:root {
    --primary: #0f766e;
    --primary-dark: #0d9488;
    --accent: #14b8a6;
    --dark: #134e4a;
    --light: #f0fdfa;
    --gray-100: #f5f5f5;
    --gray-200: #e5e5e5;
    --gray-600: #666666;
    --gray-800: #333333;
    --gradient: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.8;
    color: var(--gray-800);
    background: #ffffff;
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 2rem;
}

/* Navigation */
nav {
    background: #ffffff;
    border-bottom: 3px solid var(--primary);
    padding: 1.5rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05);
}

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

nav h1 a {
    color: var(--dark);
    text-decoration: none;
    font-size: 1.6rem;
    font-weight: 700;
    letter-spacing: -0.5px;
}

#menu {
    display: flex;
    list-style: none;
    gap: 2.5rem;
}

#menu li a {
    color: var(--gray-600);
    text-decoration: none;
    font-weight: 600;
    font-size: 0.95rem;
    transition: all 0.3s;
    padding: 0.5rem 0;
    position: relative;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

#menu li a:hover,
#menu li a.active {
    color: var(--primary);
}

#menu li a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary);
    transition: width 0.3s;
}

#menu li a:hover::after,
#menu li a.active::after {
    width: 100%;
}

/* Mobile Menu */
.menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--dark);
}

/* Hero Section */
.hero {
    background: var(--light);
    padding: 70px 0;
    text-align: center;
    border-bottom: 1px solid var(--gray-200);
}

.hero h1 {
    font-size: 2.8rem;
    color: var(--dark);
    margin-bottom: 1rem;
    font-weight: 700;
    letter-spacing: -1px;
}

.hero p {
    font-size: 1.15rem;
    color: var(--gray-600);
    max-width: 750px;
    margin: 0 auto;
}

/* Breadcrumb */
.breadcrumb {
    background: #ffffff;
    padding: 1rem 0;
    border-bottom: 1px solid var(--gray-200);
}

.breadcrumb ul {
    list-style: none;
    display: flex;
    gap: 0.5rem;
    font-size: 0.9rem;
}

.breadcrumb li::after {
    content: '›';
    margin-left: 0.5rem;
    color: var(--gray-600);
}

.breadcrumb li:last-child::after {
    display: none;
}

.breadcrumb li a {
    color: var(--primary);
    text-decoration: none;
}

.breadcrumb li:last-child a {
    color: var(--gray-600);
}

/* Content Sections */
section {
    padding: 70px 0;
}

section:nth-child(even) {
    background: var(--light);
}

h2 {
    font-size: 2.2rem;
    color: var(--dark);
    margin-bottom: 2rem;
    line-height: 1.3;
    font-weight: 700;
    border-bottom: 3px solid var(--primary);
    padding-bottom: 0.75rem;
    display: inline-block;
}

h3 {
    font-size: 1.4rem;
    color: var(--dark);
    margin: 2rem 0 1rem;
    font-weight: 600;
}

p {
    margin-bottom: 1rem;
    color: var(--gray-600);
}

/* Encyclopedia Cards */
.encyclopedia-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 2rem;
    margin-top: 2.5rem;
}

.encyclopedia-card {
    background: white;
    padding: 2.5rem;
    border-radius: 4px;
    border: 1px solid var(--gray-200);
    transition: all 0.3s;
    position: relative;
}

.encyclopedia-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: var(--primary);
    transform: scaleY(0);
    transition: transform 0.3s;
}

.encyclopedia-card:hover::before {
    transform: scaleY(1);
}

.encyclopedia-card:hover {
    box-shadow: 0 8px 24px rgba(15, 118, 110, 0.12);
    transform: translateY(-4px);
}

.encyclopedia-card h3 {
    color: var(--primary);
    margin-bottom: 1rem;
    font-size: 1.3rem;
}

.encyclopedia-card p {
    font-size: 0.95rem;
    line-height: 1.8;
}

.encyclopedia-card ul {
    list-style: none;
    margin-top: 1rem;
}

.encyclopedia-card ul li {
    padding: 0.6rem 0;
    color: var(--gray-600);
    position: relative;
    padding-left: 1.5rem;
    font-size: 0.95rem;
    border-bottom: 1px solid var(--gray-100);
}

.encyclopedia-card ul li:last-child {
    border-bottom: none;
}

.encyclopedia-card ul li::before {
    content: '▸';
    position: absolute;
    left: 0;
    color: var(--primary);
    font-weight: bold;
}

/* Info Boxes */
.info-box {
    background: white;
    padding: 2rem;
    margin: 2rem 0;
    border-left: 4px solid var(--primary);
    border-radius: 0 4px 4px 0;
}

.info-box h4 {
    color: var(--primary);
    margin-bottom: 1rem;
    font-size: 1.1rem;
}

/* Table of Contents */
.toc {
    background: white;
    padding: 2rem;
    margin: 2rem 0;
    border: 1px solid var(--gray-200);
    border-radius: 4px;
}

.toc h3 {
    color: var(--dark);
    margin-bottom: 1rem;
    font-size: 1.2rem;
}

.toc ol {
    margin: 1rem 0;
    padding-left: 2rem;
}

.toc li {
    margin-bottom: 0.75rem;
}

.toc a {
    color: var(--primary);
    text-decoration: none;
    transition: opacity 0.3s;
}

.toc a:hover {
    opacity: 0.7;
}

/* Contact Form */
.contact-form {
    max-width: 700px;
    margin: 2rem 0;
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    color: var(--dark);
    font-weight: 600;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 12px 16px;
    border: 1px solid var(--gray-200);
    border-radius: 4px;
    font-size: 1rem;
    font-family: inherit;
    transition: border-color 0.3s;
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary);
}

.form-group textarea {
    resize: vertical;
    min-height: 150px;
}

.btn {
    display: inline-block;
    padding: 12px 32px;
    background: var(--primary);
    color: white;
    text-decoration: none;
    border-radius: 4px;
    font-weight: 600;
    transition: all 0.3s;
    border: 2px solid var(--primary);
    cursor: pointer;
}

.btn:hover {
    background: var(--primary-dark);
    border-color: var(--primary-dark);
}

.btn-outline {
    background: transparent;
    color: var(--primary);
    margin-left: 1rem;
}

.btn-outline:hover {
    background: var(--primary);
    color: white;
}

/* Footer */
footer {
    background: var(--dark);
    color: white;
    padding: 40px 0;
    text-align: center;
}

footer p {
    opacity: 0.8;
    color: rgba(255, 255, 255, 0.8);
}

/* Responsive */
@media (max-width: 768px) {
    #menu {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: white;
        flex-direction: column;
        padding: 1rem 2rem;
        gap: 0;
        border-bottom: 3px solid var(--primary);
    }

    #menu.active {
        display: flex;
    }

    #menu li {
        border-bottom: 1px solid var(--gray-200);
    }

    #menu li a {
        display: block;
        padding: 1rem 0;
    }

    .menu-toggle {
        display: block;
    }

    .hero h1 {
        font-size: 2rem;
    }

    h2 {
        font-size: 1.8rem;
    }

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

    .btn-outline {
        margin-left: 0;
        margin-top: 1rem;
    }
}

@media (max-width: 968px) {
    .container {
        padding: 0 1.5rem;
    }
}