diff --git a/public/css/tractatus-theme.css b/public/css/tractatus-theme.css
index 498eee47..56f37d69 100644
--- a/public/css/tractatus-theme.css
+++ b/public/css/tractatus-theme.css
@@ -823,6 +823,112 @@ h3 { letter-spacing: -0.015em; }
   text-decoration: underline;
 }
 
+/* ========================================
+ * SCROLL ANIMATIONS
+ * Intersection Observer-based scroll animations
+ * ======================================== */
+
+/* Scroll animation initial states (before visible) */
+.animate-on-scroll {
+  transition: opacity 0.6s cubic-bezier(0.4, 0, 0.2, 1),
+              transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
+}
+
+/* Fade in animation */
+.animate-on-scroll[data-animation="fade-in"] {
+  opacity: 0;
+}
+
+.animate-on-scroll[data-animation="fade-in"].is-visible {
+  opacity: 1;
+}
+
+/* Slide up animation */
+.animate-on-scroll[data-animation="slide-up"] {
+  opacity: 0;
+  transform: translateY(2rem);
+}
+
+.animate-on-scroll[data-animation="slide-up"].is-visible {
+  opacity: 1;
+  transform: translateY(0);
+}
+
+/* Slide down animation */
+.animate-on-scroll[data-animation="slide-down"] {
+  opacity: 0;
+  transform: translateY(-2rem);
+}
+
+.animate-on-scroll[data-animation="slide-down"].is-visible {
+  opacity: 1;
+  transform: translateY(0);
+}
+
+/* Slide left animation */
+.animate-on-scroll[data-animation="slide-left"] {
+  opacity: 0;
+  transform: translateX(2rem);
+}
+
+.animate-on-scroll[data-animation="slide-left"].is-visible {
+  opacity: 1;
+  transform: translateX(0);
+}
+
+/* Slide right animation */
+.animate-on-scroll[data-animation="slide-right"] {
+  opacity: 0;
+  transform: translateX(-2rem);
+}
+
+.animate-on-scroll[data-animation="slide-right"].is-visible {
+  opacity: 1;
+  transform: translateX(0);
+}
+
+/* Scale in animation */
+.animate-on-scroll[data-animation="scale-in"] {
+  opacity: 0;
+  transform: scale(0.95);
+}
+
+.animate-on-scroll[data-animation="scale-in"].is-visible {
+  opacity: 1;
+  transform: scale(1);
+}
+
+/* Rotate in animation */
+.animate-on-scroll[data-animation="rotate-in"] {
+  opacity: 0;
+  transform: rotate(12deg) scale(0.95);
+}
+
+.animate-on-scroll[data-animation="rotate-in"].is-visible {
+  opacity: 1;
+  transform: rotate(0deg) scale(1);
+}
+
+/* Default animation if no data-animation specified */
+.animate-on-scroll:not([data-animation]) {
+  opacity: 0;
+  transform: translateY(2rem);
+}
+
+.animate-on-scroll:not([data-animation]).is-visible {
+  opacity: 1;
+  transform: translateY(0);
+}
+
+/* Respect user's motion preferences for scroll animations */
+@media (prefers-reduced-motion: reduce) {
+  .animate-on-scroll {
+    opacity: 1 !important;
+    transform: none !important;
+    transition: none !important;
+  }
+}
+
 /* ========================================
  * DARK MODE SUPPORT (Future)
  * Placeholder for dark mode implementation
diff --git a/public/index.html b/public/index.html
index d25632c3..3eb50b9b 100644
--- a/public/index.html
+++ b/public/index.html
@@ -86,7 +86,7 @@
 
   <!-- Value Proposition -->
   <section class="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-16" aria-labelledby="core-insight">
-    <div class="bg-amber-50 border-l-4 border-amber-500 p-6 rounded-r-lg">
+    <div class="bg-amber-50 border-l-4 border-amber-500 p-6 rounded-r-lg animate-on-scroll" data-animation="slide-up">
       <h2 id="core-insight" class="text-2xl font-bold text-amber-900 mb-3" data-i18n="value_prop.heading">A Starting Point</h2>
       <p class="text-amber-800 text-lg" data-i18n-html="value_prop.text">
         Instead of hoping AI systems <em>"behave correctly,"</em> we propose <strong>structural constraints</strong>
@@ -106,7 +106,7 @@ We recognize this is one small step in addressing AI safety challenges. Explore
     <div class="grid grid-cols-1 md:grid-cols-3 gap-8">
 
       <!-- Researcher Path → CrossReferenceValidator (Purple) -->
-      <a href="/researcher.html" class="block bg-white rounded-xl shadow-lg border-l-4 overflow-visible hover:shadow-2xl transition-all duration-300 hover:-translate-y-1 relative group animate-fade-in-scale animate-delay-100" class="border-l-service-validator">
+      <a href="/researcher.html" class="block bg-white rounded-xl shadow-lg border-l-4 overflow-visible hover:shadow-2xl transition-all duration-300 hover:-translate-y-1 relative group animate-on-scroll border-l-service-validator" data-animation="scale-in" data-stagger="100">
         <!-- Tooltip -->
         <div class="absolute bottom-full mb-4 left-1/2 transform -translate-x-1/2 bg-gray-900 text-white text-sm rounded-lg px-4 py-2 opacity-0 group-hover:opacity-100 transition-opacity duration-200 pointer-events-none z-10 w-64 text-center shadow-xl">
           <span data-i18n="paths.researcher.tooltip">For AI safety researchers, academics, and scientists investigating LLM failure modes and governance architectures</span>
@@ -154,7 +154,7 @@ Explore the theoretical foundations, architectural constraints, and scholarly co
       </a>
 
       <!-- Implementer Path → InstructionPersistenceClassifier (Indigo) -->
-      <a href="/implementer.html" class="block bg-white rounded-xl shadow-lg border-l-4 overflow-visible hover:shadow-2xl transition-all duration-300 hover:-translate-y-1 relative group animate-fade-in-scale animate-delay-200" class="border-l-service-instruction">
+      <a href="/implementer.html" class="block bg-white rounded-xl shadow-lg border-l-4 overflow-visible hover:shadow-2xl transition-all duration-300 hover:-translate-y-1 relative group animate-on-scroll border-l-service-instruction" data-animation="scale-in" data-stagger="200">
         <!-- Tooltip -->
         <div class="absolute bottom-full mb-4 left-1/2 transform -translate-x-1/2 bg-gray-900 text-white text-sm rounded-lg px-4 py-2 opacity-0 group-hover:opacity-100 transition-opacity duration-200 pointer-events-none z-10 w-64 text-center shadow-xl">
           <span data-i18n="paths.implementer.tooltip">For software engineers, ML engineers, and technical teams building production AI systems</span>
@@ -202,7 +202,7 @@ Get hands-on with implementation guides, API documentation, and reference code e
       </a>
 
       <!-- Leader Path → PluralisticDeliberationOrchestrator (Teal) -->
-      <a href="/leader.html" class="block bg-white rounded-xl shadow-lg border-l-4 overflow-visible hover:shadow-2xl transition-all duration-300 hover:-translate-y-1 relative group animate-fade-in-scale animate-delay-300" class="border-l-service-deliberation">
+      <a href="/leader.html" class="block bg-white rounded-xl shadow-lg border-l-4 overflow-visible hover:shadow-2xl transition-all duration-300 hover:-translate-y-1 relative group animate-on-scroll border-l-service-deliberation" data-animation="scale-in" data-stagger="300">
         <!-- Tooltip -->
         <div class="absolute bottom-full mb-4 left-1/2 transform -translate-x-1/2 bg-gray-900 text-white text-sm rounded-lg px-4 py-2 opacity-0 group-hover:opacity-100 transition-opacity duration-200 pointer-events-none z-10 w-64 text-center shadow-xl">
           <span data-i18n="paths.leader.tooltip">For AI executives, research directors, startup founders, and strategic decision makers setting AI safety policy</span>
@@ -257,11 +257,11 @@ Navigate the business case, compliance requirements, and competitive advantages
   <!-- Key Capabilities -->
   <section class="bg-white py-16">
     <div class="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8">
-      <h2 class="text-3xl font-bold text-center text-gray-900 mb-12" data-i18n="capabilities.heading">Framework Capabilities</h2>
+      <h2 class="text-3xl font-bold text-center text-gray-900 mb-12 animate-on-scroll" data-i18n="capabilities.heading" data-animation="fade-in">Framework Capabilities</h2>
 
       <div class="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-8">
 
-        <div class="card-base card-interactive card-service instruction">
+        <div class="card-base card-interactive card-service instruction animate-on-scroll" data-animation="slide-up" data-stagger="100">
           <div class="w-14 h-14 rounded-xl flex items-center justify-center mb-4" class="bg-gradient-service-instruction">
             <svg aria-hidden="true" class="w-7 h-7 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
               <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5H7a2 2 0 00-2 2v12a2 2 0 002 2h10a2 2 0 002-2V7a2 2 0 00-2-2h-2M9 5a2 2 0 002 2h2a2 2 0 002-2M9 5a2 2 0 012-2h2a2 2 0 012 2"/>
@@ -273,7 +273,7 @@ Quadrant-based classification (STR/OPS/TAC/SYS/STO) with time-persistence metada
           </p>
         </div>
 
-        <div class="card-base card-interactive card-service validator">
+        <div class="card-base card-interactive card-service validator animate-on-scroll" data-animation="slide-up" data-stagger="200">
           <div class="w-14 h-14 rounded-xl flex items-center justify-center mb-4" class="bg-gradient-service-validator">
             <svg aria-hidden="true" class="w-7 h-7 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
               <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 12l2 2 4-4m6 2a9 9 0 11-18 0 9 9 0 0118 0z"/>
@@ -285,7 +285,7 @@ Validates AI actions against explicit user instructions to prevent pattern-based
           </p>
         </div>
 
-        <div class="card-base card-interactive card-service boundary">
+        <div class="card-base card-interactive card-service boundary animate-on-scroll" data-animation="slide-up" data-stagger="300">
           <div class="w-14 h-14 rounded-xl flex items-center justify-center mb-4" class="bg-gradient-service-boundary">
             <svg aria-hidden="true" class="w-7 h-7 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
               <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 15v2m-6 4h12a2 2 0 002-2v-6a2 2 0 00-2-2H6a2 2 0 00-2 2v6a2 2 0 002 2zm10-10V7a4 4 0 00-8 0v4h8z"/>
@@ -297,7 +297,7 @@ Implements Tractatus 12.1-12.7 boundaries - values decisions architecturally req
           </p>
         </div>
 
-        <div class="card-base card-interactive card-service pressure">
+        <div class="card-base card-interactive card-service pressure animate-on-scroll" data-animation="slide-up" data-stagger="400">
           <div class="w-14 h-14 rounded-xl flex items-center justify-center mb-4" class="bg-gradient-service-pressure">
             <svg aria-hidden="true" class="w-7 h-7 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
               <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M13 10V3L4 14h7v7l9-11h-7z"/>
@@ -309,7 +309,7 @@ Detects degraded operating conditions (token pressure, errors, complexity) and a
           </p>
         </div>
 
-        <div class="card-base card-interactive card-service metacognitive">
+        <div class="card-base card-interactive card-service metacognitive animate-on-scroll" data-animation="slide-up" data-stagger="500">
           <div class="w-14 h-14 rounded-xl flex items-center justify-center mb-4" class="bg-gradient-service-metacognitive">
             <svg aria-hidden="true" class="w-7 h-7 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
               <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9.663 17h4.673M12 3v1m6.364 1.636l-.707.707M21 12h-1M4 12H3m3.343-5.657l-.707-.707m2.828 9.9a5 5 0 117.072 0l-.548.547A3.374 3.374 0 0014 18.469V19a2 2 0 11-4 0v-.531c0-.895-.356-1.754-.988-2.386l-.548-.547z"/>
@@ -321,7 +321,7 @@ AI self-checks alignment, coherence, safety before execution - structural pause-
           </p>
         </div>
 
-        <div class="card-base card-interactive card-service deliberation">
+        <div class="card-base card-interactive card-service deliberation animate-on-scroll" data-animation="slide-up" data-stagger="600">
           <div class="w-14 h-14 rounded-xl flex items-center justify-center mb-4" class="bg-gradient-service-deliberation">
             <svg aria-hidden="true" class="w-7 h-7 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
               <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M17 20h5v-2a3 3 0 00-5.356-1.857M17 20H7m10 0v-2c0-.656-.126-1.283-.356-1.857M7 20H2v-2a3 3 0 015.356-1.857M7 20v-2c0-.656.126-1.283.356-1.857m0 0a5.002 5.002 0 019.288 0M15 7a3 3 0 11-6 0 3 3 0 016 0zm6 3a2 2 0 11-4 0 2 2 0 014 0zM7 10a2 2 0 11-4 0 2 2 0 014 0z"/>
@@ -395,6 +395,9 @@ Additional case studies and research findings documented in technical papers
   <script src="/js/i18n-simple.js?v=1760818106"></script>
   <script src="/js/components/language-selector.js?v=1760818106"></script>
 
+  <!-- Scroll Animations (Phase 3) -->
+  <script src="/js/scroll-animations.js"></script>
+
   <!-- Footer Component -->
   <script src="/js/components/footer.js"></script>
 
diff --git a/public/js/scroll-animations.js b/public/js/scroll-animations.js
new file mode 100644
index 00000000..d6839575
--- /dev/null
+++ b/public/js/scroll-animations.js
@@ -0,0 +1,135 @@
+/**
+ * Scroll Animations using Intersection Observer
+ * Tractatus Framework - Phase 3: Engagement & Interactive Features
+ *
+ * Provides smooth scroll-triggered animations for elements marked with .animate-on-scroll
+ * Supports multiple animation types via data-animation attribute
+ */
+
+class ScrollAnimations {
+  constructor(options = {}) {
+    this.observerOptions = {
+      threshold: options.threshold || 0.1,
+      rootMargin: options.rootMargin || '0px 0px -100px 0px'
+    };
+
+    this.animations = {
+      'fade-in': 'opacity-0 animate-fade-in',
+      'slide-up': 'opacity-0 translate-y-8 animate-slide-up',
+      'slide-down': 'opacity-0 -translate-y-8 animate-slide-down',
+      'slide-left': 'opacity-0 translate-x-8 animate-slide-left',
+      'slide-right': 'opacity-0 -translate-x-8 animate-slide-right',
+      'scale-in': 'opacity-0 scale-95 animate-scale-in',
+      'rotate-in': 'opacity-0 rotate-12 animate-rotate-in'
+    };
+
+    this.init();
+  }
+
+  init() {
+    // Wait for DOM to be ready
+    if (document.readyState === 'loading') {
+      document.addEventListener('DOMContentLoaded', () => this.observe());
+    } else {
+      this.observe();
+    }
+
+    console.log('[ScrollAnimations] Initialized');
+  }
+
+  observe() {
+    const observer = new IntersectionObserver((entries) => {
+      entries.forEach(entry => {
+        if (entry.isIntersecting) {
+          this.animateElement(entry.target);
+
+          // Optional: unobserve after animation to improve performance
+          // Only do this for elements without data-animate-repeat attribute
+          if (!entry.target.hasAttribute('data-animate-repeat')) {
+            observer.unobserve(entry.target);
+          }
+        } else if (entry.target.hasAttribute('data-animate-repeat')) {
+          // Reset animation for repeatable elements
+          this.resetElement(entry.target);
+        }
+      });
+    }, this.observerOptions);
+
+    // Find all elements with .animate-on-scroll class
+    const elements = document.querySelectorAll('.animate-on-scroll');
+    console.log(`[ScrollAnimations] Observing ${elements.length} elements`);
+
+    elements.forEach((el, index) => {
+      // Add stagger delay if data-stagger attribute is present
+      if (el.hasAttribute('data-stagger')) {
+        const delay = parseInt(el.getAttribute('data-stagger')) || (index * 100);
+        el.style.animationDelay = `${delay}ms`;
+      }
+
+      // Apply initial animation classes based on data-animation attribute
+      const animationType = el.getAttribute('data-animation') || 'fade-in';
+      if (this.animations[animationType]) {
+        // Remove any existing animation classes
+        Object.values(this.animations).forEach(classes => {
+          classes.split(' ').forEach(cls => el.classList.remove(cls));
+        });
+
+        // Add initial state classes (will be removed when visible)
+        const initialClasses = this.getInitialClasses(animationType);
+        initialClasses.forEach(cls => el.classList.add(cls));
+      }
+
+      observer.observe(el);
+    });
+  }
+
+  getInitialClasses(animationType) {
+    // Return classes that represent the "before animation" state
+    const map = {
+      'fade-in': ['opacity-0'],
+      'slide-up': ['opacity-0', 'translate-y-8'],
+      'slide-down': ['opacity-0', '-translate-y-8'],
+      'slide-left': ['opacity-0', 'translate-x-8'],
+      'slide-right': ['opacity-0', '-translate-x-8'],
+      'scale-in': ['opacity-0', 'scale-95'],
+      'rotate-in': ['opacity-0', 'rotate-12']
+    };
+
+    return map[animationType] || ['opacity-0'];
+  }
+
+  animateElement(element) {
+    // Remove initial state classes
+    element.classList.remove('opacity-0', 'translate-y-8', '-translate-y-8', 'translate-x-8', '-translate-x-8', 'scale-95', 'rotate-12');
+
+    // Add visible state
+    element.classList.add('is-visible');
+
+    // Trigger custom event for other components to listen to
+    element.dispatchEvent(new CustomEvent('scroll-animated', {
+      bubbles: true,
+      detail: { element }
+    }));
+  }
+
+  resetElement(element) {
+    // Remove visible state
+    element.classList.remove('is-visible');
+
+    // Re-apply initial animation classes
+    const animationType = element.getAttribute('data-animation') || 'fade-in';
+    const initialClasses = this.getInitialClasses(animationType);
+    initialClasses.forEach(cls => element.classList.add(cls));
+  }
+}
+
+// Auto-initialize when script loads
+// Can be disabled by setting window.DISABLE_AUTO_SCROLL_ANIMATIONS = true before loading this script
+if (typeof window !== 'undefined' && !window.DISABLE_AUTO_SCROLL_ANIMATIONS) {
+  window.scrollAnimations = new ScrollAnimations();
+}
+
+// Export for module usage
+if (typeof module !== 'undefined' && module.exports) {
+  module.exports = ScrollAnimations;
+}