diff --git a/web/src/cases/algs.test.ts b/web/src/cases/algs.test.ts
index b695d98..7e17aae 100644
--- a/web/src/cases/algs.test.ts
+++ b/web/src/cases/algs.test.ts
@@ -6,6 +6,7 @@ import { stageLevel } from '../solve/cfop'
 import { algsFor, ALT_ALGS, defaultAlg, usesF } from './algs'
 import { ALL_CASES } from './data'
 import { applyNormalized, caseSignature, ROTATIONS } from './geometry'
+import { caseForAlg } from './seed'
 
 const kpuzzle = await cube3x3x3.kpuzzle()
 
@@ -34,6 +35,29 @@ describe('alternative algs', () => {
   })
 })
 
+describe('diagram follows the chosen alg', () => {
+  const c = (id: string) => ALL_CASES.find((x) => x.id === id)!
+  // 面の上段の両端のシール（R：9・11、F：18・20）が同じ色ならヘッドライト
+  const headlights = (f: string, a: number, b: number) => f[a] === f[b]
+
+  it("draws Aa's headlights on the right for x' R2 D2 R' U' R D2 R' U R' x", () => {
+    const alg = "x' R2 D2 R' U' R D2 R' U R' x"
+    expect(algsFor(c('pll-Aa'))).toContain(alg)
+    expect(headlights(caseForAlg(kpuzzle, { alg: c('pll-Aa').alg, pattern: '' }, alg).pattern, 9, 11)).toBe(true)
+  })
+
+  it("draws Ab's headlights in front for R B' R F2 R' B R F2 R2", () => {
+    const alg = "R B' R F2 R' B R F2 R2"
+    expect(algsFor(c('pll-Ab'))).toContain(alg)
+    expect(headlights(caseForAlg(kpuzzle, { alg: c('pll-Ab').alg, pattern: '' }, alg).pattern, 18, 20)).toBe(true)
+  })
+
+  it('keeps the stored pattern for the standard alg', () => {
+    const x = { alg: "R U R'", pattern: 'stored' }
+    expect(caseForAlg(kpuzzle, x, x.alg)).toBe(x)
+  })
+})
+
 describe('F2L without F', () => {
   const f2l = ALL_CASES.filter((c) => c.set === 'F2L')
 
diff --git a/web/src/cases/algs.ts b/web/src/cases/algs.ts
index bde1ccb..299c5df 100644
--- a/web/src/cases/algs.ts
+++ b/web/src/cases/algs.ts
@@ -29,7 +29,7 @@ export const ALT_ALGS: Record<string, string[]> = {
   'oll-51': ["f R U R' U' R U R' U' f'"],
   'oll-52': ["R' F' U' F U' R U R' U R"],
   'oll-57': ["R U R' U' r R' U R U' r'"],
-  'pll-Aa': ["x L2 D2 L' U' L D2 L' U L' x'", "R' F R' B2 R F' R' B2 R2"],
+  'pll-Aa': ["x L2 D2 L' U' L D2 L' U L' x'", "R' F R' B2 R F' R' B2 R2", "x' R2 D2 R' U' R D2 R' U R' x"],
   'pll-Ab': ["x' L2 D2 L U L' D2 L U' L x", "R B' R F2 R' B R F2 R2"],
   'pll-H': ["M2 U' M2 U2 M2 U' M2", 'R2 U2 R U2 R2 U2 R2 U2 R U2 R2'],
   'pll-Ua': ["R U' R U R U R U' R' U' R2", "R2 U' R' U' R U R U R U' R"],
diff --git a/web/src/cases/seed.ts b/web/src/cases/seed.ts
index ad5882d..78b5eff 100644
--- a/web/src/cases/seed.ts
+++ b/web/src/cases/seed.ts
@@ -11,6 +11,19 @@ export function casePattern(kpuzzle: KPuzzle, alg: string): string {
   return patternToFacelets(applyNormalized(kpuzzle, new Alg(alg).invert().toString()))
 }
 
+const patterns = new Map<string, string>()
+
+/** ケースの図を、その手順で揃う向きにしたもの（別手順はヘッドライトなどの向きが標準手順と違うことがある）。 */
+export function caseForAlg<T extends { alg: string; pattern: string }>(kpuzzle: KPuzzle, c: T, alg: string): T {
+  if (!alg || alg === c.alg) return c
+  let pattern = patterns.get(alg)
+  if (pattern === undefined) {
+    pattern = casePattern(kpuzzle, alg)
+    patterns.set(alg, pattern)
+  }
+  return { ...c, pattern }
+}
+
 const q = (s: string) => `'${s.replace(/'/g, "''")}'`
 
 export function casesMigrationSQL(kpuzzle: KPuzzle): string {
diff --git a/web/src/pages/AlgDrillPage.tsx b/web/src/pages/AlgDrillPage.tsx
index 29a575b..df876c7 100644
--- a/web/src/pages/AlgDrillPage.tsx
+++ b/web/src/pages/AlgDrillPage.tsx
@@ -6,6 +6,7 @@ import { useAlgDrill, useCaseSetup, useCaseSetupState, useDrillState } from '../
 import type { CaseSetup, CaseSetupState } from '../cases/setup'
 import { scrambleBetween } from '../cases/exercise'
 import { invertRotation, normalizeOrientation } from '../cases/geometry'
+import { caseForAlg } from '../cases/seed'
 import { caseStats } from '../cases/stats'
 import { CaseDiagram } from '../components/CaseDiagram'
 import { FitLayout } from '../components/FitLayout'
@@ -56,6 +57,7 @@ export function AlgDrillPage({ initialCaseId }: { initialCaseId?: string | null
   const [selectedId, setSelectedId] = useState<string | null>(() => (setOf(initialCaseId) ? initialCaseId! : null))
   const [running, setRunning] = useState(false)
   const [chosenAlg, setChosenAlg] = useState<Record<string, string>>({})
+  const store = useCubeStore()
   const history = useSolveList({ mode: 'case', limit: 0 })
   const stats = useMemo(() => caseStats(history.solves), [history.solves])
 
@@ -74,7 +76,8 @@ export function AlgDrillPage({ initialCaseId }: { initialCaseId?: string | null
       setError(`「覚えた」を保存できませんでした: ${String(err)}`)
     })
   }
-  const alg = selected ? (chosenAlg[selected.id] ?? preferredAlg(selected)) : ''
+  const algOf = (c: CaseInfo) => chosenAlg[c.id] ?? preferredAlg(c)
+  const alg = selected ? algOf(selected) : ''
   const chooseAlg = (id: string, a: string) => {
     setChosenAlg((prev) => ({ ...prev, [id]: a }))
     savePreferredAlg(id, a)
@@ -106,7 +109,7 @@ export function AlgDrillPage({ initialCaseId }: { initialCaseId?: string | null
       {selected && (
         <section className="panel drill-selected" aria-live="polite">
           <div className="row">
-            <CaseDiagram c={selected} size={96} arrows />
+            <CaseDiagram c={caseForAlg(store.kpuzzle, selected, alg)} size={96} arrows />
             <div className="drill-selected-info">
               <div className="row">
                 <strong>{selected.name}</strong>
@@ -165,7 +168,7 @@ export function AlgDrillPage({ initialCaseId }: { initialCaseId?: string | null
                     onClick={() => setSelectedId(c.id)}
                     title={c.alg}
                   >
-                    <CaseDiagram c={c} />
+                    <CaseDiagram c={caseForAlg(store.kpuzzle, c, algOf(c))} />
                     <div className="case-name">
                       {c.learned && <span className="learned-mark" aria-label="覚えた">✓</span>}
                       {c.name}
@@ -296,7 +299,7 @@ function DrillView({ c, alg, onBack, onSaved }: { c: CaseInfo; alg: string; onBa
           </div>
 
           <section className="panel drill-head">
-            <CaseDiagram c={c} size={88} arrows />
+            <CaseDiagram c={caseForAlg(store.kpuzzle, c, alg)} size={88} arrows />
             <div>
               <strong>{c.name}</strong>
               <div className="alg drill-alg">{alg}</div>
diff --git a/web/src/pages/AssistPractice.tsx b/web/src/pages/AssistPractice.tsx
index a4dcef1..978a008 100644
--- a/web/src/pages/AssistPractice.tsx
+++ b/web/src/pages/AssistPractice.tsx
@@ -5,6 +5,7 @@ import { listCases, type CaseInfo, type NewSolve, type Solve } from '../api'
 import { stickyAssist, viewFrom, type Assist, type StickyAssist } from '../assist/detect'
 import { preferredAlg } from '../cases/algs'
 import type { CaseDef } from '../cases/data'
+import { caseForAlg } from '../cases/seed'
 import { CaseDiagram } from '../components/CaseDiagram'
 import { PracticeRunner } from '../components/PracticeRunner'
 import { useCubeStore } from '../cube/hooks'
@@ -253,6 +254,7 @@ function CaseHint({
   show: boolean
   missing?: string
 }) {
+  const store = useCubeStore()
   return (
     <div className="assist-case row">
       {place && <span className="assist-slot">{place}</span>}
@@ -262,7 +264,7 @@ function CaseHint({
         <span className="muted">考え中…</span>
       ) : (
         <>
-          {info && <CaseDiagram c={info} size={56} arrows />}
+          {info && <CaseDiagram c={caseForAlg(store.kpuzzle, info, preferredAlg(info))} size={56} arrows />}
           <div>
             <div>
               <strong>{c.name}</strong>