Schrodinger Blocks

Quantum blocks that exist in superposition until a player observes them.

Every quantum block shimmers between two states:

• its natural block, whatever was actually there (stateA), and
• a "could be anything" block (stateB), a full opaque cube picked deterministically
  from a safe-candidate set using the block's coordinates.

It flickers back and forth with a haze of portal particles. The moment any player gets a
clear, unobstructed line of sight to it, the wavefunction collapses. The block locks to
one of the two, and which one is decided purely by its coordinates, not by chance or
timing. Look away all you like; until someone actually sees it, it never settles.

Quantum blocks can be placed by command or appear naturally as the world generates,
scattered underground like a quantum ore.

What it does

• Natural-vs-random shimmer: each quantum block alternates between its real, original
  block and a deterministic "could be any safe block" pick. Same coordinates always
  yield the same pair and the same collapse outcome.
• Safe-candidate set: the random side (and the only blocks natural-spawn will convert)
  are full opaque cubes only. No slabs, stairs, glass, leaves, carpets, plants, tile
  entities, redstone-state blocks, pistons, spawners, bedrock, or infested blocks. The
  set is built once at startup by scanning the Material registry and removing a problem
  blacklist.
• Natural world-generation: freshly-generated chunks have a configurable chance to seed
  quantum blocks at a random spot within a Y range, but only where the natural block is
  itself a safe full cube. Honors the global cap. Main-thread only.
• Observation: detected with a real eye-to-block ray trace. The line of sight must be
  clear; a block in the way does not count.
• Collapse: locks to a deterministic, coordinate-seeded outcome (the same spot always
  collapses the same way), then leaves an ordinary block behind, with subtle particle
  and sound feedback and an action-bar message telling the observer what they forced
  into existence.
• Performance: only blocks within observe-range x 1.5 of an online player are
  processed each tick. Idle blocks sit on their natural state and cost nothing, so a
  world full of scattered quantum blocks looks untouched until a player is near. Then
  shimmering resumes.
• Persistence: still-unobserved blocks survive restarts. The natural state and seed are
  stored, so the pair and the outcome are unchanged.

Commands

| Command | Description |
|---|---|
| /quantum place [forcedStateB] | Make the block you are looking at quantum. stateA is that block's current type; stateB is the seeded safe-random block, or forcedStateB if you supply a material. |
| /quantum clear | Stop tracking the quantum block you are looking at (leaves the current world block as-is). |
| /quantum clear all | Stop tracking every quantum block. |
| /quantum info | Show active count and current tunables. |
| /quantum reload | Reload config.yml (admin). |

Aliases: /qblock, /superposition.

Permissions

| Permission | Default | Grants |
|---|---|---|
| quantum.use | op | Place and clear quantum blocks. |
| quantum.admin | op | Reload the config (implies quantum.use). |

Config (config.yml)

observe-range: 24.0              # eye -> block-centre distance that allows observation
shimmer-period-ticks: 4          # ticks between shimmer flips (20 = 1s)
max-active-blocks: 500           # safety cap on concurrent superpositions

natural-spawn:
  enabled: true                  # master switch for world-generation spawning
  chance-per-chunk: 0.12         # probability a fresh chunk gets any quantum block(s)
  max-per-chunk: 1               # max quantum blocks placed per new chunk
  min-y: -60                     # lowest Y a natural quantum block may appear at
  max-y: 64                      # highest Y a natural quantum block may appear at

There is no longer a default-state-a / default-state-b. The two states are now the
block's natural type and a coordinate-seeded pick from the safe-candidate set.

Reload at runtime with /quantum reload.

Compatibility

Paper / Spigot / Bukkit / Purpur 1.21.1 to 1.21.11 and the 26.1.x line (verified on
26.1.2), Java 21. Built against the Spigot API only (no Paper-specific classes), so the
same jar runs on any of them.

Original concept, an internal test idea, not sourced from a Reddit post.