# What the missions actually test — all 28 scripts surveyed

Status: ✅ corpus-wide counts, verified independently; ✅ two idioms identified
that change how the numbers read; 🟡 one built-in's semantics only partly read.

All 28 `Stage\StageNN.ssb` scripts decoded with `tools/re-capture/isl.py`:
**2,085,628 bytes, 25,705 built-in call sites, 108 of the 147 built-ins ever
used.** Nothing failed to parse. Re-checked here against the survey: `33=0`,
`34=0`, `108` distinct, `hp_pct_test` 1955, `unit_state` 1271 — all exact.

## ✅ The kill-counter primitives are DEAD, game-wide

`global_counter0` / `global_counter1` (built-ins 33/34) have **zero call sites in
all 28 stages**. Their handlers exist and are wired — they read
`[0x828F35C4]+8` and `+12` into the int result register — and **no mission ever
calls them**.

39 built-ins are never called at all, including `timer_start`,
`deploy_and_wait`, `camera_at`, `play_voice` and `screen_fade`.

### 🔴 CORRECTION: "no mission counts kills" was too strong

I wrote that here, and it is wrong as stated. What is true is narrower: **no
mission reads the two GLOBAL counters.** The game does track kills, and missions
do test them — through *attribution*, per unit and per squadron pair:

| built-in | what it is | sites |
|---|---|---|
| **105 `killed_by_player(unit)`** | reads `[squadron+600]`, which the unit-death handler sets from the damage message's `_BY_PLAYER` flag — "was the most recent death in this squadron the player's doing" | **117 across 14 stages** (S02: 38, S01: 32) |
| **72** | numerator is a per-`(killer, victim)` **squadron kill counter** incremented in the unit-death handler | 13, **S01 only** |

`killed_by_player` is the 17th-most-used built-in in Stage 02. So "did *the
player* get that kill" is a common mission predicate — the game simply never asks
"how many kills in total".

The evidence for 105 is the game's own strings: the death handler branches on
that flag into `"KILLED_BY_PLAYER"` versus `"KILLED"`, alongside
`LOST_TURRET_BY_PLAYER`, `SHIELD_DOWNED_BY_PLAYER`,
`DAMAGED_BY_PLAYER_GREATER_50` and the rest of the family.

## ✅ `hp_pct_test(unit, 0.0)` *is* a destruction test

**1786 of 1955 `hp_pct_test` calls (91 %) pass threshold `0.0`** — 107 of
Stage 02's 109 resolvable sites. Built-in 20's handler (`0x8226AB78`) explains
it: above zero it returns `pct ≤ threshold`, but at exactly `0.0` it takes a
separate path that *also* requires the unit's state field `[unit+16] == 4`.

So **`unit_state` and `hp_pct_test(…, 0)` are interchangeable "is it destroyed"
tests**, and stages simply pick an idiom. Real damage thresholds are the
minority: 50 (57×), 30 (19×), 70 (18×), 40 (14×), then a thin tail.

This matters for reading the counts: a stage with no `unit_state` is not
necessarily testing something different — S14 has none, and 25 of its 34
`hp_pct_test` calls pass `0.0`.

## ✅ `squad_survival_pct` is a boolean, not a percentage

29 sites, in S06/S07/S08/S09/S15, and **every one passes a friendly TCAF
squadron and the threshold 99.9**. The handler divides current by initial member
count with an **integer `divwu`** before multiplying by 100.0, so the value can
only be **100 or 0**.

At a 99.9 threshold that makes every site the predicate *"has this friendly
squadron lost anybody at all?"* — an escort-casualty test. **The game has no
"destroy N% of a squadron" objective.**

## ✅ The condition vocabulary, and the outliers

| pattern | stages |
|---|---|
| `unit_state` + `hp_pct_test` + `dist_lt` + `unit_relation` | the story stages |
| `squad_survival_pct` (escort intact?) | S06, S07, S08, S09, S15 |
| `group_ratio_pct` | **S01 only**, 13 sites, always `(TCN001, <ADAN squadron>)` |
| player gauges 132/133/134 | **S16 only** — 11 + 2 + 2 sites |
| `is_engaged` | **S05 only**, 3 sites, all on `TCN004` |

**S18–S23, the tutorials, are the outliers by a distance.** No flag/trigger
machinery at all — zero `read_freg`, `clear_flag`, `reset_phase_threads`
(built-in 100, formerly mis-named `push_trigger`),
`named_event`, `MARK_LAST_PHASE`, `FORCE_END_PHASE`, and none of the timer
family. One `set_flag` and one `END_PHASE` each. They are linear scripted
lessons, not missions.

**S16 has no unit predicates whatsoever** — its symbol table 2 holds three
entries, and its conditions are a descending player-gauge ladder
(75/50/25/10/0). A player-state set piece.

## 🟡 Not settled

* ✅ **`group_ratio_pct` (72) — read to the bottom, and the old label was wrong
  in the numerator.** It is
  `100 × (units of squadron B killed by squadron A) ÷ (declared member count of
  B)`, with a real `fdiv`. The numerator is `e[+12]` of a 16-byte entry in the
  table at `0x828F363C`, created by an interpreter command (max 32 entries) and
  incremented inside the unit-death handler as
  `(killer squadron id, victim squadron id)`. So it is **attributed kills, not
  survivors** — and it reads 0 unless the script first registered the `(A, B)`
  pair in `[phase+328]`. The name `group_ratio_pct` is retained but the
  "current ÷ initial members" gloss is **withdrawn**.
* ✅ **Built-in 55 is effectively dead**: **0 call sites corpus-wide**. It
  computes a component-count ratio by category (Bridge / Hatch / Turret /
  ShieldGenerator / Thruster / Versatile — names taken from the unit-`.tbl`
  loader's own `TurretCount`/`ShieldGeneratorCount` strings), but its numerator
  is a spawn-time snapshot nothing decrements, its category pairing is offset by
  one (slot 0's denominator absorbed `Hatch`), its k=5 denominator is never
  written, and it truncates with an integer `divw` before the ×100. Whether the
  misalignment is a shipped bug is **unknown**.
* ✅ **Built-in 75 is text** — five symbol-table-1 names resolved through a
  dictionary at `[phase+376]` into five 1024-wchar slots, which
  `sub_821AA1B0` copies into five 256-wchar HUD fields when `[phase+336] == 2`.
  Mechanism confirmed; **which** text (objectives, briefing, subtitles) is not.
  39 sites, 3 in Stage 02.
* `isl.py`'s `UNIT_ARG` omitted 71 and 72, so their second unit operand printed
  as a bare integer. Noted in the tool; 56 may be the same shape, unverified.
* The timer names in `isl.BUILTIN` look mismatched: 73 `timer_start` has **zero**
  sites while 123/124 carry the traffic, and their handlers are the run/stop
  pair. Flagged, not renamed.