:root {
    --primary: #4F46E5;
    --primary-light: #818CF8;
    --secondary: #EC4899;
    --bg-color: #F8FAFC;
    --text-main: #1E293B;
    --text-muted: #64748B;
    --card-bg: #FFFFFF;
    --accent: #10B981;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-deep: 0 10px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Pretendard', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.6;
    overflow-x: hidden;
    /* Subtle noise texture */
    background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noiseFilter'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.65' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noiseFilter)' opacity='0.03'/%3E%3C/svg%3E");
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

header {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
    color: white;
    padding: 4rem 0;
    text-align: center;
    box-shadow: var(--shadow);
    margin-bottom: 2rem;
}

header h1 {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 1rem;
    letter-spacing: -0.025em;
}

header p {
    font-size: 1.25rem;
    opacity: 0.9;
}

.nav-group {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 3rem;
}

.nav-btn {
    padding: 0.75rem 2rem;
    border-radius: 9999px;
    border: 2px solid var(--primary);
    background: transparent;
    color: var(--primary);
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.nav-btn.active {
    background-color: var(--primary);
    color: white;
}

.nav-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow);
}

.categories-container {
    display: grid;
    gap: 2.5rem;
}

.category-row {
    background: var(--card-bg);
    border-radius: 1.5rem;
    padding: 2rem;
    box-shadow: var(--shadow);
    border: 1px solid rgba(255, 255, 255, 0.5);
}

.category-row h2 {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    color: var(--primary);
    border-left: 4px solid var(--secondary);
    padding-left: 1rem;
}

.subcategory-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
}

.sub-btn {
    padding: 0.5rem 1.25rem;
    border-radius: 0.75rem;
    border: 1px solid #E2E8F0;
    background: #F1F5F9;
    color: var(--text-main);
    font-size: 0.875rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.sub-btn:hover {
    background: white;
    border-color: var(--primary-light);
    color: var(--primary);
    transform: scale(1.05);
    box-shadow: var(--shadow);
}

/* Feature Button Styles */
.feature-btn {
    display: block;
    width: 100%;
    margin-top: 1.5rem;
    padding: 2rem;
    background: white;
    border-radius: 1.5rem;
    border: 2px solid #E2E8F0;
    cursor: pointer;
    transition: var(--transition);
    text-align: center;
    box-shadow: var(--shadow-deep);
}

.feature-btn:hover {
    border-color: var(--primary);
    transform: translateY(-4px);
}

.feature-btn h3 {
    font-size: 1.75rem;
    font-weight: 800;
    margin-bottom: 1.5rem;
    color: var(--primary);
}

.icon-stack {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 1.5rem;
}

.icon-stack svg {
    width: 40px;
    height: 40px;
}

.icon-plus {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-muted);
}

/* Detail View */
.detail-view {
    animation: fadeIn 0.4s ease-out;
}

.hidden {
    display: none;
}

.back-btn {
    margin-bottom: 2rem;
    padding: 0.5rem 1rem;
    background: none;
    border: none;
    color: var(--primary);
    font-weight: 600;
    cursor: pointer;
    font-size: 1.1rem;
}

.hero-section {
    background: linear-gradient(135deg, #1E293B 0%, #0F172A 100%);
    color: white;
    padding: 4rem 2rem;
    border-radius: 2rem;
    text-align: center;
    margin-bottom: 3rem;
}

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

.hero-section p {
    font-size: 1.25rem;
    opacity: 0.8;
}

.structure-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-bottom: 3rem;
}

.structure-card {
    background: white;
    padding: 2rem;
    border-radius: 1.5rem;
    box-shadow: var(--shadow);
    text-align: center;
}

.structure-card h4 {
    color: var(--primary);
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
}

.workflow-section {
    margin-bottom: 3rem;
}

.workflow-step {
    display: flex;
    align-items: flex-start;
    gap: 1.5rem;
    margin-bottom: 1.5rem;
    background: white;
    padding: 1.5rem;
    border-radius: 1rem;
    box-shadow: var(--shadow);
}

.step-number {
    background: var(--primary);
    color: white;
    width: 32px;
    height: 32px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    font-weight: 800;
}

.video-container {
    position: relative;
    padding-bottom: 56.25%;
    height: 0;
    border-radius: 1.5rem;
    overflow: hidden;
    box-shadow: var(--shadow-deep);
}

.video-container iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

footer {
    padding: 4rem 0;
    text-align: center;
    color: var(--text-muted);
    border-top: 1px solid #E2E8F0;
    margin-top: 4rem;
}

@media (max-width: 768px) {
    header h1 { font-size: 2rem; }
    .hero-section h2 { font-size: 1.75rem; }
}