# The throttle is a TARGET-SPEED selector — measured against the definition (2026-08-13)

**Status: ✅ for the shape of the law, 🟡 for the unit scale.**

The unit definition gives `MinimumVelocity 100`, `CruisingVelocity 350`,
`MaximumVelocity 1200`, `Acceleration 600` and `Deceleration 500` for
`UN_f001_TCAF_DeltaSaber_T_Player` ([values](captures/unit-runtime-fields.csv)),
but not **how** the game applies them. This measures it.

Method — [`tools/re-capture/speed_law.py`](../../tools/re-capture/speed_law.py):
lock onto the player entity once, then sample its own position triple in guest RAM
while holding each throttle input in turn (8 s per phase, 20 Hz). Speed is
differentiated over **1-second windows**, never per sample.

## Result

| phase | measured speed (1 s windows) | settles to | definition field |
|---|---|---|---|
| no throttle | 367 403 471 365 463 463 365 | **~420** | `CruisingVelocity` 350 |
| `RT` held | 1041 1376 1551 1379 1596 1510 1620 | **~1 530** | `MaximumVelocity` 1200 |
| release | 1314 672 432 452 432 450 408 | back to **~440** | — |
| `LT` held | 203 121 135 121 115 146 122 | **~125** | `MinimumVelocity` 100 |
| release | 369 451 427 425 445 390 465 | back to **~430** | — |

So the throttle **selects a target speed** — minimum / cruise / maximum — and the
craft converges to it; releasing either trigger returns it to cruise. It is not a
force model with the throttle adding thrust, which is what a reimplementation would
most likely have assumed from `Acceleration`/`Deceleration` alone. Those two fields
govern the **convergence rate**: the release phase falls ~1 314 → ~432 in about two
seconds (~440 units/s², against `Deceleration` 500) and the `RT` phase climbs ~420 →
~1 550 in two to three seconds (~470–560 units/s², against `Acceleration` 600).

## 🟡 The unit scale

Measured world-space speeds run **≈1.2–1.3× the definition numbers** in all three
regimes (cruise 1.21, maximum 1.28, minimum 1.32). The HUD, meanwhile, reads
**350** at cruise — the definition value exactly. So the definition's velocity unit
is the HUD's, and entity world coordinates are a constant multiple of it, close to
**1.25**. The spread across regimes is larger than the constant itself is precise,
because the craft is manoeuvring under fire while sampled (straight-line
displacement per window under-reads a curving path), so this is recorded as a
measured range rather than a pinned constant.

## Traps

* **`RT`/`LT` are analogue triggers**, so `vgamepad trig RT 1.0` holds the throttle;
  the button verb `hold RT` is a **silent no-op**. The first run of this probe
  measured the drift of a craft nobody was flying.
* **Do not differentiate per sample.** The guest updates the position slower than
  20 Hz, so per-sample differences alternate between 0 and a double step —
  `0, 1519, 1985, 0, 2681…` for a craft flying smoothly.
* **Bind late, measure fast.** The player entity is not in the typed-entity scan
  for the first ~15 s of a mission, and the craft dies within a few minutes if
  nobody is flying it — one earlier attempt ended at `GAME OVER` mid-probe.

Raw samples: [`captures/speed-law-throttle-phases.csv`](captures/speed-law-throttle-phases.csv).