world-environment	THE_END	World type; THE_END gives a dark, cloudless sky. Height limits follow the environment.
cosmos-biome	THE_END	Biome used everywhere.
cosmos-world-seed	1337	Seed of the world itself (terrain features, not planets).
cosmos-world-auto-create	true	Create the world automatically if it does not exist.
cosmos-world-border-sync	true	Mirror the overworld border into Cosmos at the chosen scale.
cosmos-world-gamerules	see file	Gamerules applied to Cosmos (mob spawning off, time running, weather frozen, fall damage on).
world-check-interval-ticks	100	How often the plugin looks for the world / border changes.
cosmos-view-distance	0	Simulation view distance for Cosmos. 0 keeps the server default; 6–8 makes dimension changes much lighter.
cosmos-send-view-distance	8	Chunks sent to the client in Cosmos. Lower = faster to enter and leave, but fog closer in.

config.yml — floating and low gravity

Key	Default	Meaning
item-float-enabled	true	Dropped items stop falling in Cosmos.
float-experience-orb	false	Also freeze experience orbs.
float-freeze-velocity	true	Stop items completely instead of letting them drift.
float-unlimited-lifetime	false	Keep floating items forever.
float-sweep-interval-ticks	200	How often the area around each player is re-checked.
float-sweep-radius	16	Radius of that re-check — dropped items inside it are re-applied the floating state.
player-float-enabled	true	Slow down falling in Cosmos.
player-float-fall-speed	0.08	Maximum downward speed while falling, in blocks per tick.
player-float-interval-ticks	2	How often that speed limit is applied.
player-float-skip-elytra	true	Leave players wearing an elytra alone — keep this on unless you want the slow fall to fight your glider.
debug	false	Extra log lines.

planets.yml — the starfield

Key	Default	Meaning
enabled	true	Turn all procedural planets off (the world becomes empty space).
cell-size	96	Size of the grid cell each planet is placed in. Smaller = denser sky.
chance	0.6	Probability that a cell holds a planet. Higher = denser sky.
min-radius / max-radius	6 / 28	Size range of generated planets.
min-shell-thickness / max-shell-thickness	2 / 8	Thickness of the crust between surface and core.
min-y / max-y	40 / 240	Height band for planet centres (clamped to the world's build range).
seed	20260101	Change it for a completely different sky.
spawn-planet	true	Keep one planet directly above the arrival point.
spawn-radius / spawn-center-y	42 / 60	Size and height of that landmark planet.
weight	0	Draw order when planets overlap.
palette	6 entries	Block pairs (outer-block / core-block) used to build planets; one is picked per planet.

Quick tuning:

• More planets — lower cell-size (e.g. 64) or raise chance (e.g. 0.8).
• Fewer, bigger planets — raise cell-size, raise max-radius.
• Different sky, same world — change seed.
• No landmark — spawn-planet: false.
• Empty space — enabled: false.

Commands and permissions

Command	Permission	Default	What it does
/cosmos reload (/cos reload)	cosmos.reload	op	Reload config.yml, planets.yml and message.yml.
/cosmos tp <player>	cosmos.tp	op	Send a player into Cosmos.
/cosmos info	cosmos.info	everyone	Show scale, thresholds and world status.

cosmos.admin grants all three. Every message (prefix, colours, wording) is editable in message.yml.

Troubleshooting

Symptom	Fix
Flying up does nothing	You must be in main-world and at or above teleport-y-world. Check /cosmos info.
I arrive in empty space	spawn-planet is off, or spawn-center-y puts the landmark out of reach — set spawn-center-y: 60.
Planets look sparse	Lower cell-size or raise chance; or pick a new seed.
The sky looks nothing like the screenshots	Chunks that already exist are never redrawn. Travel to new areas, or change cosmos-world-name for a fresh world.
Elytra barely works in Cosmos	Make sure player-float-skip-elytra is true (the default).
Client freezes when entering or leaving	Lower cosmos-send-view-distance to 6, and teleport-preload-radius to 0.
My old planets: list is ignored	Correct — hand-written planets were replaced by the procedural field. Delete the section.
Config edits do nothing	Run /cosmos reload; changing cosmos-world-name, environment or seed requires a new world.

Known limitations

• Planets are static solid spheres; they do not orbit or pull you in.
• Cosmos is a normal Bukkit world, so its height limit follows cosmos-world-environment (THE_END = 256 blocks). Planets that would stick out are flattened at the top.
• THE_END skies have no sun or clouds — that is the point, but it means no natural light source.
• Changing the environment or seed of an existing world is not supported; rename the world instead.

License

MIT © 2026 LiuyeStudio — see LICENSE.