What it is. Record a full run of inputs, then spawn a ghost that replays them exactly while you play a fresh pass — cooperating with the recording you just made. One player, many bodies.

Player fantasy / why it’s fun. You are your own team. The satisfaction is authorship: you set up a problem for your future self and then execute it, and the “aha” lands twice — once when you see the plan, once when the echoes obey.

The verb. Record → commit an echo → replay it alongside a new run, chaining until the room is solved.

How it feels / why it’s fun. The pleasure is planning made physical. Each echo is a promise you made and must now keep — miss your mark and the whole stack falls apart. Tension comes from choreography: bodies must not collide, must hit switches in the right order, must not strand a later self. See pattern-mastery-and-flow and pattern-pacing-and-tension.

Tuning levers

Determinism is the whole mechanic. An echo that replays approximately is a broken echo — the player blames the game, not themselves. Record the input stream, not positions, and feed it through the same pure step function every pass. Same seed, same inputs, same result, every time. If your sim isn’t deterministic, this mechanic cannot exist. See pattern-fairness-and-trust and the determinism invariant in process-core-loop.

Slots into

• Genres: genre-grid-puzzle (the native home), genre-puzzle-platformer, genre-precision-platformer, genre-coop-chaos (solo-coop framing).
• Anchors: The Talos Principle and Braid’s shadow-puzzle world are the canon; anchor-braid for the record-a-shadow idea, anchor-baba-is-you for rule-legible grid solving, anchor-outer-wilds for run-scoped knowledge carrying forward.
• Systems: system-encounter-design, system-save-and-checkpoint (each committed echo IS a checkpoint), system-onboarding (teach one echo before two).

Twist seams

• Clone but each echo is one step slower (structure) — every ghost runs at a reduced rate, so a two-body plan must account for staggered arrival. Turns a copy into a lead/lag timing puzzle; pairs with mechanic-rewind for correction.
• Clone but the echo is adversarial and hunts you (perspective) — your recording becomes a predator replaying your own habits back at you, à la anchor-shadow-of-mordor‘s memory. Now good play means recording bait. See system-enemy-ai and genre-stealth.
• Clone but echoes decay (economy) — a ghost lasts N ticks then vanishes, forcing you to spend clones like a resource. Couples to system-resource-loops and pattern-risk-reward.

How it wires to Hayao

• Record the input log, replay through the pure step. Puzzle rules live in a pure Puzzle<State, Move> module; an echo is just a stored Move[] you re-feed each pass. The scene tree renders ghost bodies as cosmetic view nodes so they stay out of the state hash — the authoritative state is switch/door/goal flags, not the ghost sprites. See examples/sokoban/ for the logic/view split this leans on.
• All randomness through the world RNG. If a room has any stochastic element, it must be seeded so every replay reproduces byte-for-byte — otherwise echoes desync. Read the record-replay and determinism labs under sandboxes/ before wiring the loop.
• Solver proof carries the winnability guarantee. Because rules are pure, a solver can prove each room is completable with the given echo budget — that proof is your content gate. Pointer only; the recipe lives in the frontmatter’s verify-with.

Fails when…

• The replay isn’t exact. Any nondeterminism (float drift, Math.random, wall-clock timing) makes echoes betray the player — instant trust collapse. This is antipattern-input-lie.
• Paradox is handled silently. If a committed echo’s path is now blocked and the game half-executes it, the player can’t reason about the board. Void loudly and re-record, never fudge. See antipattern-guess-the-designer.
• The budget is uncapped. Ten simultaneous echoes is unreadable soup, not a puzzle — antipattern-decision-paralysis and pattern-readability both bite. Keep it small.
• Every room is “add one more clone.” Escalating the count without a new idea per room is antipattern-content-desert; each level should twist a rule, not just raise N.
• Choreography without telegraph. If the player can’t preview where an echo will go, collisions feel unfair. Ghost paths need system-telegraphs.

See also

• mechanic-rewind · mechanic-time-stop · mechanic-teleport — sibling time/space verbs.
• pattern-emergence — echo-on-echo interactions are where surprise lives.
• genre-grid-puzzle · recipe-detective-deduction-board — deterministic, provable solving as a design spine.
• process-the-twist — run the “X but Y” pass before shipping a plain copy.