/* ==========================================
   Probability Learning Portal - Styles
   Academic Design
   ========================================== */

/* CSS Variables - Academic Color Palette */
:root {
    --primary-navy: #1a365d;
    --primary-blue: #2c5282;
    --accent-blue: #3182ce;
    --text-dark: #2d3748;
    --text-medium: #4a5568;
    --text-light: #718096;
    --bg-white: #ffffff;
    --bg-grey-lightest: #f7fafc;
    --bg-grey-light: #edf2f7;
    --border-grey: #e2e8f0;
    --border-dark: #cbd5e0;
    --success-green: #38a169;
    --highlight-yellow: #fef5e7;

    /* Typography */
    --font-serif: 'Crimson Text', Georgia, serif;
    --font-sans: 'Inter', -apple-system, sans-serif;

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;

    /* Transitions */
    --transition-base: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: var(--font-sans);
    color: var(--text-dark);
    background-color: var(--bg-grey-lightest);
    line-height: 1.7;
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
}

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-lg);
}

/* ==========================================
   Header
   ========================================== */
.header {
    text-align: center;
    padding: var(--spacing-xl) 0;
    margin-bottom: var(--spacing-lg);
    position: relative;
}

.header::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 100px;
    height: 3px;
    background: linear-gradient(90deg, transparent, var(--accent-blue), transparent);
    animation: expandLine 1.5s ease-out;
}

@keyframes expandLine {
    from {
        width: 0;
        opacity: 0;
    }

    to {
        width: 100px;
        opacity: 1;
    }
}

.portal-title {
    font-family: var(--font-serif);
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-navy);
    margin-bottom: var(--spacing-xs);
    animation: fadeInDown 0.6s ease-out;
}

.course-code {
    font-size: 1.1rem;
    color: var(--text-medium);
    font-weight: 500;
    letter-spacing: 0.5px;
    margin-bottom: var(--spacing-xs);
    animation: fadeInDown 0.8s ease-out;
}

.tagline {
    font-size: 1rem;
    color: var(--text-light);
    font-style: italic;
    animation: fadeInDown 1s ease-out;
}

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ==========================================
   Introduction Section
   ========================================== */
.intro-section {
    margin-bottom: var(--spacing-xl);
}

.intro-card {
    background: var(--bg-white);
    border: 1px solid var(--border-grey);
    border-radius: 8px;
    padding: var(--spacing-lg);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
    transition: all var(--transition-base);
    animation: fadeInUp 0.8s ease-out;
}

.intro-card:hover {
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.08);
    transform: translateY(-2px);
}

.intro-card h2 {
    font-family: var(--font-serif);
    font-size: 1.75rem;
    color: var(--primary-navy);
    margin-bottom: var(--spacing-md);
}

.intro-card>p {
    color: var(--text-medium);
    margin-bottom: var(--spacing-lg);
    line-height: 1.8;
}

/* Learning Methodology */
.learning-approach {
    margin-top: var(--spacing-lg);
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--border-grey);
}

.learning-approach h3 {
    font-family: var(--font-sans);
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-dark);
    margin-bottom: var(--spacing-md);
}

.methodology-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-sm);
}

.method-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm);
    background: var(--bg-grey-lightest);
    border-radius: 6px;
    transition: all var(--transition-base);
    cursor: default;
}

.method-item:hover {
    background: var(--highlight-yellow);
    transform: translateX(4px);
}

.method-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    background: var(--primary-navy);
    color: white;
    border-radius: 50%;
    font-size: 0.875rem;
    font-weight: 600;
    flex-shrink: 0;
}

.method-label {
    font-size: 0.9rem;
    color: var(--text-medium);
    font-weight: 500;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ==========================================
   Tutorial Sheets Section
   ========================================== */
.tutorials-section {
    margin-bottom: var(--spacing-xl);
}

.section-title {
    font-family: var(--font-serif);
    font-size: 2rem;
    color: var(--primary-navy);
    margin-bottom: var(--spacing-lg);
    text-align: center;
}

.tutorials-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: var(--spacing-lg);
}

/* Tutorial Card */
.tutorial-card {
    background: var(--bg-white);
    border: 2px solid var(--border-grey);
    border-radius: 8px;
    padding: var(--spacing-lg);
    text-decoration: none;
    color: inherit;
    display: block;
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
    animation: fadeInUp 0.6s ease-out backwards;
}

.tutorial-card:nth-child(1) {
    animation-delay: 0.1s;
}

.tutorial-card:nth-child(2) {
    animation-delay: 0.2s;
}

.tutorial-card:nth-child(3) {
    animation-delay: 0.3s;
}

.tutorial-card:nth-child(4) {
    animation-delay: 0.4s;
}

.tutorial-card:nth-child(5) {
    animation-delay: 0.5s;
}

.tutorial-card:nth-child(6) {
    animation-delay: 0.6s;
}

.tutorial-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(49, 130, 206, 0.05), transparent);
    transition: left 0.6s ease;
}

.tutorial-card:hover::before {
    left: 100%;
}

.tutorial-card.active {
    border-color: var(--accent-blue);
}

.tutorial-card.active:hover {
    box-shadow: 0 8px 24px rgba(49, 130, 206, 0.15);
    transform: translateY(-4px);
}

.tutorial-card.disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

.tutorial-card.disabled:hover {
    transform: none;
}

/* Tutorial Header */
.tutorial-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-md);
}

.tutorial-number {
    font-family: var(--font-serif);
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-navy);
    opacity: 0.15;
    line-height: 1;
}

.status-badge {
    padding: 4px 12px;
    border-radius: 12px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    background: var(--success-green);
    color: white;
}

.status-badge.coming-soon {
    background: var(--text-light);
}

/* Tutorial Content */
.tutorial-card h3 {
    font-family: var(--font-serif);
    font-size: 1.4rem;
    color: var(--primary-navy);
    margin-bottom: var(--spacing-sm);
    line-height: 1.3;
}

.tutorial-desc {
    color: var(--text-medium);
    font-size: 0.95rem;
    line-height: 1.6;
    margin-bottom: var(--spacing-md);
}

.tutorial-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: var(--spacing-sm);
    border-top: 1px solid var(--border-grey);
}

.question-count {
    font-size: 0.875rem;
    color: var(--text-light);
    font-weight: 500;
}

.arrow {
    font-size: 1.5rem;
    color: var(--accent-blue);
    transition: transform var(--transition-base);
}

.tutorial-card.active:hover .arrow {
    transform: translateX(6px);
}

/* ==========================================
   Footer
   ========================================== */
.footer {
    text-align: center;
    padding: var(--spacing-xl) 0;
    border-top: 1px solid var(--border-grey);
    margin-top: var(--spacing-xl);
    color: var(--text-light);
}

.footer p {
    margin-bottom: var(--spacing-xs);
    font-size: 0.9rem;
}

.footer-note {
    font-style: italic;
    font-size: 0.875rem;
}

/* ==========================================
   Responsive Design
   ========================================== */
@media (max-width: 768px) {
    .container {
        padding: var(--spacing-md);
    }

    .portal-title {
        font-size: 2rem;
    }

    .tutorials-grid {
        grid-template-columns: 1fr;
    }

    .methodology-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 480px) {
    .portal-title {
        font-size: 1.75rem;
    }

    .methodology-grid {
        grid-template-columns: 1fr;
    }
}