/* ===========================
   CSS Variables & Root Styles
   =========================== */

:root {
    /* Colors */
    --color-primary: #2563eb;
    --color-primary-dark: #1e40af;
    --color-accent: #dc2626;
    --color-bg-light: #f9fafb;
    --color-bg-white: #ffffff;
    --color-text-dark: #1f2937;
    --color-text-gray: #6b7280;
    --color-border: #e5e7eb;
    --color-tag-bg: #eff6ff;
    --color-tag-text: #0c4a6e;

    /* Typography */
    --font-display: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    --font-body: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    --font-mono: 'Monaco', 'Courier New', monospace;

    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    --spacing-3xl: 4rem;

    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;

    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-normal: 300ms ease-in-out;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

/* ===========================
   Reset & Base Styles
   =========================== */

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-body);
    line-height: 1.6;
    color: var(--color-text-dark);
    background-color: var(--color-bg-white);
}

a {
    color: var(--color-primary);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--color-primary-dark);
}

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

ul {
    list-style: none;
}

/* ===========================
   Layout & Container
   =========================== */

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

/* ===========================
   Header & Navigation
   =========================== */

.header {
    background-color: var(--color-bg-white);
    border-bottom: 1px solid var(--color-border);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow-sm);
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-lg) 0;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: -0.5px;
}

.logo a {
    color: var(--color-text-dark);
}

.logo a:hover {
    color: var(--color-primary);
}

.nav-list {
    display: flex;
    gap: var(--spacing-xl);
}

.nav-link {
    font-size: 0.95rem;
    font-weight: 500;
    position: relative;
    color: var(--color-text-dark);
    transition: color var(--transition-fast);
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--color-primary);
    transition: width var(--transition-normal);
}

.nav-link:hover {
    color: var(--color-primary);
}

.nav-link:hover::after,
.nav-link.active::after {
    width: 100%;
}

/* ===========================
   Search Section (Inline)
   =========================== */

.search-container-inline {
    position: relative;
    display: flex;
    align-items: center;
}

.search-toggle-btn {
    background: none;
    border: none;
    color: var(--color-text-dark);
    cursor: pointer;
    padding: var(--spacing-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: color var(--transition-fast);
    border-radius: var(--radius-md);
}

.search-toggle-btn:hover {
    color: var(--color-primary);
    background-color: var(--color-bg-light);
}

.search-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: 999;
    display: none;
}

.search-overlay.active {
    display: block;
}

.search-wrapper-inline {
    position: absolute;
    top: 100%;
    right: 0;
    margin-top: var(--spacing-md);
    width: 400px;
    background-color: var(--color-bg-white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: opacity var(--transition-normal), visibility var(--transition-normal), transform var(--transition-normal);
    padding: var(--spacing-md);
    border: 1px solid var(--color-border);
}

.search-wrapper-inline.active {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.search-input-inline {
    width: 100%;
    padding: var(--spacing-md);
    font-size: 1rem;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    background-color: var(--color-bg-white);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.search-input-inline:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.search-input-inline::placeholder {
    color: var(--color-text-gray);
}

.search-close-btn {
    position: absolute;
    right: var(--spacing-md);
    top: var(--spacing-md);
    background: none;
    border: none;
    color: var(--color-text-gray);
    cursor: pointer;
    padding: var(--spacing-xs);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: color var(--transition-fast);
}

.search-close-btn:hover {
    color: var(--color-text-dark);
}

.search-results {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    margin-top: var(--spacing-sm);
    background-color: var(--color-bg-white);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    display: none;
    max-height: 400px;
    overflow-y: auto;
}

.search-results.active {
    display: block;
}

.search-result-item {
    padding: var(--spacing-md);
    border-bottom: 1px solid var(--color-border);
    cursor: pointer;
    transition: background-color var(--transition-fast);
    display: block;
    color: inherit;
    text-decoration: none;
}

.search-result-item:last-child {
    border-bottom: none;
}

.search-result-item:hover {
    background-color: var(--color-bg-light);
}

.search-result-title {
    font-weight: 600;
    color: var(--color-text-dark);
    margin-bottom: var(--spacing-xs);
}

.search-result-meta {
    font-size: 0.85rem;
    color: var(--color-text-gray);
}

.search-result-section {
    display: inline-block;
    background-color: var(--color-tag-bg);
    color: var(--color-tag-text);
    font-size: 0.75rem;
    font-weight: 600;
    padding: 2px 6px;
    border-radius: var(--radius-sm);
    margin-right: var(--spacing-xs);
}

.search-no-results {
    padding: var(--spacing-xl);
    text-align: center;
    color: var(--color-text-gray);
}

/* ===========================
   Hero Section
   =========================== */

.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: var(--color-bg-white);
    padding: var(--spacing-3xl) var(--spacing-lg);
    text-align: center;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
}

.hero-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    letter-spacing: -1px;
}

.hero-subtitle {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-lg);
    opacity: 0.95;
}

.hero-description {
    font-size: 1rem;
    opacity: 0.9;
    line-height: 1.8;
}

/* ===========================
   Section Header Hero
   =========================== */

.section-header-hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: var(--color-bg-white);
    padding: var(--spacing-3xl) var(--spacing-lg);
}

.section-header-hero .container {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: var(--spacing-2xl);
}

.section-header-content {
    flex: 1;
}

.section-title-hero {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    letter-spacing: -1px;
}

.section-subtitle-hero {
    font-size: 1.1rem;
    opacity: 0.9;
}

/* ===========================
   Main Content
   =========================== */

.main {
    padding: var(--spacing-3xl) 0;
}

.section {
    padding: var(--spacing-3xl) 0;
}

.section-header {
    margin-bottom: var(--spacing-3xl);
}

.section-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    color: var(--color-text-dark);
}

.section-subtitle {
    font-size: 1.05rem;
    color: var(--color-text-gray);
}

/* ===========================
   Articles List
   =========================== */

.articles-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-2xl);
}

.article-item {
    padding: var(--spacing-xl);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    transition: all var(--transition-normal);
    background-color: var(--color-bg-white);
}

.article-item:hover {
    border-color: var(--color-primary);
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.article-item-content {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.article-item-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin: 0;
}

.article-item-title a {
    color: var(--color-text-dark);
    transition: color var(--transition-fast);
}

.article-item-title a:hover {
    color: var(--color-primary);
}

.article-item-excerpt {
    color: var(--color-text-gray);
    font-size: 1rem;
    line-height: 1.6;
}

.article-item-meta {
    display: flex;
    gap: var(--spacing-lg);
    font-size: 0.9rem;
    color: var(--color-text-gray);
}

.article-item-date {
    font-weight: 500;
}

.article-item-read-time {
    color: var(--color-text-gray);
}

/* ===========================
   Footer
   =========================== */

.footer {
    background-color: var(--color-text-dark);
    color: var(--color-bg-white);
    padding: var(--spacing-2xl) 0;
    margin-top: var(--spacing-3xl);
}

.footer-bottom {
    text-align: center;
    color: rgba(255, 255, 255, 0.8);
    font-size: 0.95rem;
}

/* ===========================
   Responsive Design
   =========================== */

@media (max-width: 768px) {
    .header-content {
        flex-direction: column;
        gap: var(--spacing-lg);
    }

    .nav-list {
        gap: var(--spacing-md);
        flex-wrap: wrap;
        justify-content: center;
    }

    .nav-link {
        font-size: 0.85rem;
    }

    .hero-title {
        font-size: 1.75rem;
    }

    .hero-subtitle {
        font-size: 1.1rem;
    }

    .hero-description {
        font-size: 0.95rem;
    }

    .section-header-hero .container {
        flex-direction: column;
        gap: var(--spacing-lg);
    }

    .section-title-hero {
        font-size: 1.75rem;
    }

    .search-wrapper-inline {
        width: 100%;
        right: 0;
    }

    .article-item {
        padding: var(--spacing-lg);
    }

    .article-item-title {
        font-size: 1.25rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-md);
    }

    .logo {
        font-size: 1.25rem;
    }

    .nav-list {
        gap: var(--spacing-sm);
    }

    .nav-link {
        font-size: 0.8rem;
    }

    .hero {
        padding: var(--spacing-2xl) var(--spacing-md);
    }

    .hero-title {
        font-size: 1.5rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .hero-description {
        font-size: 0.9rem;
    }

    .section-header-hero {
        padding: var(--spacing-2xl) var(--spacing-md);
    }

    .section-title-hero {
        font-size: 1.5rem;
    }

    .section-subtitle-hero {
        font-size: 1rem;
    }

    .article-item {
        padding: var(--spacing-md);
    }

    .article-item-title {
        font-size: 1.1rem;
    }

    .article-item-excerpt {
        font-size: 0.95rem;
    }

    .search-wrapper-inline {
        width: 100%;
    }
}

/* ===========================
   Accessibility
   =========================== */

/* Skip to main content link */
.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--color-primary);
    color: white;
    padding: var(--spacing-md);
    text-decoration: none;
    z-index: 100;
    border-radius: var(--radius-md);
}

.skip-link:focus {
    top: 0;
}

/* Focus visible for keyboard navigation */
a:focus-visible,
button:focus-visible,
input:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}