/* EduTwin Design System */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600&family=Merriweather:ital,wght@0,300;0,400;0,700;1,300&display=swap');

html {
    scroll-behavior: smooth;
}

:root {
    /* Colors */
    --color-bg-primary: #F8F9FA;
    --color-bg-secondary: #FFFFFF;
    --color-text-primary: #1A1A1A;
    --color-text-secondary: #4A4A4A;
    --color-brand-blue: #003366;
    --color-brand-green: #8FA69B;
    --color-brand-blue-light: #E6F0F9;
    --color-accent: #2D6A4F;

    /* Typography */
    --font-primary: 'Inter', sans-serif;
    --font-heading: 'Merriweather', serif;

    /* Spacing */
    --space-xs: 0.5rem;
    /* 8px */
    --space-sm: 1rem;
    /* 16px */
    --space-md: 2rem;
    /* 32px */
    --space-lg: 4rem;
    /* 64px */
    --space-xl: 8rem;
    /* 128px */

    /* Layout */
    --container-width: 1200px;
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 16px;

    /* Shadows */
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 12px 24px rgba(0, 0, 0, 0.12);
}

/* Reset & Base */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    background-color: var(--color-bg-primary);
    color: var(--color-text-primary);
    font-family: var(--font-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

h1,
h2,
h3,
h4,
h5,
h6 {
    font-family: var(--font-heading);
    color: var(--color-brand-blue);
    line-height: 1.2;
    margin-bottom: var(--space-show);
}

a {
    color: var(--color-brand-blue);
    text-decoration: none;
    transition: opacity 0.2s ease;
}

a:hover {
    opacity: 0.8;
}

img {
    max-width: 100%;
    display: block;
}

/* Utilities */
.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 var(--space-sm);
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 24px;
    border-radius: var(--radius-sm);
    font-weight: 500;
    transition: all 0.2s ease;
    cursor: pointer;
    font-family: var(--font-primary);
}

.btn-primary {
    background-color: var(--color-brand-blue);
    color: white;
}

.btn-primary:hover {
    background-color: #002244;
    transform: translateY(-1px);
}

.btn-secondary {
    background-color: transparent;
    border: 1px solid var(--color-brand-blue);
    color: var(--color-brand-blue);
}

.btn-secondary:hover {
    background-color: var(--color-brand-blue-light);
}

.section {
    padding: var(--space-xl) 0;
}

/* Navigation */
.main-header {
    padding: 20px 0;
    position: sticky;
    top: 0;
    background-color: rgba(248, 249, 250, 0.95);
    backdrop-filter: blur(10px);
    z-index: 1000;
    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
}

.main-header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-family: var(--font-heading);
    font-weight: 700;
    font-size: 1.5rem;
    color: var(--color-brand-blue);
    letter-spacing: -0.02em;
}

.nav-links {
    display: flex;
    gap: 2rem;
    list-style: none;
}

.nav-links a {
    color: var(--color-text-secondary);
    font-size: 0.95rem;
    font-weight: 500;
}

.nav-links a:hover {
    color: var(--color-brand-blue);
}

/* Hero Section */
.hero-section {
    padding: 6rem 0 8rem;
    background: radial-gradient(circle at top right, rgba(143, 166, 155, 0.15), transparent 60%),
        radial-gradient(circle at bottom left, rgba(0, 51, 102, 0.05), transparent 60%);
    overflow: hidden;
}

.hero-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
}

.hero-content {
    max-width: 600px;
}

.hero-label {
    display: inline-block;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-brand-green);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 1rem;
}

.hero-title {
    font-size: 3.5rem;
    margin-bottom: 1.5rem;
    color: var(--color-brand-blue);
    line-height: 1.1;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--color-text-secondary);
    margin-bottom: 2.5rem;
    max-width: 90%;
}

.hero-actions {
    display: flex;
    gap: 1rem;
}

/* Hero Visual (Abstract) */
.hero-visual {
    position: relative;
    height: 400px;
    display: flex;
    justify-content: center;
    align-items: center;
}

.abstract-shape {
    position: relative;
    width: 300px;
    height: 300px;
}

.shape-circle {
    position: absolute;
    width: 100%;
    height: 100%;
    border-radius: 50%;
    border: 1px solid var(--color-brand-blue);
    opacity: 0.2;
    animation: pulse 4s infinite ease-in-out;
}

.shape-line {
    position: absolute;
    top: 50%;
    left: 0;
    width: 100%;
    height: 1px;
    background: linear-gradient(90deg, transparent, var(--color-brand-green), transparent);
    transform: rotate(45deg);
}

.shape-dot {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 12px;
    height: 12px;
    background: var(--color-brand-blue);
    border-radius: 50%;
    transform: translate(-50%, -50%);
    box-shadow: 0 0 20px rgba(0, 51, 102, 0.4);
}

@keyframes pulse {
    0% {
        transform: scale(0.95);
        opacity: 0.1;
    }

    50% {
        transform: scale(1.05);
        opacity: 0.3;
    }

    100% {
        transform: scale(0.95);
        opacity: 0.1;
    }
}

/* Responsive */
@media (max-width: 768px) {
    .hero-container {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .hero-actions {
        justify-content: center;
    }

    .hero-title {
        font-size: 2.5rem;
    }
}

/* Section Headers */
.section-header {
    text-align: center;
    max-width: 700px;
    margin: 0 auto 4rem;
}

.section-header h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.section-subtitle {
    font-size: 1.125rem;
    color: var(--color-text-secondary);
}

.label-accent {
    display: inline-block;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-brand-blue);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 1rem;
    background-color: var(--color-brand-blue-light);
    padding: 4px 12px;
    border-radius: 100px;
}

/* Problem Section */
.problem-section {
    background-color: var(--color-bg-secondary);
}

.problem-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
}

.problem-card {
    background: var(--color-bg-primary);
    padding: 2.5rem;
    border-radius: var(--radius-lg);
    border: 1px solid rgba(0, 0, 0, 0.05);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.problem-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}

.card-icon {
    font-size: 2rem;
    margin-bottom: 1.5rem;
}

.problem-card h3 {
    font-size: 1.25rem;
    margin-bottom: 1rem;
    color: var(--color-text-primary);
}

.problem-card p {
    color: var(--color-text-secondary);
    font-size: 0.95rem;
}

/* Concept Section */
.concept-layout {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 5rem;
    align-items: center;
}

.concept-text h2 {
    font-size: 2.5rem;
    margin-bottom: 1.5rem;
}

.concept-text p {
    font-size: 1.125rem;
    color: var(--color-text-secondary);
    margin-bottom: 2rem;
}

.concept-list {
    list-style: none;
}

.concept-list li {
    margin-bottom: 1rem;
    padding-left: 1.5rem;
    position: relative;
    color: var(--color-text-secondary);
}

.concept-list li::before {
    content: "•";
    color: var(--color-brand-green);
    position: absolute;
    left: 0;
    font-weight: bold;
}

.concept-list strong {
    color: var(--color-brand-blue);
}

/* Concept Visualization */
.twin-graphic {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    position: relative;
    padding: 2rem;
    background: var(--color-bg-secondary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
}

.student-node,
.ai-node,
.twin-node {
    padding: 1rem 2rem;
    background: white;
    border: 1px solid var(--color-brand-blue-light);
    border-radius: var(--radius-md);
    font-weight: 600;
    color: var(--color-brand-blue);
    width: 200px;
    text-align: center;
    z-index: 2;
}

.twin-node {
    background: var(--color-brand-blue);
    color: white;
    box-shadow: 0 0 15px rgba(0, 51, 102, 0.2);
}

.process-line {
    width: 2px;
    height: 30px;
    background: var(--color-brand-green);
    position: relative;
}

.process-line::after {
    content: "";
    /* Arrow head */
    position: absolute;
    bottom: 0;
    left: -4px;
    border-left: 5px solid transparent;
    border-right: 5px solid transparent;
    border-top: 5px solid var(--color-brand-green);
}

/* Responsive */
@media (max-width: 900px) {

    .problem-grid,
    .concept-layout {
        grid-template-columns: 1fr;
    }
}

/* Capabilities Section */
.capabilities-section {
    background-color: var(--color-bg-primary);
}

.capabilities-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 3rem;
    max-width: 1000px;
    margin: 0 auto;
}

.capability-item {
    padding: 2rem;
    border-left: 2px solid var(--color-brand-blue-light);
    transition: all 0.3s ease;
}

.capability-item:hover {
    border-left-color: var(--color-brand-blue);
    background-color: white;
    box-shadow: var(--shadow-sm);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.cap-number {
    font-family: var(--font-heading);
    font-size: 3rem;
    color: rgba(0, 51, 102, 0.1);
    font-weight: 700;
    line-height: 1;
    margin-bottom: 1rem;
}

.capability-item:hover .cap-number {
    color: rgba(0, 51, 102, 0.2);
}

.capability-item h3 {
    font-size: 1.5rem;
    margin-bottom: 0.75rem;
}

.capability-item p {
    color: var(--color-text-secondary);
}

/* Responsive Capabilities */
@media (max-width: 768px) {
    .capabilities-grid {
        grid-template-columns: 1fr;
        gap: 2rem;
    }
}

/* Ethics Section */
.ethics-section {
    background-color: var(--color-bg-secondary);
}

.ethics-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
}

.ethics-card {
    text-align: center;
    padding: 2rem;
}

.ethics-card h3 {
    font-size: 1.25rem;
    margin-bottom: 1rem;
    color: var(--color-brand-blue);
}

.ethics-card p {
    color: var(--color-text-secondary);
}

/* Impact Section */
.impact-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
}

.impact-list {
    list-style: none;
    margin-top: 2rem;
}

.impact-list li {
    margin-bottom: 1.5rem;
    font-size: 1.125rem;
    display: flex;
    align-items: center;
    gap: 1rem;
}

.impact-stat {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-brand-green);
    min-width: 80px;
}

.bar-chart {
    display: flex;
    justify-content: center;
    align-items: flex-end;
    gap: 2rem;
    height: 300px;
    padding: 20px;
    border-bottom: 2px solid rgba(0, 0, 0, 0.1);
}

.bar {
    width: 60px;
    background: rgba(0, 0, 0, 0.1);
    border-radius: var(--radius-sm) var(--radius-sm) 0 0;
    position: relative;
    transition: height 1s ease;
}

.bar span {
    position: absolute;
    bottom: -30px;
    width: 100%;
    text-align: center;
    font-weight: 500;
    font-size: 0.875rem;
}

.bar.highlight {
    background: var(--color-brand-blue);
}

/* CTA Section */
.cta-section {
    text-align: center;
    padding: 8rem 0;
    background: linear-gradient(135deg, rgba(255, 255, 255, 0.5), rgba(230, 240, 249, 0.5));
}

.cta-container h2 {
    font-size: 3rem;
    margin-bottom: 1.5rem;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

.cta-container p {
    font-size: 1.25rem;
    color: var(--color-text-secondary);
    margin-bottom: 2.5rem;
}

.cta-actions {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

.btn.bg-white {
    background-color: white;
}

/* Responsive Final */
@media (max-width: 768px) {

    .ethics-grid,
    .impact-content {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .impact-list li {
        flex-direction: column;
        gap: 0.5rem;
    }

    .cta-container h2 {
        font-size: 2rem;
    }

    .cta-actions {
        flex-direction: column;
    }
}

/* Footer */
.main-footer {
    padding: 2rem 0;
    background-color: white;
    border-top: 1px solid rgba(0, 0, 0, 0.05);
    text-align: center;
    color: var(--color-text-secondary);
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    font-size: 0.875rem;
}

/* Animations */
.reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: all 0.8s cubic-bezier(0.5, 0, 0, 1);
}

.reveal.active {
    opacity: 1;
    transform: translateY(0);
}

/* Mobile Navigation Controls */
.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    flex-direction: column;
    gap: 4px;
    padding: 0.5rem;
    z-index: 1001;
}

.bar {
    display: block;
    width: 24px;
    height: 2px;
    background-color: var(--color-text-primary);
    transition: all 0.3s ease;
}

.mobile-only {
    display: none;
}

/* Updated Responsive Styles */
@media (max-width: 768px) {
    .mobile-menu-btn {
        display: flex;
    }

    .desktop-only {
        display: none;
    }

    .nav-links {
        position: fixed;
        top: 0;
        right: -100%;
        width: 80%;
        max-width: 300px;
        height: 100vh;
        background: white;
        flex-direction: column;
        padding: 5rem 2rem;
        box-shadow: -5px 0 15px rgba(0, 0, 0, 0.1);
        transition: right 0.3s cubic-bezier(0.4, 0, 0.2, 1);
        z-index: 1000;
        gap: 1.5rem;
    }

    .nav-links.active {
        right: 0;
    }

    .nav-links a {
        font-size: 1.125rem;
        border-bottom: 1px solid rgba(0, 0, 0, 0.05);
        padding-bottom: 0.5rem;
        display: block;
    }

    .mobile-only {
        display: block;
    }

    /* Hamburger Animation */
    .mobile-menu-btn.active .bar:nth-child(1) {
        transform: translateY(6px) rotate(45deg);
    }

    .mobile-menu-btn.active .bar:nth-child(2) {
        opacity: 0;
    }

    .mobile-menu-btn.active .bar:nth-child(3) {
        transform: translateY(-6px) rotate(-45deg);
    }
}