Implement FSRS-4.5 17-parameter DSR spaced repetition scheduler with algorithm toggle and live metrics

www/rhetorik_trainer_quiz.html

@@ -240,24 +240,42 @@
     <!-- VIEW 1: FLASHCARDS (Leitner 5-Box-System)  -->
     <!-- ========================================== -->
     <section id="view-cards" class="space-y-4 sm:space-y-5">
-      <!-- Filter Bar: Categories & Leitner Boxes -->
+      <!-- Filter Bar: Categories & Algorithm Selectors -->
       <div class="bg-white p-4 sm:p-5 rounded-2xl border border-slate-200/80 shadow-sm space-y-3.5">
         <div class="flex flex-col lg:flex-row justify-between items-start lg:items-center gap-3 sm:gap-4">
           <div>
-            <h2 class="text-base sm:text-xl font-extrabold text-slate-900 flex items-center gap-2">
-              <span>Leitner-Karteikarten (5-Kasten-System)</span>
-            </h2>
-            <p class="text-xs sm:text-sm text-slate-500 mt-0.5">Wische nach links (wiederholen) oder rechts (gekonnt) oder tippe zum Wenden.</p>
+            <div class="flex items-center gap-2.5 flex-wrap">
+              <h2 id="cardSectionTitle" class="text-base sm:text-xl font-extrabold text-slate-900 flex items-center gap-2">
+                <i class="fa-solid fa-brain text-indigo-600"></i>
+                <span>FSRS-4.5 Karteikasten</span>
+              </h2>
+              <span id="algoHeaderBadge" class="px-2.5 py-0.5 rounded-full bg-indigo-50 border border-indigo-200 text-indigo-700 font-extrabold text-[11px] uppercase tracking-wider">Spaced Repetition</span>
+            </div>
+            <p id="cardSectionSubtitle" class="text-xs sm:text-sm text-slate-500 mt-1">
+              Modernes 17-Parameter DSR-Modell (Retrievability, Stability, Difficulty) – 20–30 % weniger Wiederholungen bei 90 % Behaltungsquote.
+            </p>
           </div>
 
           <div class="flex flex-wrap items-center gap-2 w-full lg:w-auto justify-between lg:justify-end">
+            <!-- Algorithm Toggle -->
+            <div class="inline-flex p-1 bg-slate-100 rounded-xl border border-slate-200 text-xs sm:text-sm font-bold shadow-inner">
+              <button id="algoFsrsBtn" onclick="setSpacedRepetitionAlgo('fsrs')" class="px-2.5 sm:px-3 py-1.5 rounded-lg bg-white text-indigo-700 shadow-sm transition font-bold flex items-center gap-1.5">
+                <i class="fa-solid fa-bolt text-indigo-500"></i>
+                <span>FSRS (KI)</span>
+              </button>
+              <button id="algoLeitnerBtn" onclick="setSpacedRepetitionAlgo('leitner')" class="px-2.5 sm:px-3 py-1.5 rounded-lg text-slate-600 hover:text-slate-900 transition font-semibold flex items-center gap-1.5">
+                <i class="fa-solid fa-boxes-stacked"></i>
+                <span>5-Kasten</span>
+              </button>
+            </div>
+
             <!-- Card Face Toggle -->
             <div class="inline-flex p-1 bg-slate-100 rounded-xl border border-slate-200 text-xs sm:text-sm font-bold">
               <button id="cardModeTermBtn" onclick="setCardFaceMode('term')" class="px-3 py-1.5 rounded-lg bg-white text-indigo-700 shadow-sm transition font-bold">
-                Begriff zuerst
+                Begriff
               </button>
               <button id="cardModeExampleBtn" onclick="setCardFaceMode('example')" class="px-3 py-1.5 rounded-lg text-slate-600 hover:text-slate-900 transition font-semibold">
-                Beispiel zuerst
+                Beispiel
               </button>
             </div>
 
@@ -266,7 +284,7 @@
               <button onclick="shuffleCards()" title="Karten mischen" class="p-2 sm:px-3 sm:py-2 rounded-xl border border-slate-200 hover:bg-slate-100 text-slate-600 text-xs sm:text-sm font-bold transition flex items-center gap-1">
                 <i class="fa-solid fa-shuffle"></i>
               </button>
-              <button onclick="resetLeitnerProgress()" title="Lernstand für Karten zurücksetzen" class="p-2 sm:px-3 sm:py-2 rounded-xl border border-slate-200 hover:bg-rose-50 hover:text-rose-600 text-slate-500 text-xs sm:text-sm font-bold transition flex items-center gap-1">
+              <button onclick="resetCardProgressPrompt()" title="Lernstand für Karten zurücksetzen" class="p-2 sm:px-3 sm:py-2 rounded-xl border border-slate-200 hover:bg-rose-50 hover:text-rose-600 text-slate-500 text-xs sm:text-sm font-bold transition flex items-center gap-1">
                 <i class="fa-solid fa-rotate-left"></i>
               </button>
             </div>
@@ -288,8 +306,8 @@
             <button onclick="setCardCategoryFilter('gedanke')" id="cardCatBtn-gedanke" class="card-cat-pill px-3 py-1.5 rounded-xl font-semibold bg-slate-100 text-slate-600 hover:bg-slate-200">Gedanken</button>
           </div>
 
-          <!-- Leitner Box Filter -->
-          <div class="flex items-center gap-1.5">
+          <!-- Leitner Box Filter (Active in Leitner Mode) -->
+          <div id="leitnerFilterWrap" class="flex items-center gap-1.5 hidden">
             <span class="font-bold text-slate-400 uppercase text-[11px] mr-1">Kasten:</span>
             <select id="leitnerBoxFilter" onchange="filterByLeitnerBox(this.value)" class="bg-slate-100 border border-slate-200 text-slate-700 text-xs sm:text-sm rounded-xl px-3 py-1.5 font-bold focus:outline-none focus:ring-1 focus:ring-indigo-500">
               <option value="all">Alle Kästen (1-5)</option>
@@ -300,14 +318,27 @@
               <option value="5">Kasten 5 (Gemeistert)</option>
             </select>
           </div>
+
+          <!-- FSRS Queue Filter (Active in FSRS Mode) -->
+          <div id="fsrsFilterWrap" class="flex items-center gap-1.5">
+            <span class="font-bold text-slate-400 uppercase text-[11px] mr-1">Intervall:</span>
+            <select id="fsrsQueueFilter" onchange="filterByFsrsQueue(this.value)" class="bg-indigo-50/70 border border-indigo-200 text-indigo-900 text-xs sm:text-sm rounded-xl px-3 py-1.5 font-extrabold focus:outline-none focus:ring-1 focus:ring-indigo-500">
+              <option value="all">Alle Karten</option>
+              <option value="due" selected>📅 Jetzt fällig</option>
+              <option value="learning">📈 In Wiederholung</option>
+              <option value="new">🌱 Noch unberührt</option>
+            </select>
+          </div>
         </div>
       </div>
 
-      <!-- Progress bar & Leitner Box Indicators -->
+      <!-- Progress bar & Algorithm Indicators -->
       <div class="space-y-1.5">
-        <div class="flex justify-between items-center text-xs sm:text-sm text-slate-600 font-bold px-1">
+        <div class="flex flex-wrap justify-between items-center text-xs sm:text-sm text-slate-600 font-bold px-1 gap-2">
           <span id="cardProgressLabel">Karte 1 von 17 (🌟 Kernstoff)</span>
-          <div class="flex items-center gap-2">
+
+          <!-- Leitner Box Visual Indicators -->
+          <div id="leitnerMetricsContainer" class="flex items-center gap-2 hidden">
             <span id="cardBoxBadge" class="px-2.5 py-0.5 rounded-lg bg-amber-50 text-amber-800 border border-amber-200 font-bold text-xs">Kasten 1</span>
             <div id="leitnerBoxesVisual" class="flex gap-1">
               <span class="w-2.5 h-2.5 rounded-full bg-indigo-600"></span>
@@ -317,6 +348,26 @@
               <span class="w-2.5 h-2.5 rounded-full bg-slate-200"></span>
             </div>
           </div>
+
+          <!-- FSRS DSR Live Metrics -->
+          <div id="fsrsMetricsContainer" class="flex flex-wrap items-center gap-1.5 text-[11px] sm:text-xs">
+            <span id="fsrsDueBadge" class="px-2.5 py-0.5 rounded-lg bg-rose-50 text-rose-700 border border-rose-200 font-extrabold flex items-center gap-1">
+              <i class="fa-solid fa-clock"></i>
+              <span>Fällig</span>
+            </span>
+            <span id="fsrsRetrievabilityBadge" title="Retrievability: Geschätzte Abrufwahrscheinlichkeit" class="px-2.5 py-0.5 rounded-lg bg-emerald-50 text-emerald-800 border border-emerald-200 font-extrabold flex items-center gap-1">
+              <i class="fa-solid fa-gauge-high text-emerald-600"></i>
+              <span>R: 90%</span>
+            </span>
+            <span id="fsrsStabilityBadge" title="Stability: Gedächtnisstabilität in Tagen (Intervall bis R=90%)" class="px-2.5 py-0.5 rounded-lg bg-blue-50 text-blue-800 border border-blue-200 font-bold flex items-center gap-1">
+              <i class="fa-solid fa-calendar-day text-blue-500"></i>
+              <span>S: 3.1 T</span>
+            </span>
+            <span id="fsrsDifficultyBadge" title="Difficulty: Berechnete Kartenschwierigkeit von 1 bis 10" class="px-2.5 py-0.5 rounded-lg bg-amber-50 text-amber-800 border border-amber-200 font-bold flex items-center gap-1">
+              <i class="fa-solid fa-weight-scale text-amber-500"></i>
+              <span>D: 5.3</span>
+            </span>
+          </div>
         </div>
         <div class="w-full bg-slate-200 h-2.5 rounded-full overflow-hidden">
           <div id="cardProgressBar" class="bg-indigo-600 h-full transition-all duration-300 w-0"></div>
@@ -410,13 +461,15 @@
         </div>
 
         <!-- Action Buttons -->
-        <div class="flex items-center justify-between gap-2.5 sm:gap-4 mt-6">
-          <button onclick="prevCard()" class="px-4 py-3 sm:py-3.5 rounded-2xl bg-white border border-slate-200 hover:bg-slate-50 text-slate-700 font-bold text-sm sm:text-base shadow-sm transition flex items-center gap-1.5">
+        <!-- Action Buttons -->
+        <div class="flex items-center justify-between gap-2 sm:gap-4 mt-6">
+          <button onclick="prevCard()" class="px-3.5 sm:px-4 py-3 sm:py-3.5 rounded-2xl bg-white border border-slate-200 hover:bg-slate-50 text-slate-700 font-bold text-sm sm:text-base shadow-sm transition flex items-center gap-1.5 flex-shrink-0">
             <i class="fa-solid fa-chevron-left"></i>
             <span class="hidden sm:inline">Zurück</span>
           </button>
 
-          <div class="flex items-center gap-2.5 sm:gap-3">
+          <!-- LEITNER ACTION BUTTONS (2 Options) -->
+          <div id="leitnerActionButtons" class="flex items-center gap-2.5 sm:gap-3 hidden">
             <button onclick="markCardMastered(false)" class="px-4 sm:px-6 py-3 sm:py-3.5 rounded-2xl bg-rose-50 hover:bg-rose-100 text-rose-700 border border-rose-200 font-extrabold text-sm sm:text-base transition flex items-center gap-2 shadow-sm">
               <span class="hidden md:inline-block px-1.5 py-0.5 bg-rose-200/80 rounded font-mono text-xs">1</span>
               <i class="fa-solid fa-rotate-left"></i>
@@ -429,7 +482,50 @@
             </button>
           </div>
 
-          <button onclick="nextCard()" class="px-4 py-3 sm:py-3.5 rounded-2xl bg-white border border-slate-200 hover:bg-slate-50 text-slate-700 font-bold text-sm sm:text-base shadow-sm transition flex items-center gap-1.5">
+          <!-- FSRS ACTION BUTTONS (4 Ratings with Predicted Next Interval Badges) -->
+          <div id="fsrsActionButtons" class="flex flex-wrap items-center justify-center gap-1.5 sm:gap-2.5">
+            <!-- 1: Nochmal / Again -->
+            <button onclick="rateFsrsCard(1)" class="px-2.5 sm:px-4 py-2 sm:py-2.5 rounded-2xl bg-rose-50 hover:bg-rose-100 text-rose-700 border border-rose-200 font-extrabold text-xs sm:text-sm transition flex flex-col items-center shadow-sm hover:scale-[1.02] active:scale-95">
+              <div class="flex items-center gap-1">
+                <span class="hidden md:inline-block px-1 py-0.2 bg-rose-200/80 rounded font-mono text-[10px]">1</span>
+                <i class="fa-solid fa-rotate-left"></i>
+                <span>Nochmal</span>
+              </div>
+              <span id="fsrsIntervalAgain" class="text-[10px] text-rose-600 font-semibold mt-0.5">&lt; 10 Min</span>
+            </button>
+
+            <!-- 2: Schwer / Hard -->
+            <button onclick="rateFsrsCard(2)" class="px-2.5 sm:px-4 py-2 sm:py-2.5 rounded-2xl bg-amber-50 hover:bg-amber-100 text-amber-800 border border-amber-200 font-extrabold text-xs sm:text-sm transition flex flex-col items-center shadow-sm hover:scale-[1.02] active:scale-95">
+              <div class="flex items-center gap-1">
+                <span class="hidden md:inline-block px-1 py-0.2 bg-amber-200/80 rounded font-mono text-[10px]">2</span>
+                <i class="fa-solid fa-triangle-exclamation"></i>
+                <span>Schwer</span>
+              </div>
+              <span id="fsrsIntervalHard" class="text-[10px] text-amber-700 font-semibold mt-0.5">+1 Tag</span>
+            </button>
+
+            <!-- 3: Gut / Good -->
+            <button onclick="rateFsrsCard(3)" class="px-2.5 sm:px-4 py-2 sm:py-2.5 rounded-2xl bg-emerald-50 hover:bg-emerald-100 text-emerald-800 border border-emerald-300 font-extrabold text-xs sm:text-sm transition flex flex-col items-center shadow-sm hover:scale-[1.02] active:scale-95">
+              <div class="flex items-center gap-1">
+                <span class="hidden md:inline-block px-1 py-0.2 bg-emerald-200/80 rounded font-mono text-[10px]">3</span>
+                <i class="fa-solid fa-check"></i>
+                <span>Gut</span>
+              </div>
+              <span id="fsrsIntervalGood" class="text-[10px] text-emerald-700 font-semibold mt-0.5">+3 Tage</span>
+            </button>
+
+            <!-- 4: Einfach / Easy -->
+            <button onclick="rateFsrsCard(4)" class="px-2.5 sm:px-4 py-2 sm:py-2.5 rounded-2xl bg-indigo-50 hover:bg-indigo-100 text-indigo-700 border border-indigo-200 font-extrabold text-xs sm:text-sm transition flex flex-col items-center shadow-sm hover:scale-[1.02] active:scale-95">
+              <div class="flex items-center gap-1">
+                <span class="hidden md:inline-block px-1 py-0.2 bg-indigo-200/80 rounded font-mono text-[10px]">4</span>
+                <i class="fa-solid fa-wand-magic-sparkles"></i>
+                <span>Einfach</span>
+              </div>
+              <span id="fsrsIntervalEasy" class="text-[10px] text-indigo-600 font-semibold mt-0.5">+15 Tage</span>
+            </button>
+          </div>
+
+          <button onclick="nextCard()" class="px-3.5 sm:px-4 py-3 sm:py-3.5 rounded-2xl bg-white border border-slate-200 hover:bg-slate-50 text-slate-700 font-bold text-sm sm:text-base shadow-sm transition flex items-center gap-1.5 flex-shrink-0">
             <span class="hidden sm:inline">Weiter</span>
             <i class="fa-solid fa-chevron-right"></i>
           </button>
@@ -1883,10 +1979,29 @@
       }
     }
 
-    // Leitner 5-Box State
+    // ==========================================
+    // FSRS-4.5 (FREE SPACED REPETITION SCHEDULER) ENGINE
+    // 17-Parameter DSR (Difficulty, Stability, Retrievability) Model
+    // ==========================================
+    const FSRS_WEIGHTS = [
+      0.4072, 1.1829, 3.1262, 15.4722, // w0-w3: Initial stability for ratings 1 (Again), 2 (Hard), 3 (Good), 4 (Easy)
+      7.2102, 0.5316,                  // w4, w5: Initial difficulty parameters
+      1.0651, 0.0234,                  // w6, w7: Next difficulty shift & mean reversion to D0(3)
+      1.616, 0.1544, 1.0824,           // w8, w9, w10: Stability after recall
+      1.9813, 0.0953, 0.2975, 0.472,   // w11, w12, w13, w14: Stability after forgetting
+      0.2655, 1.0                      // w15: Hard penalty factor, w16: Easy bonus factor
+    ];
+    const FSRS_FACTOR = 19 / 81; // ~0.2345679 (Power forgetting factor)
+    const FSRS_DESIRED_RETENTION = 0.90; // 90 % Behaltensquote
+
+    // Algorithm & Card States
+    let cardAlgo = localStorage.getItem('rhetorik_card_algo') || 'fsrs';
+    let fsrsCards = JSON.parse(localStorage.getItem('rhetorik_fsrs_cards') || '{}');
     let cardLevels = JSON.parse(localStorage.getItem('rhetorik_leitner_levels') || '{}');
+
     let activeCardCategory = 'highlighted';
     let activeLeitnerBox = 'all';
+    let activeFsrsQueue = 'all';
     let filteredCards = [...STILMITTEL_DATA];
 
     let currentTabIndex = 'cards';
@@ -1909,6 +2024,87 @@
     // Glossary State
     let currentGlossaryFilter = 'all';
 
+    // ==========================================
+    // FSRS MATH CALCULATIONS
+    // ==========================================
+    function getFsrsCard(id) {
+      return fsrsCards[id] || { s: 0, d: 0, reps: 0, lapses: 0, lastReview: 0, dueDate: 0, state: 0 };
+    }
+
+    function getElapsedDays(lastReview) {
+      if (!lastReview || lastReview <= 0) return 0;
+      return Math.max(0, (Date.now() - lastReview) / 86400000);
+    }
+
+    function calcRetrievability(tDays, s) {
+      if (!s || s <= 0) return 0;
+      return Math.pow(1 + FSRS_FACTOR * (tDays / s), -0.5);
+    }
+
+    function calcInitDifficulty(grade) {
+      const d = FSRS_WEIGHTS[4] - Math.exp(FSRS_WEIGHTS[5] * (grade - 1)) + 1;
+      return Math.min(10, Math.max(1, d));
+    }
+
+    function calcNextDifficulty(d, grade) {
+      const d0_3 = calcInitDifficulty(3);
+      const dPrime = d - FSRS_WEIGHTS[6] * (grade - 3);
+      const nextD = FSRS_WEIGHTS[7] * d0_3 + (1 - FSRS_WEIGHTS[7]) * dPrime;
+      return Math.min(10, Math.max(1, nextD));
+    }
+
+    function calcNextStability(cardData, grade, tDays) {
+      const w = FSRS_WEIGHTS;
+      if (!cardData || !cardData.reps || cardData.reps === 0) {
+        return Math.max(0.1, w[grade - 1]);
+      }
+      const r = Math.min(1, Math.max(0, calcRetrievability(tDays, cardData.s)));
+      const d = cardData.d || calcInitDifficulty(3);
+
+      if (grade === 1) {
+        const sForget = w[11] * Math.pow(d, -w[12]) * (Math.pow(cardData.s + 1, w[13]) - 1) * Math.exp((1 - r) * w[14]);
+        return Math.max(0.1, Math.min(cardData.s, sForget));
+      } else {
+        let h = 1;
+        if (grade === 2) h = w[15];
+        if (grade === 4) h = w[16];
+        const sRecall = cardData.s * (1 + Math.exp(w[8]) * (11 - d) * Math.pow(cardData.s, -w[9]) * (Math.exp((1 - r) * w[10]) - 1) * h);
+        return Math.max(0.1, sRecall);
+      }
+    }
+
+    function calcNextInterval(s, grade) {
+      if (grade === 1) return 0.007; // ca. 10 Minuten
+      if (grade === 2) return Math.max(1, Math.round(s * 0.85));
+      if (grade === 3) return Math.max(1, Math.round(s));
+      if (grade === 4) return Math.max(Math.round(s * 1.3), Math.round(s) + 1);
+      return 1;
+    }
+
+    function formatIntervalText(days) {
+      if (days <= 0.02) return '< 10 Min';
+      if (days < 1) return 'heute';
+      const roundDays = Math.round(days);
+      if (roundDays === 1) return '1 Tag';
+      if (roundDays < 30) return `${roundDays} Tage`;
+      if (roundDays < 365) {
+        const months = (days / 30).toFixed(days % 30 === 0 ? 0 : 1);
+        return `${months} Mon.`;
+      }
+      return `${(days / 365).toFixed(1)} J.`;
+    }
+
+    function isFsrsDue(cardData) {
+      if (!cardData || !cardData.reps || cardData.reps === 0) return true;
+      if (cardData.dueDate && cardData.dueDate <= Date.now()) return true;
+      const t = getElapsedDays(cardData.lastReview);
+      const r = calcRetrievability(t, cardData.s);
+      return r < FSRS_DESIRED_RETENTION;
+    }
+
+    // ==========================================
+    // LEITNER 5-BOX HELPERS
+    // ==========================================
     function getItemLevel(id) {
       return cardLevels[id] || 1;
     }
@@ -1920,9 +2116,41 @@
     }
 
     function updateMasteredHeader() {
-      const masteredCount = STILMITTEL_DATA.filter(item => (cardLevels[item.id] || 1) >= 5).length;
-      document.getElementById('globalMasteredStat').innerText = `${masteredCount} / ${STILMITTEL_DATA.length} gelernt`;
+      const isFsrs = cardAlgo === 'fsrs';
+      const headerStat = document.getElementById('globalMasteredStat');
+
+      if (isFsrs) {
+        const fsrsItems = Object.values(fsrsCards);
+        const stableCount = fsrsItems.filter(c => c && c.reps > 0 && c.s >= 14).length;
+        const dueCount = STILMITTEL_DATA.filter(item => isFsrsDue(fsrsCards[item.id])).length;
+        if (headerStat) {
+          headerStat.innerText = `${stableCount} / ${STILMITTEL_DATA.length} stabil (${dueCount} fällig)`;
+        }
+      } else {
+        const masteredCount = STILMITTEL_DATA.filter(item => (cardLevels[item.id] || 1) >= 5).length;
+        if (headerStat) {
+          headerStat.innerText = `${masteredCount} / ${STILMITTEL_DATA.length} gelernt`;
+        }
+      }
+
       updateQuizMistakesBadge();
+      updateQueueFilterOptions();
+    }
+
+    function updateQueueFilterOptions() {
+      const qSelect = document.getElementById('fsrsQueueFilter');
+      if (!qSelect) return;
+      const dueCount = STILMITTEL_DATA.filter(item => isFsrsDue(fsrsCards[item.id])).length;
+      const learningCount = STILMITTEL_DATA.filter(item => fsrsCards[item.id] && fsrsCards[item.id].reps > 0).length;
+      const newCount = STILMITTEL_DATA.filter(item => !fsrsCards[item.id] || !fsrsCards[item.id].reps).length;
+
+      const optDue = qSelect.querySelector('option[value="due"]');
+      const optLearning = qSelect.querySelector('option[value="learning"]');
+      const optNew = qSelect.querySelector('option[value="new"]');
+
+      if (optDue) optDue.innerText = `📅 Jetzt fällig (${dueCount})`;
+      if (optLearning) optLearning.innerText = `📈 In Wiederholung (${learningCount})`;
+      if (optNew) optNew.innerText = `🌱 Noch unberührt (${newCount})`;
     }
 
     function updateQuizMistakesBadge() {
@@ -1942,17 +2170,91 @@
       }
     }
 
+    function resetCardProgressPrompt() {
+      if (cardAlgo === 'fsrs') {
+        if (confirm('Möchtest du den FSRS-Lernverlauf (Stabilität, Schwierigkeit & Fälligkeiten) für alle Karten zurücksetzen?')) {
+          fsrsCards = {};
+          localStorage.removeItem('rhetorik_fsrs_cards');
+          applyCardFilters();
+          updateMasteredHeader();
+          showToast('FSRS-Lernverlauf zurückgesetzt!', 'fa-rotate-left');
+        }
+      } else {
+        resetLeitnerProgress();
+      }
+    }
+
     function resetLeitnerProgress() {
-      if (confirm('Möchtest du den Lernfortschritt für alle Karteikarten wirklich auf Kasten 1 zurücksetzen?')) {
+      if (confirm('Möchtest du den Leitner-Lernfortschritt für alle Karteikarten wirklich auf Kasten 1 zurücksetzen?')) {
         cardLevels = {};
         localStorage.removeItem('rhetorik_leitner_levels');
         applyCardFilters();
         updateMasteredHeader();
-        showToast('Lernstand zurückgesetzt!', 'fa-rotate-left');
+        showToast('Leitner-Lernstand zurückgesetzt!', 'fa-rotate-left');
       }
     }
 
+    function setSpacedRepetitionAlgo(algo) {
+      cardAlgo = algo;
+      localStorage.setItem('rhetorik_card_algo', cardAlgo);
+
+      const isFsrs = cardAlgo === 'fsrs';
+      const fsrsBtn = document.getElementById('algoFsrsBtn');
+      const leitnerBtn = document.getElementById('algoLeitnerBtn');
+      const title = document.getElementById('cardSectionTitle');
+      const badge = document.getElementById('algoHeaderBadge');
+      const subtitle = document.getElementById('cardSectionSubtitle');
+
+      const fsrsFilterWrap = document.getElementById('fsrsFilterWrap');
+      const leitnerFilterWrap = document.getElementById('leitnerFilterWrap');
+      const fsrsMetrics = document.getElementById('fsrsMetricsContainer');
+      const leitnerMetrics = document.getElementById('leitnerMetricsContainer');
+      const fsrsActions = document.getElementById('fsrsActionButtons');
+      const leitnerActions = document.getElementById('leitnerActionButtons');
+
+      if (isFsrs) {
+        if (fsrsBtn) fsrsBtn.className = 'px-2.5 sm:px-3 py-1.5 rounded-lg bg-white text-indigo-700 shadow-sm transition font-bold flex items-center gap-1.5';
+        if (leitnerBtn) leitnerBtn.className = 'px-2.5 sm:px-3 py-1.5 rounded-lg text-slate-600 hover:text-slate-900 transition font-semibold flex items-center gap-1.5';
+        if (title) title.innerHTML = '<i class="fa-solid fa-brain text-indigo-600"></i><span>FSRS-4.5 Karteikasten</span>';
+        if (badge) badge.innerText = 'Spaced Repetition';
+        if (subtitle) subtitle.innerText = 'Modernes 17-Parameter DSR-Modell (Retrievability, Stability, Difficulty) – 20–30 % weniger Wiederholungen bei 90 % Behaltungsquote.';
+        if (fsrsFilterWrap) fsrsFilterWrap.classList.remove('hidden');
+        if (leitnerFilterWrap) leitnerFilterWrap.classList.add('hidden');
+        if (fsrsMetrics) fsrsMetrics.classList.remove('hidden');
+        if (leitnerMetrics) leitnerMetrics.classList.add('hidden');
+        if (fsrsActions) fsrsActions.classList.remove('hidden');
+        if (leitnerActions) leitnerActions.classList.add('hidden');
+      } else {
+        if (fsrsBtn) fsrsBtn.className = 'px-2.5 sm:px-3 py-1.5 rounded-lg text-slate-600 hover:text-slate-900 transition font-semibold flex items-center gap-1.5';
+        if (leitnerBtn) leitnerBtn.className = 'px-2.5 sm:px-3 py-1.5 rounded-lg bg-white text-indigo-700 shadow-sm transition font-bold flex items-center gap-1.5';
+        if (title) title.innerHTML = '<i class="fa-solid fa-boxes-stacked text-indigo-600"></i><span>Leitner-Karteikarten (5-Kasten)</span>';
+        if (badge) badge.innerText = 'Klassisch';
+        if (subtitle) subtitle.innerText = 'Klassisches 5-Kasten-Lernsystem: Wische nach links (wiederholen) oder rechts (gekonnt).';
+        if (fsrsFilterWrap) fsrsFilterWrap.classList.add('hidden');
+        if (leitnerFilterWrap) leitnerFilterWrap.classList.remove('hidden');
+        if (fsrsMetrics) fsrsMetrics.classList.add('hidden');
+        if (leitnerMetrics) leitnerMetrics.classList.remove('hidden');
+        if (fsrsActions) fsrsActions.classList.add('hidden');
+        if (leitnerActions) leitnerActions.classList.remove('hidden');
+      }
+
+      applyCardFilters();
+      updateMasteredHeader();
+    }
+
+    function filterByFsrsQueue(queue) {
+      activeFsrsQueue = queue;
+      applyCardFilters();
+    }
+
+    function filterByLeitnerBox(box) {
+      activeLeitnerBox = box;
+      applyCardFilters();
+    }
+
     function applyCardFilters() {
+      const isFsrs = cardAlgo === 'fsrs';
+
       filteredCards = STILMITTEL_DATA.filter(item => {
         if (activeCardCategory === 'highlighted') {
           if (!item.highlighted) return false;
@@ -1962,14 +2264,33 @@
           return false;
         }
 
-        if (activeLeitnerBox !== 'all') {
-          const lvl = getItemLevel(item.id);
-          if (lvl.toString() !== activeLeitnerBox.toString()) return false;
+        if (isFsrs) {
+          const cardData = fsrsCards[item.id];
+          if (activeFsrsQueue === 'due') {
+            return isFsrsDue(cardData);
+          } else if (activeFsrsQueue === 'learning') {
+            return cardData && cardData.reps > 0;
+          } else if (activeFsrsQueue === 'new') {
+            return !cardData || !cardData.reps || cardData.reps === 0;
+          }
+          return true;
+        } else {
+          if (activeLeitnerBox !== 'all') {
+            const lvl = getItemLevel(item.id);
+            if (lvl.toString() !== activeLeitnerBox.toString()) return false;
+          }
+          return true;
         }
-        return true;
       });
 
       if (filteredCards.length === 0) {
+        if (isFsrs && activeFsrsQueue === 'due') {
+          showToast('Großartig! Alle fälligen Karten wurden wiederholt. Zeige alle.', 'fa-sparkles');
+          activeFsrsQueue = 'all';
+          const qSelect = document.getElementById('fsrsQueueFilter');
+          if (qSelect) qSelect.value = 'all';
+          return applyCardFilters();
+        }
         filteredCards = [...STILMITTEL_DATA];
       }
 
@@ -1989,17 +2310,12 @@
       applyCardFilters();
     }
 
-    function filterByLeitnerBox(box) {
-      activeLeitnerBox = box;
-      applyCardFilters();
-    }
-
     function renderCurrentCard() {
       if (filteredCards.length === 0) return;
       if (currentCardIndex >= filteredCards.length) currentCardIndex = 0;
 
       const item = filteredCards[currentCardIndex];
-      const level = getItemLevel(item.id);
+      const isFsrs = cardAlgo === 'fsrs';
 
       cardIsFlipped = false;
       const cardEl = document.getElementById('flashcardElement');
@@ -2010,14 +2326,82 @@
       document.getElementById('cardCounter').innerText = `Karte ${currentCardIndex + 1} von ${filteredCards.length}`;
       document.getElementById('cardProgressLabel').innerText = `Karte ${currentCardIndex + 1} von ${filteredCards.length} (${item.categoryLabel})`;
 
-      const boxNames = ['', 'Kasten 1 (Neu)', 'Kasten 2 (Aufbau)', 'Kasten 3 (Vertieft)', 'Kasten 4 (Fast sicher)', 'Kasten 5 (Gemeistert)'];
-      document.getElementById('cardBoxBadge').innerText = boxNames[level] || `Kasten ${level}`;
+      if (isFsrs) {
+        const cardData = getFsrsCard(item.id);
+        const t = getElapsedDays(cardData.lastReview);
+        const rVal = cardData.reps > 0 ? Math.round(calcRetrievability(t, cardData.s) * 100) : 100;
+        const sVal = cardData.s ? (cardData.s >= 10 ? cardData.s.toFixed(0) : cardData.s.toFixed(1)) : '0';
+        const dVal = cardData.d ? cardData.d.toFixed(1) : '-';
+        const due = isFsrsDue(cardData);
 
-      const dotsHtml = [1, 2, 3, 4, 5].map(i => {
-        const bg = i <= level ? 'bg-indigo-600' : 'bg-slate-200';
-        return `<span class="w-2.5 h-2.5 rounded-full ${bg} transition-colors"></span>`;
-      }).join('');
-      document.getElementById('leitnerBoxesVisual').innerHTML = dotsHtml;
+        // Update DSR Badges
+        const rBadge = document.getElementById('fsrsRetrievabilityBadge');
+        if (rBadge) {
+          rBadge.innerHTML = `<i class="fa-solid fa-gauge-high text-emerald-600"></i><span>R: ${rVal}%</span>`;
+          if (rVal >= 90) {
+            rBadge.className = 'px-2.5 py-0.5 rounded-lg bg-emerald-50 text-emerald-800 border border-emerald-200 font-extrabold flex items-center gap-1';
+          } else if (rVal >= 75) {
+            rBadge.className = 'px-2.5 py-0.5 rounded-lg bg-amber-50 text-amber-800 border border-amber-200 font-extrabold flex items-center gap-1';
+          } else {
+            rBadge.className = 'px-2.5 py-0.5 rounded-lg bg-rose-50 text-rose-800 border border-rose-200 font-extrabold flex items-center gap-1';
+          }
+        }
+
+        const sBadge = document.getElementById('fsrsStabilityBadge');
+        if (sBadge) {
+          sBadge.innerHTML = `<i class="fa-solid fa-calendar-day text-blue-500"></i><span>S: ${sVal} T</span>`;
+        }
+
+        const dBadge = document.getElementById('fsrsDifficultyBadge');
+        if (dBadge) {
+          dBadge.innerHTML = `<i class="fa-solid fa-weight-scale text-amber-500"></i><span>D: ${dVal}</span>`;
+        }
+
+        const dueBadge = document.getElementById('fsrsDueBadge');
+        if (dueBadge) {
+          if (!cardData.reps || cardData.reps === 0) {
+            dueBadge.className = 'px-2.5 py-0.5 rounded-lg bg-indigo-50 text-indigo-700 border border-indigo-200 font-extrabold flex items-center gap-1';
+            dueBadge.innerHTML = '<i class="fa-solid fa-seedling text-indigo-500"></i><span>Neu</span>';
+          } else if (due) {
+            dueBadge.className = 'px-2.5 py-0.5 rounded-lg bg-rose-50 text-rose-700 border border-rose-200 font-extrabold flex items-center gap-1';
+            dueBadge.innerHTML = '<i class="fa-solid fa-clock text-rose-500"></i><span>Fällig</span>';
+          } else {
+            dueBadge.className = 'px-2.5 py-0.5 rounded-lg bg-emerald-50 text-emerald-700 border border-emerald-200 font-extrabold flex items-center gap-1';
+            dueBadge.innerHTML = '<i class="fa-solid fa-check text-emerald-500"></i><span>Bereit</span>';
+          }
+        }
+
+        // Live calculation of next predicted intervals for all 4 ratings
+        const nextS1 = calcNextStability(cardData, 1, t);
+        const nextS2 = calcNextStability(cardData, 2, t);
+        const nextS3 = calcNextStability(cardData, 3, t);
+        const nextS4 = calcNextStability(cardData, 4, t);
+
+        const i1 = calcNextInterval(nextS1, 1);
+        const i2 = calcNextInterval(nextS2, 2);
+        const i3 = calcNextInterval(nextS3, 3);
+        const i4 = calcNextInterval(nextS4, 4);
+
+        const lbl1 = document.getElementById('fsrsIntervalAgain');
+        const lbl2 = document.getElementById('fsrsIntervalHard');
+        const lbl3 = document.getElementById('fsrsIntervalGood');
+        const lbl4 = document.getElementById('fsrsIntervalEasy');
+
+        if (lbl1) lbl1.innerText = formatIntervalText(i1);
+        if (lbl2) lbl2.innerText = `+${formatIntervalText(i2)}`;
+        if (lbl3) lbl3.innerText = `+${formatIntervalText(i3)}`;
+        if (lbl4) lbl4.innerText = `+${formatIntervalText(i4)}`;
+      } else {
+        const level = getItemLevel(item.id);
+        const boxNames = ['', 'Kasten 1 (Neu)', 'Kasten 2 (Aufbau)', 'Kasten 3 (Vertieft)', 'Kasten 4 (Fast sicher)', 'Kasten 5 (Gemeistert)'];
+        document.getElementById('cardBoxBadge').innerText = boxNames[level] || `Kasten ${level}`;
+
+        const dotsHtml = [1, 2, 3, 4, 5].map(i => {
+          const bg = i <= level ? 'bg-indigo-600' : 'bg-slate-200';
+          return `<span class="w-2.5 h-2.5 rounded-full ${bg} transition-colors"></span>`;
+        }).join('');
+        document.getElementById('leitnerBoxesVisual').innerHTML = dotsHtml;
+      }
 
       document.getElementById('cardBadgeFront').innerText = item.categoryLabel;
       document.getElementById('cardBackCategory').innerText = item.categoryLabel;
@@ -2067,6 +2451,60 @@
       playTone('flip');
     }
 
+    function rateFsrsCard(grade) {
+      if (filteredCards.length === 0) return;
+      const item = filteredCards[currentCardIndex];
+      const cardData = getFsrsCard(item.id);
+      const t = getElapsedDays(cardData.lastReview);
+
+      const nextS = calcNextStability(cardData, grade, t);
+      const nextD = (!cardData.reps || cardData.reps === 0) ? calcInitDifficulty(grade) : calcNextDifficulty(cardData.d, grade);
+      const intervalDays = calcNextInterval(nextS, grade);
+      const now = Date.now();
+      const nextDueDate = now + Math.round(intervalDays * 86400000);
+
+      const updatedCard = {
+        s: parseFloat(nextS.toFixed(4)),
+        d: parseFloat(nextD.toFixed(4)),
+        reps: (cardData.reps || 0) + 1,
+        lapses: grade === 1 ? (cardData.lapses || 0) + 1 : (cardData.lapses || 0),
+        lastReview: now,
+        dueDate: nextDueDate,
+        state: grade === 1 ? 3 : 2
+      };
+
+      fsrsCards[item.id] = updatedCard;
+      localStorage.setItem('rhetorik_fsrs_cards', JSON.stringify(fsrsCards));
+
+      const cardEl = document.getElementById('flashcardElement');
+      if (grade === 1) {
+        playTone('error');
+        addXP(5, 'FSRS: Noch üben');
+        cardEl.classList.add('swipe-left');
+        showToast(`„${item.term}“: Wiederholung ${formatIntervalText(intervalDays)}`, 'fa-rotate-left');
+      } else if (grade === 2) {
+        playTone('flip');
+        addXP(10, 'FSRS: Schwer');
+        showToast(`„${item.term}“: Wiederholung in ${formatIntervalText(intervalDays)}`, 'fa-clock');
+      } else if (grade === 3) {
+        playTone('success');
+        addXP(15, 'FSRS: Gut');
+        cardEl.classList.add('swipe-right');
+        showToast(`„${item.term}“: Wiederholung in ${formatIntervalText(intervalDays)}`, 'fa-check');
+      } else if (grade === 4) {
+        playTone('win');
+        addXP(20, 'FSRS: Perfekt!');
+        cardEl.classList.add('swipe-right');
+        showToast(`„${item.term}“: Wiederholung in ${formatIntervalText(intervalDays)}`, 'fa-wand-magic-sparkles');
+      }
+
+      updateMasteredHeader();
+
+      setTimeout(() => {
+        nextCard();
+      }, 250);
+    }
+
     function markCardMastered(isMastered) {
       if (filteredCards.length === 0) return;
       const item = filteredCards[currentCardIndex];
@@ -2125,7 +2563,7 @@
       renderCurrentCard();
     }
 
-    // Touch Swipe Gestures
+    // Touch Swipe Gestures (supports both FSRS and Leitner)
     let touchStartX = 0;
     let touchStartY = 0;
     const cardTouchContainer = document.getElementById('flashcardContainer');
@@ -2142,10 +2580,18 @@
       const diffY = touchEndY - touchStartY;
 
       if (Math.abs(diffX) > 50 && Math.abs(diffX) > Math.abs(diffY)) {
-        if (diffX > 0) {
-          markCardMastered(true);
+        if (cardAlgo === 'fsrs') {
+          if (diffX > 0) {
+            rateFsrsCard(3); // Gut
+          } else {
+            rateFsrsCard(1); // Nochmal
+          }
         } else {
-          markCardMastered(false);
+          if (diffX > 0) {
+            markCardMastered(true);
+          } else {
+            markCardMastered(false);
+          }
         }
       } else if (Math.abs(diffX) < 15 && Math.abs(diffY) < 15) {
         flipCard();
@@ -3424,9 +3870,11 @@
 
     function getSyncPayload() {
       return {
-        v: 1,
+        v: 2,
         timestamp: Date.now(),
+        algo: cardAlgo,
         levels: cardLevels,
+        fsrs: fsrsCards,
         mistakes: quizMistakes,
         stats: {
           maxStreak: quizMaxStreak
@@ -3453,8 +3901,18 @@
       const payload = getSyncPayload();
       const token = encodeSyncPayload(payload);
       
-      const masteredCount = STILMITTEL_DATA.filter(item => (cardLevels[item.id] || 1) >= 5).length;
-      document.getElementById('syncStatMastered').innerText = `${masteredCount} / ${STILMITTEL_DATA.length}`;
+      const isFsrs = cardAlgo === 'fsrs';
+      let masteredDisplay = '';
+      if (isFsrs) {
+        const fsrsItems = Object.values(fsrsCards);
+        const stableCount = fsrsItems.filter(c => c && c.reps > 0 && c.s >= 14).length;
+        masteredDisplay = `${stableCount} / ${STILMITTEL_DATA.length} stabil`;
+      } else {
+        const masteredCount = STILMITTEL_DATA.filter(item => (cardLevels[item.id] || 1) >= 5).length;
+        masteredDisplay = `${masteredCount} / ${STILMITTEL_DATA.length} (Kasten 5)`;
+      }
+
+      document.getElementById('syncStatMastered').innerText = masteredDisplay;
       document.getElementById('syncStatMistakes').innerText = `${quizMistakes.length}`;
       document.getElementById('syncStatStreak').innerText = `${quizMaxStreak}`;
 
@@ -3589,6 +4047,14 @@
         cardLevels = payload.levels;
         localStorage.setItem('rhetorik_leitner_levels', JSON.stringify(cardLevels));
       }
+      if (payload.fsrs && typeof payload.fsrs === 'object') {
+        fsrsCards = payload.fsrs;
+        localStorage.setItem('rhetorik_fsrs_cards', JSON.stringify(fsrsCards));
+      }
+      if (payload.algo && (payload.algo === 'leitner' || payload.algo === 'fsrs')) {
+        cardAlgo = payload.algo;
+        localStorage.setItem('rhetorik_card_algo', cardAlgo);
+      }
       if (Array.isArray(payload.mistakes)) {
         quizMistakes = payload.mistakes;
         localStorage.setItem('rhetorik_quiz_mistakes', JSON.stringify(quizMistakes));
@@ -3597,7 +4063,7 @@
         quizMaxStreak = Math.max(quizMaxStreak, payload.stats.maxStreak);
       }
 
-      applyCardFilters();
+      setSpacedRepetitionAlgo(cardAlgo);
       updateMasteredHeader();
       renderCurrentCard();
       showToast('Lernstand erfolgreich synchronisiert!', 'fa-arrows-rotate');
@@ -3608,9 +4074,14 @@
       if (hash && hash.startsWith('#sync=')) {
         const token = hash.replace('#sync=', '').trim();
         const payload = decodeSyncPayload(token);
-        if (payload && payload.levels) {
+        if (payload && (payload.levels || payload.fsrs)) {
           pendingIncomingSync = payload;
-          const masteredCount = STILMITTEL_DATA.filter(item => (payload.levels[item.id] || 1) >= 5).length;
+          let masteredCount = 0;
+          if (payload.algo === 'fsrs' && payload.fsrs) {
+            masteredCount = Object.values(payload.fsrs).filter(c => c && c.reps > 0 && c.s >= 14).length;
+          } else if (payload.levels) {
+            masteredCount = STILMITTEL_DATA.filter(item => (payload.levels[item.id] || 1) >= 5).length;
+          }
           document.getElementById('incomingSyncMastered').innerText = `${masteredCount} von ${STILMITTEL_DATA.length}`;
           document.getElementById('incomingSyncMistakes').innerText = `${(payload.mistakes || []).length}`;
           document.getElementById('incomingSyncStreak').innerText = `${(payload.stats && payload.stats.maxStreak) || 0}`;
@@ -3791,8 +4262,13 @@
     }
 
     function checkAchievements() {
-      const masteredCount = STILMITTEL_DATA.filter(item => (cardLevels[item.id] || 1) >= 5).length;
-      const klangMastered = STILMITTEL_DATA.filter(item => item.category === 'klang' && (cardLevels[item.id] || 1) >= 5).length;
+      function isMasteredCard(item) {
+        if ((cardLevels[item.id] || 1) >= 5) return true;
+        const c = fsrsCards[item.id];
+        return !!(c && c.reps >= 2 && c.s >= 14);
+      }
+      const masteredCount = STILMITTEL_DATA.filter(item => isMasteredCard(item)).length;
+      const klangMastered = STILMITTEL_DATA.filter(item => item.category === 'klang' && isMasteredCard(item)).length;
       const totalKlang = STILMITTEL_DATA.filter(item => item.category === 'klang').length;
 
       // 1. Erster Schritt
@@ -3992,10 +4468,14 @@
           nextCard();
         } else if (e.code === 'ArrowLeft') {
           prevCard();
-        } else if (e.key === '1') {
-          markCardMastered(false);
-        } else if (e.key === '2') {
-          markCardMastered(true);
+        } else if (cardAlgo === 'fsrs') {
+          if (e.key === '1') rateFsrsCard(1);
+          else if (e.key === '2') rateFsrsCard(2);
+          else if (e.key === '3') rateFsrsCard(3);
+          else if (e.key === '4') rateFsrsCard(4);
+        } else {
+          if (e.key === '1') markCardMastered(false);
+          else if (e.key === '2') markCardMastered(true);
         }
       } else if (currentTabIndex === 'quiz') {
         if (['1', '2', '3', '4'].includes(e.key)) {
@@ -4075,7 +4555,7 @@
 
     window.onload = function() {
       updateSoundUI();
-      applyCardFilters();
+      setSpacedRepetitionAlgo(cardAlgo);
       updateMasteredHeader();
       renderPrintCheatsheet();
       updateGamificationHeader();

www/sw.js

@@ -1,4 +1,4 @@
-const CACHE_NAME = 'rhetorikmaster-v10';
+const CACHE_NAME = 'rhetorikmaster-v11';
 const STATIC_ASSETS = [
   '/',
   '/index.html',