refactor(h3d-carve-1): extract pure geometry helpers to src/geometry.js

Moves 7 exports from screen.js to a new ES module src/geometry.js:
  geoFretX (was fretX, now 2-arg), dZ, slideTrailEnd, camBaseDistU,
  camLowFretPullbackU, computeBPM, _makeGaussTex.

Internal helpers _fretXLog / _fretXUniStep / _fretXUni are module-private
inside geometry.js. Module-level constants (SCALE, K, FRET_SCALE, NFRETS,
FRET_SPACING_*, TS) are duplicated at geometry.js module scope — values
are compile-time and never vary at runtime.

screen.js keeps a 1-arg delegator (1 beyond-subst):
  const fretX = f => geoFretX(f, _h3dFretUniform);
No call site changes; fretMid / fretColumnWorldW / slideOffsetWorldX /
_recomputeFretSpacingDerived stay in screen.js and use the delegator.

Tests:
- highway_3d_geometry.test.js: class-killer via import() with 9
  known-answer assertions (geoFretX uniform/log invariants, dZ linearity,
  slideTrailEnd, computeBPM BPM estimate).
- highway_3d_fret_spacing: test updated to match delegator pattern + adds
  GEOMETRY_JS read to verify geoFretX export.
- highway_3d_sustain_bloom: retargeted _makeGaussTex check to GEOMETRY_JS
  (definition moved); call-site check stays on SCREEN_JS.
- highway_3d_panel_controls: vm loader strips ES import line and injects
  geometry stubs; all factory-statics tests unaffected.

Suite: 169/169 pass
  node --test tests/js/highway_3d*.test.js plugins/highway_3d/tests/*.test.js
Version bump: 3.35.0 -> 3.36.0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014uZ169yfoFYArXz962g7KW

plugins/highway_3d/plugin.json

@@ -1,7 +1,7 @@
 {
     "id": "highway_3d",
     "name": "3D Highway",
-    "version": "3.35.0",
+    "version": "3.36.0",
     "type": "visualization",
     "scriptType": "module",
     "bundled": true,

plugins/highway_3d/screen.js

@@ -6,6 +6,8 @@
 // main player and per-panel in splitscreen without any architectural
 // changes.
 
+import { geoFretX, dZ, slideTrailEnd, camBaseDistU, camLowFretPullbackU, computeBPM, _makeGaussTex } from './src/geometry.js'; // h3d-carve-1
+
 (function () {
     'use strict';
 
@@ -1510,22 +1512,11 @@
      *  Pure helpers
      * ====================================================================== */
 
-    // Logarithmic spacing — mirrors real guitar fret geometry (12th root of 2).
+    // _fretXLog, _fretXUniStep, _fretXUni — moved to src/geometry.js (h3d-carve-1).
-    const _fretXLog = f => {
-        if (f <= 0) return 0;
-        const raw = FRET_SCALE - FRET_SCALE / Math.pow(2, f / 12);
-        if (f <= FRET_SPACING_ANCHOR_F) return raw;
-        const rawAnchor = FRET_SCALE - FRET_SCALE / Math.pow(2, FRET_SPACING_ANCHOR_F / 12);
-        return rawAnchor + (raw - rawAnchor) * FRET_SPACING_STRETCH_ABOVE12;
-    };
-    // Uniform spacing — same column width per fret (chart-format style).
-    // Total board width equals the logarithmic NFRETS position for consistency.
-    const _fretXUniStep = _fretXLog(NFRETS) / NFRETS;
-    const _fretXUni = f => f <= 0 ? 0 : f * _fretXUniStep;
 
     let _h3dFretUniform = true;
     try { _h3dFretUniform = localStorage.getItem('highway_3d.fretSpacing') !== 'logarithmic'; } catch (_) {}
-    const fretX = f => _h3dFretUniform ? _fretXUni(f) : _fretXLog(f);
+    const fretX = f => geoFretX(f, _h3dFretUniform); // h3d-carve-1: delegator (1 beyond-subst)
 
     window.h3dSetFretSpacing = mode => {
         // Validate against the two supported modes before persisting so an
@@ -1568,24 +1559,9 @@
         const m = w / _fretLabelScaleRefW;
         return Math.max(0.32, Math.min(1.45, m));
     }
-    const dZ = dt => -dt * TS;
+    // dZ — moved to src/geometry.js (h3d-carve-1).
 
-    /**
+    // slideTrailEnd — moved to src/geometry.js (h3d-carve-1).
-     * Pitched slide uses `sl`, unpitched uses `slu` (slide-to vs unpitched slide fields).
-     * Prefer `sl` when both are present — matches RS wire.
-     * @returns {{ endFret: number, unpitched: boolean } | null}
-     */
-    function slideTrailEnd(n) {
-        const sl = n.sl;
-        const slu = n.slu;
-        if (Number.isFinite(sl) && sl >= 0) {
-            return { endFret: sl | 0, unpitched: false };
-        }
-        if (Number.isFinite(slu) && slu >= 0) {
-            return { endFret: slu | 0, unpitched: true };
-        }
-        return null;
-    }
 
     /**
      * Lateral slide offset along the fretboard during sustain — easing
@@ -1605,15 +1581,7 @@
         return (endX - startX) * w;
     }
 
-    // Camera tgtDist building blocks. Both the dynamic (camera-follow)
+    // camBaseDistU, camLowFretPullbackU — moved to src/geometry.js (h3d-carve-1).
-    // and locked (frets 1-12) branches compose tgtDist from these, so
-    // any future tuning of the base zoom curve or low-fret pullback
-    // lands in both branches without drift.
-    //   span    — camDistMax - camDistMin in fret-span units
-    //   minFret — lowest fretted note in the camera window (or 1 for
-    //             the locked branch, which assumes nut chords)
-    const camBaseDistU = span => 65 + Math.max(span, 4) * 3;
-    const camLowFretPullbackU = minFret => Math.max(0, 5 - minFret) * 4;
 
     // World-units-per-fret near mid-neck. Used by the camera-X hysteresis
     // gate (issue #34) to convert a fret-equivalent dead zone into world
@@ -1632,52 +1600,7 @@
         FRET_WIDTH_MID = fretX(7) - fretX(6);
     }
 
-    function computeBPM(beats, t) {
+    // computeBPM, _makeGaussTex — moved to src/geometry.js (h3d-carve-1).
-        if (!beats || beats.length < 2) return 120;
-        let lo = 0, hi = beats.length;
-        while (lo < hi) {
-            const mid = (lo + hi) >> 1;
-            if (beats[mid].time < t) lo = mid + 1; else hi = mid;
-        }
-        let closest = lo;
-        if (lo === beats.length) closest = beats.length - 1;
-        else if (lo > 0 && Math.abs(beats[lo - 1].time - t) < Math.abs(beats[lo].time - t)) closest = lo - 1;
-        const start = Math.max(0, closest - 2);
-        const end = Math.min(beats.length - 1, closest + 2);
-        let sum = 0, count = 0;
-        for (let i = start; i < end; i++) {
-            const dt = beats[i + 1].time - beats[i].time;
-            if (dt > 0) { sum += dt; count++; }
-        }
-        return count > 0 && sum > 0 ? 60 / (sum / count) : 120;
-    }
-
-    // Build a horizontal gaussian DataTexture for the sustain-rail bloom effect.
-    // Returns a W×1 RGBA texture where alpha follows exp(-0.5*(u−0.5)²/σ²),
-    // peaking at 1.0 in the centre. With the default σ=0.28 the edges retain
-    // ~0.20 alpha (not fully transparent) — a deliberately soft, wide falloff
-    // so the additive bloom fades gradually rather than cutting off sharply.
-    // Power-of-two width keeps WebGL mipmapping happy.
-    function _makeGaussTex(ThreeLib, w = 128, sigma = 0.28) {
-        const data = new Uint8Array(w * 4);
-        for (let i = 0; i < w; i++) {
-            const u = i / (w - 1);
-            const d = (u - 0.5) / sigma;
-            const v = Math.exp(-0.5 * d * d);
-            const a = Math.round(v * 255);
-            data[i * 4]     = 255;
-            data[i * 4 + 1] = 255;
-            data[i * 4 + 2] = 255;
-            data[i * 4 + 3] = a;
-        }
-        const tex = new ThreeLib.DataTexture(data, w, 1, ThreeLib.RGBAFormat);
-        // LinearFilter on both axes so the bloom plane interpolates smoothly
-        // when scaled — the default NearestFilter causes visible banding.
-        tex.magFilter = ThreeLib.LinearFilter;
-        tex.minFilter = ThreeLib.LinearFilter;
-        tex.needsUpdate = true;
-        return tex;
-    }
 
     /* ======================================================================
      *  Three.js module — lazily loaded, memoized

plugins/highway_3d/src/geometry.js

@@ -0,0 +1,137 @@
+/**
+ * Pure geometry helpers — h3d-carve-1.
+ *
+ * All exports are stateless; they depend only on the compile-time constants
+ * below (which mirror their factory-scope counterparts in screen.js verbatim
+ * and never vary at runtime).  No DOM, no Three.js imports, no side-effects.
+ *
+ * screen.js keeps a 1-arg delegator:
+ *   const fretX = f => geoFretX(f, _h3dFretUniform);
+ * so no call site in screen.js changes.
+ */
+
+// ── Compile-time constants (mirror screen.js; never vary at runtime) ─────────
+
+const SCALE = 2.25;
+const K = SCALE / 300;
+// Horizontal stretch factor for fret X positions.
+const FRET_SCALE = SCALE * 1.1;
+const NFRETS = 24;
+/**
+ * Pure 12-semitone spacing compresses toward the bridge; multiply each
+ * segment above this fret by the factor so high positions stay
+ * slightly more playable/readable in 3D.
+ */
+const FRET_SPACING_STRETCH_ABOVE12 = 1.1;
+const FRET_SPACING_ANCHOR_F = 12;
+/** Note travel speed. */
+const TS = 230 * K;
+
+// ── Fret X ───────────────────────────────────────────────────────────────────
+
+// Logarithmic spacing — mirrors real guitar fret geometry (12th root of 2).
+const _fretXLog = f => {
+    if (f <= 0) return 0;
+    const raw = FRET_SCALE - FRET_SCALE / Math.pow(2, f / 12);
+    if (f <= FRET_SPACING_ANCHOR_F) return raw;
+    const rawAnchor = FRET_SCALE - FRET_SCALE / Math.pow(2, FRET_SPACING_ANCHOR_F / 12);
+    return rawAnchor + (raw - rawAnchor) * FRET_SPACING_STRETCH_ABOVE12;
+};
+// Uniform spacing — same column width per fret (chart-format style).
+// Total board width equals the logarithmic NFRETS position for consistency.
+const _fretXUniStep = _fretXLog(NFRETS) / NFRETS;
+const _fretXUni = f => f <= 0 ? 0 : f * _fretXUniStep;
+
+/**
+ * World-space X position for fret `f`.
+ * @param {number}  f       fret number
+ * @param {boolean} uniform true → uniform (chart-format) spacing; false → logarithmic
+ */
+export const geoFretX = (f, uniform) => uniform ? _fretXUni(f) : _fretXLog(f);
+
+// ── Time → Z ─────────────────────────────────────────────────────────────────
+
+/** Convert a time delta (seconds) to a world-space Z offset (notes travel toward −Z). */
+export const dZ = dt => -dt * TS;
+
+// ── Slide trail ───────────────────────────────────────────────────────────────
+
+/**
+ * Pitched slide uses `sl`, unpitched uses `slu` (slide-to vs unpitched slide fields).
+ * Prefer `sl` when both are present — matches RS wire.
+ * @returns {{ endFret: number, unpitched: boolean } | null}
+ */
+export function slideTrailEnd(n) {
+    const sl = n.sl;
+    const slu = n.slu;
+    if (Number.isFinite(sl) && sl >= 0) {
+        return { endFret: sl | 0, unpitched: false };
+    }
+    if (Number.isFinite(slu) && slu >= 0) {
+        return { endFret: slu | 0, unpitched: true };
+    }
+    return null;
+}
+
+// ── Camera distance building blocks ──────────────────────────────────────────
+
+// Camera tgtDist building blocks. Both the dynamic (camera-follow)
+// and locked (frets 1-12) branches compose tgtDist from these, so
+// any future tuning of the base zoom curve or low-fret pullback
+// lands in both branches without drift.
+//   span    — camDistMax - camDistMin in fret-span units
+//   minFret — lowest fretted note in the camera window (or 1 for
+//             the locked branch, which assumes nut chords)
+export const camBaseDistU = span => 65 + Math.max(span, 4) * 3;
+export const camLowFretPullbackU = minFret => Math.max(0, 5 - minFret) * 4;
+
+// ── BPM estimation ────────────────────────────────────────────────────────────
+
+export function computeBPM(beats, t) {
+    if (!beats || beats.length < 2) return 120;
+    let lo = 0, hi = beats.length;
+    while (lo < hi) {
+        const mid = (lo + hi) >> 1;
+        if (beats[mid].time < t) lo = mid + 1; else hi = mid;
+    }
+    let closest = lo;
+    if (lo === beats.length) closest = beats.length - 1;
+    else if (lo > 0 && Math.abs(beats[lo - 1].time - t) < Math.abs(beats[lo].time - t)) closest = lo - 1;
+    const start = Math.max(0, closest - 2);
+    const end = Math.min(beats.length - 1, closest + 2);
+    let sum = 0, count = 0;
+    for (let i = start; i < end; i++) {
+        const dt = beats[i + 1].time - beats[i].time;
+        if (dt > 0) { sum += dt; count++; }
+    }
+    return count > 0 && sum > 0 ? 60 / (sum / count) : 120;
+}
+
+// ── Gaussian bloom texture ────────────────────────────────────────────────────
+
+// Build a horizontal gaussian DataTexture for the sustain-rail bloom effect.
+// Returns a W×1 RGBA texture where alpha follows exp(-0.5*(u−0.5)²/σ²),
+// peaking at 1.0 in the centre. With the default σ=0.28 the edges retain
+// ~0.20 alpha (not fully transparent) — a deliberately soft, wide falloff
+// so the additive bloom fades gradually rather than cutting off sharply.
+// Power-of-two width keeps WebGL mipmapping happy.
+export function _makeGaussTex(ThreeLib, w = 128, sigma = 0.28) {
+    const data = new Uint8Array(w * 4);
+    for (let i = 0; i < w; i++) {
+        const u = i / (w - 1);
+        const d = (u - 0.5) / sigma;
+        const v = Math.exp(-0.5 * d * d);
+        const a = Math.round(v * 255);
+        data[i * 4]     = 255;
+        data[i * 4 + 1] = 255;
+        data[i * 4 + 2] = 255;
+        data[i * 4 + 3] = a;
+    }
+    const tex = new ThreeLib.DataTexture(data, w, 1, ThreeLib.RGBAFormat);
+    // LinearFilter on both axes so the bloom plane interpolates smoothly
+    // when scaled — the default NearestFilter causes visible banding.
+    tex.magFilter = ThreeLib.LinearFilter;
+    tex.minFilter = ThreeLib.LinearFilter;
+    tex.needsUpdate = true;
+    return tex;
+}

tests/js/highway_3d_fret_spacing.test.js

@@ -2,8 +2,12 @@
 // The board can render fret columns either Uniform (equal width, the chart
 // Remastered style) or Logarithmic (real instrument geometry), switchable at
 // runtime via window.h3dSetFretSpacing and persisted in localStorage. A
-// refactor that renames the storage key, drops the uniform/log branch in
+// refactor that renames the storage key, drops the delegator in fretX, or
-// fretX, or stops validating the mode would silently regress the setting.
+// stops validating the mode would silently regress the setting.
+//
+// Since h3d-carve-1, the uniform/log branch lives in src/geometry.js
+// (geoFretX); screen.js keeps a 1-arg delegator:
+//   const fretX = f => geoFretX(f, _h3dFretUniform);
 //
 // Source-level only — same strategy as the other tests/js/ files.
 
@@ -13,6 +17,7 @@ const fs = require('node:fs');
 const path = require('node:path');
 
 const SCREEN_JS = path.join(__dirname, '..', '..', 'plugins', 'highway_3d', 'screen.js');
+const GEOMETRY_JS = path.join(__dirname, '..', '..', 'plugins', 'highway_3d', 'src', 'geometry.js');
 
 test('fret-spacing mode is read from the highway_3d.fretSpacing localStorage key', () => {
     const src = fs.readFileSync(SCREEN_JS, 'utf8');
@@ -23,12 +28,18 @@ test('fret-spacing mode is read from the highway_3d.fretSpacing localStorage key
     );
 });
 
-test('fretX switches between the uniform and logarithmic implementations', () => {
+test('fretX is a 1-arg delegator to geoFretX in screen.js (h3d-carve-1)', () => {
     const src = fs.readFileSync(SCREEN_JS, 'utf8');
     assert.match(
         src,
-        /const\s+fretX\s*=\s*f\s*=>\s*_h3dFretUniform\s*\?\s*_fretXUni\(f\)\s*:\s*_fretXLog\(f\)/,
+        /const\s+fretX\s*=\s*f\s*=>\s*geoFretX\(\s*f\s*,\s*_h3dFretUniform\s*\)/,
-        'fretX must pick _fretXUni when _h3dFretUniform else _fretXLog',
+        'screen.js fretX must delegate to geoFretX(f, _h3dFretUniform) from geometry.js',
+    );
+    const geo = fs.readFileSync(GEOMETRY_JS, 'utf8');
+    assert.match(
+        geo,
+        /export\s+const\s+geoFretX\s*=\s*\(\s*f\s*,\s*uniform\s*\)\s*=>/,
+        'geometry.js must export geoFretX as a 2-arg function (fret, uniform)',
     );
 });
 

tests/js/highway_3d_geometry.test.js

@@ -0,0 +1,80 @@
+// Class-killer for src/geometry.js — h3d-carve-1.
+//
+// Uses dynamic import() (not the vm source-scan pattern) so Node actually
+// evaluates the ES module and its exports are the real runtime values.
+// A refactor that renames geoFretX, changes the uniform/logarithmic
+// decision, removes slideTrailEnd, or breaks computeBPM's BPM estimate
+// would be caught here before any other test.
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const path = require('node:path');
+
+const GEOMETRY_JS = path.join(__dirname, '..', '..', 'plugins', 'highway_3d', 'src', 'geometry.js');
+
+test('geoFretX returns 0 for fret 0 in both modes', async () => {
+    const { geoFretX } = await import(GEOMETRY_JS);
+    assert.strictEqual(geoFretX(0, true),  0, 'uniform: fret 0 must be 0');
+    assert.strictEqual(geoFretX(0, false), 0, 'logarithmic: fret 0 must be 0');
+});
+
+test('geoFretX uniform spacing is linear — fret N is N × fret 1', async () => {
+    const { geoFretX } = await import(GEOMETRY_JS);
+    const step = geoFretX(1, true);
+    assert.ok(step > 0, 'uniform step must be positive');
+    assert.ok(Math.abs(geoFretX(5, true) - 5 * step) < 1e-9, 'fret 5 must be 5 × step');
+    assert.ok(Math.abs(geoFretX(12, true) - 12 * step) < 1e-9, 'fret 12 must be 12 × step');
+});
+
+test('geoFretX logarithmic spacing is non-linear — frets compress toward the bridge', async () => {
+    const { geoFretX } = await import(GEOMETRY_JS);
+    const d1 = geoFretX(1, false);
+    const d2 = geoFretX(2, false) - geoFretX(1, false);
+    const d3 = geoFretX(3, false) - geoFretX(2, false);
+    assert.ok(d1 > d2, 'fret 1 gap must be wider than fret 2 gap (compression toward bridge)');
+    assert.ok(d2 > d3, 'fret 2 gap must be wider than fret 3 gap');
+});
+
+test('geoFretX uniform and logarithmic agree at fret 24 (total board width)', async () => {
+    const { geoFretX } = await import(GEOMETRY_JS);
+    // By construction: _fretXUniStep = _fretXLog(24) / 24, so geoFretX(24, uniform)
+    // equals geoFretX(24, logarithmic). This is the board-width invariant.
+    const uniWidth = geoFretX(24, true);
+    const logWidth = geoFretX(24, false);
+    assert.ok(Math.abs(uniWidth - logWidth) < 1e-9, 'board width must be identical in both modes');
+});
+
+test('dZ converts positive dt to a negative Z delta', async () => {
+    const { dZ } = await import(GEOMETRY_JS);
+    assert.ok(dZ(1) < 0, 'positive time delta must produce negative Z (notes travel toward camera)');
+    assert.ok(dZ(0) === 0, 'zero dt must produce zero dZ');
+    assert.ok(Math.abs(dZ(2) / dZ(1) - 2) < 1e-9, 'dZ must be linear in dt');
+});
+
+test('slideTrailEnd returns null for notes with no slide fields', async () => {
+    const { slideTrailEnd } = await import(GEOMETRY_JS);
+    assert.strictEqual(slideTrailEnd({}), null);
+    assert.strictEqual(slideTrailEnd({ sl: -1 }), null, 'negative sl must be ignored');
+});
+
+test('slideTrailEnd prefers sl over slu and marks pitched/unpitched correctly', async () => {
+    const { slideTrailEnd } = await import(GEOMETRY_JS);
+    assert.deepStrictEqual(slideTrailEnd({ sl: 7 }),         { endFret: 7, unpitched: false });
+    assert.deepStrictEqual(slideTrailEnd({ slu: 5 }),        { endFret: 5, unpitched: true });
+    assert.deepStrictEqual(slideTrailEnd({ sl: 7, slu: 5 }), { endFret: 7, unpitched: false });
+});
+
+test('computeBPM returns 120 for degenerate inputs', async () => {
+    const { computeBPM } = await import(GEOMETRY_JS);
+    assert.strictEqual(computeBPM(null, 0), 120);
+    assert.strictEqual(computeBPM([], 0),   120);
+    assert.strictEqual(computeBPM([{ time: 0 }], 0), 120, 'single beat has no interval');
+});
+
+test('computeBPM estimates 120 BPM from evenly-spaced beats', async () => {
+    const { computeBPM } = await import(GEOMETRY_JS);
+    // 120 BPM = 0.5 s per beat
+    const beats = [0, 0.5, 1.0, 1.5, 2.0].map(time => ({ time }));
+    const bpm = computeBPM(beats, 1.0);
+    assert.ok(Math.abs(bpm - 120) < 0.01, `expected ~120 BPM, got ${bpm}`);
+});

tests/js/highway_3d_panel_controls.test.js

@@ -28,7 +28,11 @@ function loadHighway3dStatics() {
         1,
         'expected exactly one factory-registration anchor in screen.js',
     );
-    const instrumented = src.replace(
+    // Since h3d-carve-1 screen.js starts with an ES module import statement.
+    // vm.runInContext does not support static import — strip the import line
+    // and provide stub implementations of the geometry exports in the sandbox.
+    const stripped = src.replace(/^import\s+\{[^}]+\}\s+from\s+['"][^'"]+['"];\s*\/\/[^\n]*\n/m, '');
+    const instrumented = stripped.replace(
         ANCHOR,
         `${ANCHOR}\n    window.__h3dTestExports = { BG_DEFAULTS };`,
     );
@@ -50,6 +54,15 @@ function loadHighway3dStatics() {
                 register() {},
             },
         },
+        // Geometry stubs — panel-controls test only reads factory statics;
+        // it never invokes the render path where these are called (h3d-carve-1).
+        geoFretX: (f, _uniform) => f * 0.1,
+        dZ: dt => -dt,
+        slideTrailEnd: () => null,
+        camBaseDistU: span => span,
+        camLowFretPullbackU: () => 0,
+        computeBPM: () => 120,
+        _makeGaussTex: () => ({}),
     };
     vm.createContext(sandbox);
     vm.runInContext(instrumented, sandbox, { filename: SCREEN_JS });

tests/js/highway_3d_sustain_bloom.test.js

@@ -5,6 +5,10 @@
 // stops using additive blending, or bumps the bloom renderOrder above the
 // core rail (16) would silently regress or invert the effect.
 //
+// Since h3d-carve-1, _makeGaussTex is defined in src/geometry.js and
+// imported into screen.js; the call site (_bloomGaussTex = _makeGaussTex(...))
+// remains in screen.js.
+//
 // Source-level only — same strategy as the other tests/js/ files.
 
 const { test } = require('node:test');
@@ -13,14 +17,16 @@ const fs = require('node:fs');
 const path = require('node:path');
 
 const SCREEN_JS = path.join(__dirname, '..', '..', 'plugins', 'highway_3d', 'screen.js');
+const GEOMETRY_JS = path.join(__dirname, '..', '..', 'plugins', 'highway_3d', 'src', 'geometry.js');
 
 test('a gaussian DataTexture helper (_makeGaussTex) drives the bloom falloff', () => {
-    const src = fs.readFileSync(SCREEN_JS, 'utf8');
+    const geo = fs.readFileSync(GEOMETRY_JS, 'utf8');
     assert.match(
-        src,
+        geo,
-        /function\s+_makeGaussTex\s*\(/,
+        /export\s+function\s+_makeGaussTex\s*\(/,
-        '_makeGaussTex must exist to build the bloom gaussian texture',
+        '_makeGaussTex must be exported from geometry.js to build the bloom gaussian texture',
     );
+    const src = fs.readFileSync(SCREEN_JS, 'utf8');
     assert.match(
         src,
         /_bloomGaussTex\s*=\s*_makeGaussTex\(/,