/* ===== 기본 설정 ===== */
:root {
    /* 색상 변수 */
    --primary-color: #4a90e2;
    --secondary-color: #f39c12;
    --success-color: #27ae60;
    --danger-color: #e74c3c;
    --warning-color: #f1c40f;
    
    /* 단계별 색상 */
    --exploration-color: #f1c40f;
    --synthesis-color: #ff9500;
    --deepening-color: #007aff;
    
    /* 중성 색상 */
    --background: #ffffff;
    --surface: #f8f9fa;
    --text-primary: #2c3e50;
    --text-secondary: #6c757d;
    --border-color: #e9ecef;
    
    /* 그림자 */
    --shadow-sm: 0 2px 4px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 8px rgba(0,0,0,0.1);
    --shadow-lg: 0 8px 16px rgba(0,0,0,0.1);
    
    /* 간격 */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    
    /* 글꼴 */
    --font-family: 'Noto Sans KR', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    
    /* 애니메이션 */
    --transition: all 0.3s ease;
}

/* 다크 모드 */
body.dark-mode {
    --background: #1a1a1a;
    --surface: #2d2d2d;
    --text-primary: #e0e0e0;
    --text-secondary: #a0a0a0;
    --border-color: #404040;
}

/* ===== 전역 스타일 ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: var(--font-family);
    background-color: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    transition: var(--transition);
}

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

a:hover {
    color: darken(var(--primary-color), 10%);
}

/* ===== 헤더 ===== */
.header {
    background: var(--surface);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow-sm);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-md) var(--spacing-lg);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
}

.logo-icon {
    font-size: 1.5rem;
}

.nav-menu {
    display: flex;
    align-items: center;
    gap: var(--spacing-lg);
    list-style: none;
}

.nav-link {
    color: var(--text-secondary);
    font-weight: 500;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: 8px;
    transition: var(--transition);
}

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

.theme-toggle {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    padding: var(--spacing-sm);
    border-radius: 8px;
    transition: var(--transition);
}

.theme-toggle:hover {
    background: var(--border-color);
}

/* ===== 히어로 섹션 ===== */
.hero {
    background: linear-gradient(135deg, var(--surface) 0%, var(--background) 100%);
    padding: var(--spacing-xl) var(--spacing-lg);
    text-align: center;
}

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

.hero-title {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-md);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-sm);
}

.hero-emoji {
    font-size: 3rem;
}

.hero-subtitle {
    display: block;
    font-size: 1.25rem;
    color: var(--text-secondary);
    font-weight: 400;
}

.hero-description {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
}

/* ===== 단계 흐름 ===== */
.stage-flow {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: var(--spacing-md);
    margin-top: var(--spacing-xl);
}

.stage-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--surface);
    border-radius: 12px;
    border: 2px solid var(--border-color);
}

.stage-icon {
    font-size: 1.5rem;
}

.flow-arrow {
    color: var(--text-secondary);
    font-size: 1.5rem;
}

/* ===== 단계 설명 스타일 ===== */
.stage-explanation {
    display: grid;
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.stage-explain-item {
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-md);
    padding: var(--spacing-lg);
    background: var(--surface);
    border-radius: 16px;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.stage-explain-item::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 4px;
    background: var(--border-color);
    transition: var(--transition);
}

.stage-explain-item.exploration::before {
    background: var(--exploration-color);
}

.stage-explain-item.synthesis::before {
    background: var(--synthesis-color);
}

.stage-explain-item.deepening::before {
    background: var(--deepening-color);
}

.stage-explain-item:hover {
    transform: translateX(4px);
    box-shadow: var(--shadow-md);
}

.stage-number {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    font-size: 1.5rem;
    font-weight: 700;
    flex-shrink: 0;
    background: var(--border-color);
    color: var(--text-primary);
}

.stage-explain-item.exploration .stage-number {
    background: var(--exploration-color);
    color: var(--text-primary);
}

.stage-explain-item.synthesis .stage-number {
    background: var(--synthesis-color);
    color: white;
}

.stage-explain-item.deepening .stage-number {
    background: var(--deepening-color);
    color: white;
}

.stage-content {
    flex: 1;
}

.stage-content h4 {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-sm);
    font-weight: 600;
}

.stage-content p {
    color: var(--text-secondary);
    line-height: 1.6;
}

/* 다크 모드에서 단계 번호 스타일 */
body.dark-mode .stage-number {
    background: rgba(255,255,255,0.1);
}

body.dark-mode .stage-explain-item.exploration .stage-number {
    background: var(--exploration-color);
    color: #2c3e50;
}

body.dark-mode .stage-explain-item.synthesis .stage-number {
    background: var(--synthesis-color);
}

body.dark-mode .stage-explain-item.deepening .stage-number {
    background: var(--deepening-color);
}

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

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

/* ===== 섹션 ===== */
.section-title {
    font-size: 2rem;
    margin-bottom: var(--spacing-md);
    text-align: center;
}

.section-subtitle {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
}

/* ===== 버튼 ===== */
.btn {
    display: inline-block;
    padding: var(--spacing-sm) var(--spacing-lg);
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

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

/* ===== 푸터 ===== */
.footer {
    background: var(--surface);
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-xl) 0;
    margin-top: var(--spacing-xl);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.footer-section h4 {
    margin-bottom: var(--spacing-sm);
}

.footer-bottom {
    text-align: center;
    color: var(--text-secondary);
    border-top: 1px solid var(--border-color);
    padding-top: var(--spacing-lg);
}

/* ===== 유틸리티 클래스 ===== */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0,0,0,0);
    white-space: nowrap;
    border: 0;
}

.offline-indicator {
    position: fixed;
    top: 80px;
    right: 20px;
    background: var(--warning-color);
    color: var(--text-primary);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: 8px;
    display: none;
    z-index: 1001;
}

body.offline .offline-indicator {
    display: block;
}