From 6369f319a86e34207ddfc3516d712771e1d8a5d6 Mon Sep 17 00:00:00 2001
From: Aditya8369 <mahajan2005aditya@gmail.com>
Date: Fri, 19 Jun 2026 15:08:57 +0530
Subject: [PATCH] Adaptive Quiz Difficulty

---
 quiz/adaptiveQuiz.js     | 145 ++++++++++++++++++++++++++++++++++
 quiz/motionquiz.html     |   3 +
 quiz/motionquiz.js       | 122 +++++++++++++++++++++++------
 quiz/nlmquiz.html        |   2 +
 quiz/nlmquiz.js          | 165 ++++++++++++++++++++++++++++++++-------
 quiz/projectilequiz.html |   2 +
 quiz/projectilequiz.js   |  17 ++--
 quiz/rayquiz.html        |   2 +
 8 files changed, 396 insertions(+), 62 deletions(-)
 create mode 100644 quiz/adaptiveQuiz.js

diff --git a/quiz/adaptiveQuiz.js b/quiz/adaptiveQuiz.js
new file mode 100644
index 0000000..3d8bed8
--- /dev/null
+++ b/quiz/adaptiveQuiz.js
@@ -0,0 +1,145 @@
+/**
+ * adaptiveQuiz.js
+ * Shared helper for Adaptive Quiz Difficulty (client-side only).
+ *
+ * Usage (per quiz page JS):
+ *   import/require is not used here (no bundler). Include this file via:
+ *     <script src="../quiz/adaptiveQuiz.js"></script>
+ *   Then call:
+ *     const adaptive = buildAdaptiveQuiz({ questions });
+ */
+
+(function () {
+  'use strict';
+
+  function normalizeDifficulty(d) {
+    const val = String(d || '').toLowerCase();
+    if (val === 'easy' || val === 'e') return 0;
+    if (val === 'medium' || val === 'med' || val === 'm') return 1;
+    if (val === 'hard' || val === 'h') return 2;
+
+    // Default: medium
+    return 1;
+  }
+
+  function clamp(n, min, max) {
+    return Math.max(min, Math.min(max, n));
+  }
+
+  /**
+   * Build a per-difficulty bucket of question copies.
+   * @param {Array<{difficulty?: string|number}>} questions
+   */
+  function buildBuckets(questions) {
+    const buckets = { 0: [], 1: [], 2: [] };
+    questions.forEach((q, idx) => {
+      const di = normalizeDifficulty(q.difficulty);
+      // keep original index for tracking
+      buckets[di].push({ ...q, __qid: idx });
+    });
+
+    // Shuffle each bucket for variety.
+    Object.keys(buckets).forEach(k => {
+      const arr = buckets[k];
+      for (let i = arr.length - 1; i > 0; i--) {
+        const j = Math.floor(Math.random() * (i + 1));
+        [arr[i], arr[j]] = [arr[j], arr[i]];
+      }
+    });
+
+    return buckets;
+  }
+
+  function createAdaptiveQuiz({ questions, startingDifficultyIndex = 1 }) {
+    const buckets = buildBuckets(questions);
+    const totalSteps = questions.length;
+
+    let difficultyIndex = clamp(startingDifficultyIndex, 0, 2);
+    let consecutiveCorrect = 0;
+    let consecutiveIncorrect = 0;
+
+    // Flattened remaining counts for quick fallback.
+    function countRemainingAt(di) {
+      return buckets[di].length;
+    }
+
+    function totalRemaining() {
+      return buckets[0].length + buckets[1].length + buckets[2].length;
+    }
+
+    /**
+     * Pick next question from the current difficulty if possible.
+     * Otherwise, fallback to nearest difficulty that still has questions.
+     */
+    function takeNext() {
+      if (totalRemaining() <= 0) return null;
+
+      // Try current difficulty first.
+      if (countRemainingAt(difficultyIndex) > 0) {
+        return buckets[difficultyIndex].shift();
+      }
+
+      // Fallback: nearest difficulty.
+      for (let dist = 1; dist <= 2; dist++) {
+        const lower = difficultyIndex - dist;
+        const upper = difficultyIndex + dist;
+        if (lower >= 0 && countRemainingAt(lower) > 0) return buckets[lower].shift();
+        if (upper <= 2 && countRemainingAt(upper) > 0) return buckets[upper].shift();
+      }
+
+      // Final fallback: any remaining.
+      for (let di = 0; di <= 2; di++) {
+        if (countRemainingAt(di) > 0) return buckets[di].shift();
+      }
+
+      return null;
+    }
+
+    /**
+     * Update difficulty after an answer.
+     */
+    function updateDifficulty({ isCorrect }) {
+      if (isCorrect) {
+        consecutiveCorrect += 1;
+        consecutiveIncorrect = 0;
+
+        // After 2 consecutive correct: go harder.
+        if (consecutiveCorrect >= 2) {
+          difficultyIndex = clamp(difficultyIndex + 1, 0, 2);
+          consecutiveCorrect = 0;
+        }
+      } else {
+        consecutiveIncorrect += 1;
+        consecutiveCorrect = 0;
+
+        // After 2 consecutive incorrect: go easier.
+        if (consecutiveIncorrect >= 2) {
+          difficultyIndex = clamp(difficultyIndex - 1, 0, 2);
+          consecutiveIncorrect = 0;
+        }
+      }
+
+      return difficultyIndex;
+    }
+
+    return {
+      takeNext,
+      updateDifficulty,
+      getDifficultyIndex: () => difficultyIndex,
+      getTotalSteps: () => totalSteps,
+    };
+  }
+
+  function getStartingDifficultyFromAccuracy({ accuracy }) {
+    if (typeof accuracy !== 'number' || !isFinite(accuracy)) return 1; // medium
+    if (accuracy >= 0.8) return 2; // hard
+    if (accuracy <= 0.5) return 0; // easy
+    return 1; // medium
+  }
+
+  // Export to window.
+  window.createAdaptiveQuiz = createAdaptiveQuiz;
+  window.getStartingDifficultyFromAccuracy = getStartingDifficultyFromAccuracy;
+
+})();
+
diff --git a/quiz/motionquiz.html b/quiz/motionquiz.html
index d2cca23..ae7b58a 100644
--- a/quiz/motionquiz.html
+++ b/quiz/motionquiz.html
@@ -63,8 +63,11 @@ <h2 id="result-title" tabindex="-1">🎉 Quiz Completed!</h2>
     </div>
 
     <script src="../../quizProgress.js"></script>
+    <script src="adaptiveQuiz.js"></script>
+
     <script src="motionquiz.js"></script>
 
+
     <script>
       (function () {
         if (!('serviceWorker' in navigator)) return;
diff --git a/quiz/motionquiz.js b/quiz/motionquiz.js
index fbbaa78..5172223 100644
--- a/quiz/motionquiz.js
+++ b/quiz/motionquiz.js
@@ -1,18 +1,20 @@
 const questions = [
-    { question: "What is the SI unit of speed?", options: ["m/s", "km/h", "m/s²", "N"], answer: "m/s" },
-    { question: "What causes an object to accelerate?", options: ["Mass", "Force", "Friction", "Temperature"], answer: "Force" },
-    { question: "Which of these is a scalar quantity?", options: ["Velocity", "Acceleration", "Displacement", "Speed"], answer: "Speed" },
-    { question: "What does Newton's First Law state?", options: ["F = ma", "Action = Reaction", "Objects stay in motion/rest unless acted on", "Momentum is conserved"], answer: "Objects stay in motion/rest unless acted on" },
-    { question: "What is the formula for acceleration?", options: ["v/t", "d/t", "Δv/t", "F/m"], answer: "Δv/t" }
+    { difficulty: "easy", question: "What is the SI unit of speed?", options: ["m/s", "km/h", "m/s²", "N"], answer: "m/s" },
+    { difficulty: "easy", question: "What causes an object to accelerate?", options: ["Mass", "Force", "Friction", "Temperature"], answer: "Force" },
+    { difficulty: "medium", question: "Which of these is a scalar quantity?", options: ["Velocity", "Acceleration", "Displacement", "Speed"], answer: "Speed" },
+    { difficulty: "medium", question: "What does Newton's First Law state?", options: ["F = ma", "Action = Reaction", "Objects stay in motion/rest unless acted on", "Momentum is conserved"], answer: "Objects stay in motion/rest unless acted on" },
+    { difficulty: "hard", question: "What is the formula for acceleration?", options: ["v/t", "d/t", "Δv/t", "F/m"], answer: "Δv/t" }
 ];
 
-let currentQuestionIndex = 0;
+let adaptiveQuiz = null;
+let adaptiveSteps = [];
+let currentStepIndex = 0;
 let score = 0;
 let selectedOption = null;
-let userAnswers = new Array(questions.length).fill(null);
-
+let userSelectionsByStep = [];
 let lastFocusedEl = null;
 
+
 function getSrStatus() {
     return document.getElementById("sr-status");
 }
@@ -28,10 +30,16 @@ function focusMainResultHeading() {
     if (heading) heading.focus();
 }
 
+function currentQuestion() {
+    return adaptiveSteps[currentStepIndex];
+}
+
 function loadQuestion() {
     lastFocusedEl = document.activeElement;
 
-    let questionData = questions[currentQuestionIndex];
+    const questionData = currentQuestion();
+    if (!questionData) return;
+
     document.getElementById("question").textContent = questionData.question;
 
     let optionsContainer = document.getElementById("options");
@@ -51,18 +59,31 @@ function loadQuestion() {
         optionsContainer.appendChild(btn);
     });
 
-    selectedOption = null;
+    selectedOption = userSelectionsByStep[currentStepIndex] || null;
+
+    // Reflect selected option back into UI if navigating back.
+    if (selectedOption) {
+        document.querySelectorAll(".option").forEach(btn => {
+            const t = btn.textContent;
+            if (t === selectedOption) {
+                btn.classList.add("selected");
+                btn.setAttribute("aria-checked", "true");
+            }
+        });
+    }
 
-    document.getElementById("next-btn").disabled = true;
-    document.getElementById("prev-btn").disabled = currentQuestionIndex === 0;
-    document.getElementById("submit-btn").classList.toggle("hidden", currentQuestionIndex !== questions.length - 1);
-    document.getElementById("next-btn").classList.toggle("hidden", currentQuestionIndex === questions.length - 1);
+    const lastStep = adaptiveSteps.length - 1;
+    document.getElementById("next-btn").disabled = !selectedOption;
+    document.getElementById("prev-btn").disabled = currentStepIndex === 0;
+    document.getElementById("submit-btn").classList.toggle("hidden", currentStepIndex !== lastStep);
+    document.getElementById("next-btn").classList.toggle("hidden", currentStepIndex === lastStep);
 
     updateProgressBar();
 
-    announce(`Question ${currentQuestionIndex + 1} of ${questions.length}. ${questionData.question}`);
+    announce(`Question ${currentStepIndex + 1} of ${adaptiveSteps.length}. ${questionData.question}`);
 }
 
+
 function selectOption(button, option) {
     document.querySelectorAll(".option").forEach(btn => {
         btn.classList.remove("selected");
@@ -73,7 +94,8 @@ function selectOption(button, option) {
     button.setAttribute("aria-checked", "true");
 
     selectedOption = option;
-    userAnswers[currentQuestionIndex] = option;
+
+    userSelectionsByStep[currentStepIndex] = option;
 
     document.getElementById("next-btn").disabled = false;
     announce(`Selected: ${option}`);
@@ -85,14 +107,23 @@ function nextQuestion() {
         return;
     }
 
-    const isCorrect = selectedOption === questions[currentQuestionIndex].answer;
+    const q = currentQuestion();
+    const isCorrect = selectedOption === q.answer;
     if (isCorrect) score++;
 
+    userAnswers[currentStepIndex] = isCorrect;
+
     announce(isCorrect ? "Correct answer." : "Incorrect answer.");
 
-    currentQuestionIndex++;
+    if (adaptiveQuiz) {
+        adaptiveQuiz.updateDifficulty({ isCorrect });
+        if (currentStepIndex + 1 < adaptiveSteps.length) {
+            adaptiveSteps[currentStepIndex + 1] = adaptiveQuiz.takeNext();
+        }
+    }
 
-    if (currentQuestionIndex < questions.length) {
+    currentStepIndex++;
+    if (currentStepIndex < adaptiveSteps.length) {
         loadQuestion();
     } else {
         showResults();
@@ -100,10 +131,12 @@ function nextQuestion() {
 }
 
 function prevQuestion() {
-    currentQuestionIndex--;
+    currentStepIndex--;
+    selectedOption = userSelectionsByStep[currentStepIndex] || null;
     loadQuestion();
 }
 
+
 function confirmSubmit() {
     lastFocusedEl = document.activeElement;
     document.getElementById("confirm-popup").style.display = "block";
@@ -128,16 +161,19 @@ function submitQuiz() {
 }
 
 function restartQuiz() {
-    currentQuestionIndex = 0;
+    // reset adaptive session state
+    currentStepIndex = 0;
     score = 0;
     selectedOption = null;
-    userAnswers.fill(null);
+    userAnswers = new Array(adaptiveSteps.length).fill(null);
+    userSelectionsByStep = new Array(adaptiveSteps.length).fill(null);
 
     document.getElementById("quiz-box").classList.remove("hidden");
     document.getElementById("result-box").classList.add("hidden");
 
     document.getElementById("progress-bar").style.width = "0%";
 
+    startAdaptiveSession();
     loadQuestion();
 
     setTimeout(() => {
@@ -146,6 +182,7 @@ function restartQuiz() {
     }, 0);
 }
 
+
 function showPopup() {
     lastFocusedEl = document.activeElement;
     document.getElementById("popup").style.display = "block";
@@ -166,7 +203,7 @@ function closeConfirmPopup() {
 
 function showResults() {
     const finishAt = Date.now();
-    const totalQuestions = questions.length;
+    const totalQuestions = adaptiveSteps.length;
     const totalScore = score;
     const correctCount = score;
     const startAt = window.__quizMotionStartedAt || finishAt;
@@ -193,8 +230,8 @@ function showResults() {
     let scoreText = `You scored <strong>${totalScore}</strong> out of ${totalQuestions}! 🎉`;
     let feedbackHTML = "";
 
-    questions.forEach((q, index) => {
-        let userAnswer = userAnswers[index] || "No answer selected";
+    adaptiveSteps.forEach((q, index) => {
+        let userAnswer = userSelectionsByStep[index] || "No answer selected";
         let isCorrect = userAnswer === q.answer;
 
         feedbackHTML += `
@@ -213,9 +250,44 @@ function showResults() {
     focusMainResultHeading();
 }
 
+
+function startAdaptiveSession() {
+    let startingDi = 1;
+    try {
+        if (window.quizProgress && typeof window.quizProgress.getTopicStats === "function") {
+            const stats = window.quizProgress.getTopicStats("physics-motion");
+            const accuracy = stats?.questionsTotal > 0 ? stats.correctTotal / stats.questionsTotal : null;
+            if (window.getStartingDifficultyFromAccuracy) {
+                startingDi = window.getStartingDifficultyFromAccuracy({ accuracy });
+            }
+        }
+    } catch (e) {
+        // ignore
+    }
+
+    if (!window.createAdaptiveQuiz) {
+        adaptiveQuiz = null;
+        adaptiveSteps = questions.map(q => ({ ...q }));
+        currentStepIndex = 0;
+        userAnswers = new Array(adaptiveSteps.length).fill(null);
+        userSelectionsByStep = new Array(adaptiveSteps.length).fill(null);
+        return;
+    }
+
+    adaptiveQuiz = window.createAdaptiveQuiz({ questions, startingDifficultyIndex: startingDi });
+    adaptiveSteps = new Array(questions.length).fill(null);
+    currentStepIndex = 0;
+    userAnswers = new Array(questions.length).fill(null);
+    userSelectionsByStep = new Array(questions.length).fill(null);
+
+    adaptiveSteps[0] = adaptiveQuiz.takeNext();
+}
+
 document.addEventListener("DOMContentLoaded", () => {
     window.__quizMotionStartedAt = Date.now();
     document.getElementById("progress-bar").style.width = "0%";
+    startAdaptiveSession();
     loadQuestion();
 });
 
+
diff --git a/quiz/nlmquiz.html b/quiz/nlmquiz.html
index f5caeb4..8477ae3 100644
--- a/quiz/nlmquiz.html
+++ b/quiz/nlmquiz.html
@@ -65,8 +65,10 @@ <h2 id="result-title" tabindex="-1">🎉 Quiz Completed!</h2>
     </div>
 
     <script src="../../quizProgress.js"></script>
+    <script src="adaptiveQuiz.js"></script>
     <script src="nlmquiz.js"></script>
 
+
     <script>
       (function () {
         if (!('serviceWorker' in navigator)) return;
diff --git a/quiz/nlmquiz.js b/quiz/nlmquiz.js
index d740c85..b935827 100644
--- a/quiz/nlmquiz.js
+++ b/quiz/nlmquiz.js
@@ -1,24 +1,65 @@
 const questions = [
-    { question: "What does Newton's First Law state?", options: ["F = ma", "Action = Reaction", "Objects stay in motion/rest unless acted on", "Momentum is conserved"], answer: "Objects stay in motion/rest unless acted on" },
-    { question: "Which force is required to change the state of motion of an object?", options: ["Friction", "Gravity", "Applied Force", "Centripetal Force"], answer: "Applied Force" },
-    { question: "Newton's Second Law states that force is equal to:", options: ["mass × acceleration", "mass × velocity", "momentum × time", "velocity × time"], answer: "mass × acceleration" },
-    { question: "What happens when two equal and opposite forces act on an object?", options: ["The object moves in the direction of the larger force", "The object accelerates", "The object remains in equilibrium", "The object gains momentum"], answer: "The object remains in equilibrium" },
-    { question: "According to Newton’s Third Law, what happens when you push on a wall?", options: ["The wall moves", "The wall exerts an equal force back on you", "No force is applied back", "Only you experience the force"], answer: "The wall exerts an equal force back on you" },
-    { question: "What is inertia?", options: ["The tendency of an object to resist a change in motion", "The force applied by a moving object", "The acceleration of an object due to gravity", "The energy stored in a moving object"], answer: "The tendency of an object to resist a change in motion" },
-    { question: "If an object's mass increases, what happens to the force required to accelerate it?", options: ["Increases", "Decreases", "Remains the same", "Depends on velocity"], answer: "Increases" },
-    { question: "Which of the following is an example of Newton’s Third Law?", options: ["A car accelerating when force is applied", "A book resting on a table", "A rocket launching by expelling gases", "An object staying at rest"], answer: "A rocket launching by expelling gases" }
+    { difficulty: "easy", question: "What does Newton's First Law state?", options: ["F = ma", "Action = Reaction", "Objects stay in motion/rest unless acted on", "Momentum is conserved"], answer: "Objects stay in motion/rest unless acted on" },
+    { difficulty: "easy", question: "Which force is required to change the state of motion of an object?", options: ["Friction", "Gravity", "Applied Force", "Centripetal Force"], answer: "Applied Force" },
+    { difficulty: "medium", question: "Newton's Second Law states that force is equal to:", options: ["mass × acceleration", "mass × velocity", "momentum × time", "velocity × time"], answer: "mass × acceleration" },
+    { difficulty: "medium", question: "What happens when two equal and opposite forces act on an object?", options: ["The object moves in the direction of the larger force", "The object accelerates", "The object remains in equilibrium", "The object gains momentum"], answer: "The object remains in equilibrium" },
+    { difficulty: "medium", question: "According to Newton’s Third Law, what happens when you push on a wall?", options: ["The wall moves", "The wall exerts an equal force back on you", "No force is applied back", "Only you experience the force"], answer: "The wall exerts an equal force back on you" },
+    { difficulty: "medium", question: "What is inertia?", options: ["The tendency of an object to resist a change in motion", "The force applied by a moving object", "The acceleration of an object due to gravity", "The energy stored in a moving object"], answer: "The tendency of an object to resist a change in motion" },
+    { difficulty: "hard", question: "If an object's mass increases, what happens to the force required to accelerate it?", options: ["Increases", "Decreases", "Remains the same", "Depends on velocity"], answer: "Increases" },
+    { difficulty: "hard", question: "Which of the following is an example of Newton’s Third Law?", options: ["A car accelerating when force is applied", "A book resting on a table", "A rocket launching by expelling gases", "An object staying at rest"], answer: "A rocket launching by expelling gases" }
 ];
 
-let currentQuestionIndex = 0;
+let adaptiveQuiz = null;
+let adaptiveSteps = [];
+let currentStepIndex = 0;
 let score = 0;
 let selectedOption = null;
-let userAnswers = new Array(questions.length).fill(null);
+let userAnswers = [];
+let userSelectionsByStep = [];
+
 let lastFocusedEl = null;
 
+function startAdaptiveSession() {
+    // Determine starting difficulty from past topic accuracy.
+    let startingDi = 1;
+    try {
+        if (window.quizProgress && typeof window.quizProgress.getTopicStats === "function") {
+            const stats = window.quizProgress.getTopicStats("physics-nlm");
+            const accuracy = stats?.questionsTotal > 0 ? stats.correctTotal / stats.questionsTotal : null;
+            if (window.getStartingDifficultyFromAccuracy) {
+                startingDi = window.getStartingDifficultyFromAccuracy({ accuracy });
+            }
+        }
+    } catch (e) {
+        // ignore
+    }
+
+    if (!window.createAdaptiveQuiz) {
+        // Fallback: non-adaptive.
+        adaptiveQuiz = null;
+        adaptiveSteps = questions.map(q => ({ ...q }));
+        currentStepIndex = 0;
+        userAnswers = new Array(adaptiveSteps.length).fill(null);
+        userSelectionsByStep = new Array(adaptiveSteps.length).fill(null);
+        return;
+    }
+
+    adaptiveQuiz = window.createAdaptiveQuiz({ questions, startingDifficultyIndex: startingDi });
+    adaptiveSteps = new Array(questions.length).fill(null);
+    currentStepIndex = 0;
+    userAnswers = new Array(questions.length).fill(null);
+    userSelectionsByStep = new Array(questions.length).fill(null);
+
+    // Fill initial first question.
+    adaptiveSteps[0] = adaptiveQuiz.takeNext();
+}
+
+
 function getSrStatus() {
     return document.getElementById("sr-status");
 }
 
+
 function announce(message) {
     const el = getSrStatus();
     if (!el) return;
@@ -30,24 +71,27 @@ function focusMainResultHeading() {
     if (heading) heading.focus();
 }
 
+function currentQuestion() {
+    return adaptiveSteps[currentStepIndex];
+}
+
 function loadQuestion() {
     lastFocusedEl = document.activeElement;
 
-    let questionData = questions[currentQuestionIndex];
+    const questionData = currentQuestion();
+    if (!questionData) return;
+
     document.getElementById("question").textContent = questionData.question;
 
     let optionsContainer = document.getElementById("options");
     optionsContainer.innerHTML = "";
 
-    // Use button elements as options. Keep native keyboard handling.
     questionData.options.forEach(option => {
         let btn = document.createElement("button");
         btn.classList.add("option");
         btn.type = "button";
         btn.textContent = option;
 
-        // ARIA: map selection to radiogroup semantics.
-        // When user navigates with Tab/Shift+Tab, screen readers get current selection.
         btn.setAttribute("role", "radio");
         btn.setAttribute("aria-checked", "false");
         btn.onclick = () => selectOption(btn, option);
@@ -56,16 +100,19 @@ function loadQuestion() {
     });
 
     selectedOption = null;
+
+    const lastStep = adaptiveSteps.length - 1;
     document.getElementById("next-btn").disabled = true;
-    document.getElementById("prev-btn").disabled = currentQuestionIndex === 0;
-    document.getElementById("submit-btn").classList.toggle("hidden", currentQuestionIndex !== questions.length - 1);
-    document.getElementById("next-btn").classList.toggle("hidden", currentQuestionIndex === questions.length - 1);
+    document.getElementById("prev-btn").disabled = currentStepIndex === 0;
+    document.getElementById("submit-btn").classList.toggle("hidden", currentStepIndex !== lastStep);
+    document.getElementById("next-btn").classList.toggle("hidden", currentStepIndex === lastStep);
 
     updateProgressBar();
 
-    announce(`Question ${currentQuestionIndex + 1} of ${questions.length}. ${questionData.question}`);
+    announce(`Question ${currentStepIndex + 1} of ${adaptiveSteps.length}. ${questionData.question}`);
 }
 
+
 function selectOption(button, option) {
     document.querySelectorAll(".option").forEach(btn => {
         btn.classList.remove("selected");
@@ -76,7 +123,8 @@ function selectOption(button, option) {
     button.setAttribute("aria-checked", "true");
 
     selectedOption = option;
-    userAnswers[currentQuestionIndex] = option;
+
+    userSelectionsByStep[currentStepIndex] = option;
 
     document.getElementById("next-btn").disabled = false;
     announce(`Selected: ${option}`);
@@ -88,13 +136,25 @@ function nextQuestion() {
         return;
     }
 
-    const isCorrect = selectedOption === questions[currentQuestionIndex].answer;
+    const q = currentQuestion();
+    const isCorrect = selectedOption === q.answer;
     if (isCorrect) score++;
 
+    userAnswers[currentStepIndex] = isCorrect;
+
     announce(isCorrect ? "Correct answer." : "Incorrect answer.");
 
-    currentQuestionIndex++;
-    if (currentQuestionIndex < questions.length) {
+    // Update difficulty for subsequent questions.
+    if (adaptiveQuiz) {
+        adaptiveQuiz.updateDifficulty({ isCorrect });
+        if (currentStepIndex + 1 < adaptiveSteps.length) {
+            // Determine next question based on updated difficulty.
+            adaptiveSteps[currentStepIndex + 1] = adaptiveQuiz.takeNext();
+        }
+    }
+
+    currentStepIndex++;
+    if (currentStepIndex < adaptiveSteps.length) {
         loadQuestion();
     } else {
         showResults();
@@ -102,10 +162,13 @@ function nextQuestion() {
 }
 
 function prevQuestion() {
-    currentQuestionIndex--;
+    // Keep the navigation simple: go back one step, do not re-run difficulty.
+    currentStepIndex--;
+    selectedOption = userSelectionsByStep[currentStepIndex] || null;
     loadQuestion();
 }
 
+
 function confirmSubmit() {
     lastFocusedEl = document.activeElement;
     document.getElementById("confirm-popup").style.display = "block";
@@ -131,25 +194,28 @@ function submitQuiz() {
 }
 
 function restartQuiz() {
-    currentQuestionIndex = 0;
+    currentStepIndex = 0;
     score = 0;
     selectedOption = null;
-    userAnswers.fill(null);
+    userAnswers = new Array(adaptiveSteps.length).fill(null);
+    userSelectionsByStep = new Array(adaptiveSteps.length).fill(null);
 
     document.getElementById("quiz-box").classList.remove("hidden");
     document.getElementById("result-box").classList.add("hidden");
 
     document.getElementById("progress-bar").style.width = "0%";
 
+    // rebuild adaptive quiz session
+    startAdaptiveSession();
     loadQuestion();
 
-    // Focus first option after load.
     setTimeout(() => {
         const firstOption = document.querySelector("#options .option");
         if (firstOption) firstOption.focus();
     }, 0);
 }
 
+
 function showPopup() {
     lastFocusedEl = document.activeElement;
     document.getElementById("popup").style.display = "block";
@@ -170,7 +236,7 @@ function closeConfirmPopup() {
 
 function showResults() {
     const finishAt = Date.now();
-    const totalQuestions = questions.length;
+    const totalQuestions = adaptiveSteps.length;
     const totalScore = score;
     const correctCount = score;
     const startAt = window.__quizNlmStartedAt || finishAt;
@@ -197,8 +263,8 @@ function showResults() {
     let scoreText = `You scored <strong>${totalScore}</strong> out of ${totalQuestions}! 🎉`;
     let feedbackHTML = "";
 
-    questions.forEach((q, index) => {
-        let userAnswer = userAnswers[index] || "No answer selected";
+    adaptiveSteps.forEach((q, index) => {
+        let userAnswer = userSelectionsByStep[index] || "No answer selected";
         let isCorrect = userAnswer === q.answer;
 
         feedbackHTML += `
@@ -217,14 +283,53 @@ function showResults() {
     focusMainResultHeading();
 }
 
+
 function updateProgressBar() {
-    let progress = ((currentQuestionIndex + 1) / questions.length) * 100;
+    let progress = ((currentStepIndex + 1) / adaptiveSteps.length) * 100;
     document.getElementById("progress-bar").style.width = progress + "%";
 }
 
+function startAdaptiveSession() {
+    // Determine starting difficulty from past topic accuracy.
+    let startingDi = 1;
+    try {
+        if (window.quizProgress && typeof window.quizProgress.getTopicStats === 'function') {
+            const stats = window.quizProgress.getTopicStats('physics-nlm');
+            const accuracy = stats?.questionsTotal > 0 ? (stats.correctTotal / stats.questionsTotal) : null;
+            if (window.getStartingDifficultyFromAccuracy) {
+                startingDi = window.getStartingDifficultyFromAccuracy({ accuracy });
+            }
+        }
+    } catch (e) {
+        // ignore
+    }
+
+    if (!window.createAdaptiveQuiz) {
+        // Fallback: non-adaptive.
+        adaptiveQuiz = null;
+        adaptiveSteps = questions.map(q => ({ ...q }));
+        currentStepIndex = 0;
+        userAnswers = new Array(adaptiveSteps.length).fill(null);
+        userSelectionsByStep = new Array(adaptiveSteps.length).fill(null);
+        return;
+    }
+
+    adaptiveQuiz = window.createAdaptiveQuiz({ questions, startingDifficultyIndex: startingDi });
+    adaptiveSteps = new Array(questions.length).fill(null);
+    currentStepIndex = 0;
+    userAnswers = new Array(questions.length).fill(null);
+    userSelectionsByStep = new Array(questions.length).fill(null);
+
+    // Fill initial first question.
+    adaptiveSteps[0] = adaptiveQuiz.takeNext();
+    // Remaining questions will be determined as user answers.
+}
+
 document.addEventListener("DOMContentLoaded", () => {
     window.__quizNlmStartedAt = Date.now();
     document.getElementById("progress-bar").style.width = "0%";
+    startAdaptiveSession();
     loadQuestion();
 });
 
+
diff --git a/quiz/projectilequiz.html b/quiz/projectilequiz.html
index 11fd05d..cfc2369 100644
--- a/quiz/projectilequiz.html
+++ b/quiz/projectilequiz.html
@@ -51,7 +51,9 @@ <h2>🎉 Quiz Completed!</h2>
         </div>
     </div>
 
+    <script src="adaptiveQuiz.js"></script>
     <script src="projectilequiz.js"></script>
+
 </body>
 
 </html>
\ No newline at end of file
diff --git a/quiz/projectilequiz.js b/quiz/projectilequiz.js
index 24a7ba5..bca88b4 100644
--- a/quiz/projectilequiz.js
+++ b/quiz/projectilequiz.js
@@ -1,15 +1,18 @@
 const questions = [
-    { question: "What is the path of a projectile in ideal conditions?", options: ["Straight line", "Circular", "Parabolic", "Elliptical"], answer: "Parabolic" },
-    { question: "What is the horizontal acceleration of a projectile in the absence of air resistance?", options: ["9.8 m/s²", "0 m/s²", "Depends on initial velocity", "Constant"], answer: "0 m/s²" },
-    { question: "At the highest point of its trajectory, what is the vertical velocity of a projectile?", options: ["Maximum", "Zero", "Equal to initial velocity", "Depends on mass"], answer: "Zero" },
-    { question: "Which factor affects the range of a projectile the most?", options: ["Mass", "Launch angle", "Time of flight", "Shape"], answer: "Launch angle" },
-    { question: "What is the optimal angle for maximum range in projectile motion (neglecting air resistance)?", options: ["30°", "45°", "60°", "90°"], answer: "45°" }
+    { difficulty: "easy", question: "What is the path of a projectile in ideal conditions?", options: ["Straight line", "Circular", "Parabolic", "Elliptical"], answer: "Parabolic" },
+    { difficulty: "easy", question: "What is the horizontal acceleration of a projectile in the absence of air resistance?", options: ["9.8 m/s²", "0 m/s²", "Depends on initial velocity", "Constant"], answer: "0 m/s²" },
+    { difficulty: "medium", question: "At the highest point of its trajectory, what is the vertical velocity of a projectile?", options: ["Maximum", "Zero", "Equal to initial velocity", "Depends on mass"], answer: "Zero" },
+    { difficulty: "medium", question: "Which factor affects the range of a projectile the most?", options: ["Mass", "Launch angle", "Time of flight", "Shape"], answer: "Launch angle" },
+    { difficulty: "hard", question: "What is the optimal angle for maximum range in projectile motion (neglecting air resistance)?", options: ["30°", "45°", "60°", "90°"], answer: "45°" }
 ];
 
-let currentQuestionIndex = 0;
+let adaptiveQuiz = null;
+let adaptiveSteps = [];
+let currentStepIndex = 0;
 let score = 0;
 let selectedOption = null;
-let userAnswers = new Array(questions.length).fill(null);
+let userSelectionsByStep = [];
+
 
 function loadQuestion() {
     let questionData = questions[currentQuestionIndex];
diff --git a/quiz/rayquiz.html b/quiz/rayquiz.html
index 3e700ec..cd294ad 100644
--- a/quiz/rayquiz.html
+++ b/quiz/rayquiz.html
@@ -51,7 +51,9 @@ <h2>🎉 Quiz Completed!</h2>
         </div>
     </div>
 
+    <script src="adaptiveQuiz.js"></script>
     <script src="rayquiz.js"></script>
+
 </body>
 
 </html>
\ No newline at end of file