/* 
VIKO Academy TOPIK Platform - Main Stylesheet
Version: 4.0.0
Description: 현대적 반응형 CSS 프레임워크
*/

/* ========================================
   🎨 CSS 변수 (커스텀 프로퍼티)
   ======================================== */
:root {
  /* 메인 컬러 팔레트 */
  --primary-color: #4f46e5;
  --primary-light: #818cf8;
  --primary-dark: #3730a3;
  --secondary-color: #7c3aed;
  --accent-color: #f59e0b;
  
  /* 상태 컬러 */
  --success-color: #10b981;
  --warning-color: #f59e0b;
  --error-color: #ef4444;
  --info-color: #3b82f6;
  
  /* 그레이 스케일 */
  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-400: #9ca3af;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2937;
  --gray-900: #111827;
  
  /* 레이아웃 */
  --container-max-width: 1200px;
  --header-height: 70px;
  --sidebar-width: 280px;
  --border-radius: 12px;
  --border-radius-sm: 6px;
  --border-radius-lg: 16px;
  
  /* 그림자 */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  
  /* 애니메이션 */
  --transition-fast: 0.15s ease-in-out;
  --transition-base: 0.25s ease-in-out;
  --transition-slow: 0.35s ease-in-out;
  
  /* 폰트 */
  --font-family-sans: 'Noto Sans KR', 'Noto Sans', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-family-mono: 'Fira Code', Consolas, Monaco, monospace;
  
  /* Z-index 레이어 */
  --z-dropdown: 1000;
  --z-sticky: 1020;
  --z-fixed: 1030;
  --z-modal-backdrop: 1040;
  --z-modal: 1050;
  --z-popover: 1060;
  --z-tooltip: 1070;
  --z-toast: 1080;
}

/* ========================================
   🔄 CSS 리셋 및 기본 스타일
   ======================================== */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

*::before,
*::after {
  box-sizing: border-box;
}

html {
  font-size: 16px;
  line-height: 1.6;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-family-sans);
  font-weight: 400;
  color: var(--gray-700);
  background-color: var(--gray-50);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ========================================
   🏗️ 레이아웃 컴포넌트
   ======================================== */

/* 컨테이너 */
.container {
  width: 100%;
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: 0 1rem;
}

.container-fluid {
  width: 100%;
  padding: 0 1rem;
}

/* 그리드 시스템 */
.row {
  display: flex;
  flex-wrap: wrap;
  margin: 0 -0.75rem;
}

.col {
  flex: 1;
  padding: 0 0.75rem;
}

.col-1 { flex: 0 0 8.333333%; max-width: 8.333333%; }
.col-2 { flex: 0 0 16.666667%; max-width: 16.666667%; }
.col-3 { flex: 0 0 25%; max-width: 25%; }
.col-4 { flex: 0 0 33.333333%; max-width: 33.333333%; }
.col-6 { flex: 0 0 50%; max-width: 50%; }
.col-8 { flex: 0 0 66.666667%; max-width: 66.666667%; }
.col-9 { flex: 0 0 75%; max-width: 75%; }
.col-12 { flex: 0 0 100%; max-width: 100%; }

/* ========================================
   🧭 네비게이션 컴포넌트
   ======================================== */

/* 상단 헤더 */
.topik-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--gray-200);
  z-index: var(--z-fixed);
  transition: var(--transition-base);
}

.topik-header.scrolled {
  box-shadow: var(--shadow-md);
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  padding: 0 1rem;
}

/* 로고 */
.logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  color: var(--gray-900);
  font-weight: 700;
  font-size: 1.25rem;
}

.logo-icon {
  width: 40px;
  height: 40px;
  background: linear-gradient(45deg, var(--primary-color), var(--secondary-color));
  border-radius: var(--border-radius);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 1.25rem;
  font-weight: bold;
}

/* 네비게이션 메뉴 */
.nav-menu {
  display: flex;
  align-items: center;
  gap: 2rem;
  list-style: none;
}

.nav-item {
  position: relative;
}

.nav-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 1rem;
  color: var(--gray-600);
  text-decoration: none;
  font-weight: 500;
  border-radius: var(--border-radius);
  transition: var(--transition-fast);
}

.nav-link:hover,
.nav-link.active {
  color: var(--primary-color);
  background-color: var(--primary-color)10;
}

/* 사용자 메뉴 */
.user-menu {
  position: relative;
  display: flex;
  align-items: center;
  gap: 1rem;
}

/* 사용자 프로필 */
.user-profile {
  position: relative;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.user-avatar {
  width: 36px;
  height: 36px;
  background: var(--primary-color);
  color: white;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition-fast);
}

.user-avatar:hover {
  transform: scale(1.05);
}

/* 사용자 드롭다운 */
.user-dropdown {
  position: absolute;
  top: 100%;
  right: 0;
  background: white;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-lg);
  padding: 1rem;
  min-width: 200px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition: all var(--transition-base);
  z-index: var(--z-dropdown);
}

.user-profile:hover .user-dropdown {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.user-info {
  text-align: center;
  margin-bottom: 1rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--gray-200);
}

.user-info strong {
  display: block;
  color: var(--gray-800);
  font-size: 1rem;
  margin-bottom: 0.25rem;
}

.user-info small {
  color: var(--gray-500);
  font-size: 0.875rem;
}

.user-actions {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.logout-btn {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 1rem;
  color: var(--error-color);
  text-decoration: none;
  border-radius: var(--border-radius-sm);
  transition: var(--transition-fast);
  background: var(--gray-50);
}

.logout-btn:hover {
  background: var(--error-color);
  color: white;
  transform: translateY(-1px);
}

/* 모바일 메뉴 토글 */
.mobile-menu-toggle {
  display: none;
  flex-direction: column;
  gap: 4px;
  padding: 0.5rem;
  background: none;
  border: none;
  cursor: pointer;
}

.mobile-menu-toggle span {
  width: 24px;
  height: 3px;
  background: var(--gray-600);
  border-radius: 2px;
  transition: var(--transition-fast);
}

/* 사이드바 */
.sidebar {
  position: fixed;
  top: var(--header-height);
  left: 0;
  width: var(--sidebar-width);
  height: calc(100vh - var(--header-height));
  background: white;
  border-right: 1px solid var(--gray-200);
  overflow-y: auto;
  transform: translateX(0);
  transition: transform var(--transition-base);
  z-index: var(--z-sticky);
}

.sidebar.collapsed {
  transform: translateX(-100%);
}

.sidebar-content {
  padding: 1.5rem;
}

.sidebar-section {
  margin-bottom: 2rem;
}

.sidebar-title {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--gray-500);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 1rem;
}

.sidebar-menu {
  list-style: none;
}

.sidebar-menu li {
  margin-bottom: 0.25rem;
}

.sidebar-link {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 1rem;
  color: var(--gray-600);
  text-decoration: none;
  border-radius: var(--border-radius);
  transition: var(--transition-fast);
}

.sidebar-link:hover,
.sidebar-link.active {
  color: var(--primary-color);
  background-color: var(--primary-color)10;
}

.sidebar-link .icon {
  font-size: 1.125rem;
}

/* ========================================
   🃏 카드 컴포넌트
   ======================================== */

.card {
  background: white;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
  overflow: hidden;
  transition: var(--transition-base);
}

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

.card-header {
  padding: 1.5rem;
  border-bottom: 1px solid var(--gray-200);
}

.card-title {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--gray-900);
  margin-bottom: 0.5rem;
}

.card-subtitle {
  color: var(--gray-500);
  font-size: 0.875rem;
}

.card-body {
  padding: 1.5rem;
}

.card-footer {
  padding: 1rem 1.5rem;
  background: var(--gray-50);
  border-top: 1px solid var(--gray-200);
}

/* 과정/강의 카드 */
.course-card {
  position: relative;
  overflow: hidden;
}

.course-thumbnail {
  position: relative;
  aspect-ratio: 16/9;
  background: var(--gray-200);
  overflow: hidden;
}

.course-thumbnail img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: var(--transition-slow);
}

.course-card:hover .course-thumbnail img {
  transform: scale(1.05);
}

.course-badge {
  position: absolute;
  top: 1rem;
  right: 1rem;
  padding: 0.25rem 0.75rem;
  background: var(--primary-color);
  color: white;
  font-size: 0.75rem;
  font-weight: 600;
  border-radius: var(--border-radius-sm);
}

.course-info {
  padding: 1.5rem;
}

.course-title {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--gray-900);
  margin-bottom: 0.5rem;
  line-height: 1.4;
}

.course-description {
  color: var(--gray-600);
  font-size: 0.875rem;
  line-height: 1.5;
  margin-bottom: 1rem;
}

.course-meta {
  display: flex;
  align-items: center;
  gap: 1rem;
  font-size: 0.875rem;
  color: var(--gray-500);
  margin-bottom: 1rem;
}

.course-progress {
  margin-bottom: 1rem;
}

/* ========================================
   📊 프로그레스 바
   ======================================== */

.progress {
  width: 100%;
  height: 8px;
  background: var(--gray-200);
  border-radius: 4px;
  overflow: hidden;
  position: relative;
}

.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--primary-color), var(--primary-light));
  border-radius: 4px;
  transition: width var(--transition-slow);
  position: relative;
}

.progress-bar::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(
    90deg,
    transparent,
    rgba(255, 255, 255, 0.3),
    transparent
  );
  animation: progress-shine 2s infinite;
}

@keyframes progress-shine {
  0% { transform: translateX(-100%); }
  100% { transform: translateX(100%); }
}

.progress-text {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.875rem;
  color: var(--gray-600);
  margin-top: 0.5rem;
}

/* 원형 프로그레스 */
.progress-circle {
  position: relative;
  width: 80px;
  height: 80px;
}

.progress-circle svg {
  width: 100%;
  height: 100%;
  transform: rotate(-90deg);
}

.progress-circle .track {
  fill: none;
  stroke: var(--gray-200);
  stroke-width: 8;
}

.progress-circle .progress-path {
  fill: none;
  stroke: var(--primary-color);
  stroke-width: 8;
  stroke-linecap: round;
  transition: stroke-dasharray var(--transition-slow);
}

.progress-circle .progress-value {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-size: 1rem;
  font-weight: 600;
  color: var(--gray-700);
}

/* ========================================
   🗂️ 모달 컴포넌트
   ======================================== */

.modal-backdrop {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.5);
  z-index: var(--z-modal-backdrop);
  opacity: 0;
  visibility: hidden;
  transition: var(--transition-base);
}

.modal-backdrop.show {
  opacity: 1;
  visibility: visible;
}

.modal {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%) scale(0.9);
  background: white;
  border-radius: var(--border-radius-lg);
  box-shadow: var(--shadow-xl);
  z-index: var(--z-modal);
  max-width: 90vw;
  max-height: 90vh;
  overflow: hidden;
  opacity: 0;
  visibility: hidden;
  transition: var(--transition-base);
}

.modal.show {
  opacity: 1;
  visibility: visible;
  transform: translate(-50%, -50%) scale(1);
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.5rem;
  border-bottom: 1px solid var(--gray-200);
}

.modal-title {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--gray-900);
}

.modal-close {
  background: none;
  border: none;
  font-size: 1.5rem;
  color: var(--gray-400);
  cursor: pointer;
  padding: 0.5rem;
  border-radius: var(--border-radius);
  transition: var(--transition-fast);
}

.modal-close:hover {
  color: var(--gray-600);
  background: var(--gray-100);
}

.modal-body {
  padding: 1.5rem;
  overflow-y: auto;
  max-height: calc(90vh - 140px);
}

.modal-footer {
  display: flex;
  justify-content: flex-end;
  gap: 1rem;
  padding: 1.5rem;
  border-top: 1px solid var(--gray-200);
}

/* 모달 크기 */
.modal-sm { width: 400px; }
.modal-md { width: 600px; }
.modal-lg { width: 800px; }
.modal-xl { width: 1200px; }

/* ========================================
   📝 폼 요소
   ======================================== */

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

.form-label {
  display: block;
  font-weight: 500;
  color: var(--gray-700);
  margin-bottom: 0.5rem;
  font-size: 0.875rem;
}

.form-input,
.form-select,
.form-textarea {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1px solid var(--gray-300);
  border-radius: var(--border-radius);
  font-size: 1rem;
  line-height: 1.5;
  transition: var(--transition-fast);
  background: white;
}

.form-input:focus,
.form-select:focus,
.form-textarea:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.form-input::placeholder {
  color: var(--gray-400);
}

.form-textarea {
  resize: vertical;
  min-height: 100px;
}

.form-error {
  color: var(--error-color);
  font-size: 0.875rem;
  margin-top: 0.25rem;
}

.form-help {
  color: var(--gray-500);
  font-size: 0.875rem;
  margin-top: 0.25rem;
}

/* ========================================
   🔘 버튼 컴포넌트
   ======================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  font-size: 0.875rem;
  font-weight: 500;
  line-height: 1;
  text-decoration: none;
  border: 1px solid transparent;
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: var(--transition-fast);
  white-space: nowrap;
  user-select: none;
}

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

/* 버튼 스타일 */
.btn-primary {
  background: var(--primary-color);
  color: white;
  border-color: var(--primary-color);
}

.btn-primary:hover:not(:disabled) {
  background: var(--primary-dark);
  border-color: var(--primary-dark);
  transform: translateY(-1px);
}

.btn-secondary {
  background: var(--gray-200);
  color: var(--gray-700);
  border-color: var(--gray-200);
}

.btn-secondary:hover:not(:disabled) {
  background: var(--gray-300);
  border-color: var(--gray-300);
}

.btn-success {
  background: var(--success-color);
  color: white;
  border-color: var(--success-color);
}

.btn-warning {
  background: var(--warning-color);
  color: white;
  border-color: var(--warning-color);
}

.btn-danger {
  background: var(--error-color);
  color: white;
  border-color: var(--error-color);
}

.btn-outline-primary {
  background: transparent;
  color: var(--primary-color);
  border-color: var(--primary-color);
}

.btn-outline-primary:hover:not(:disabled) {
  background: var(--primary-color);
  color: white;
}

/* 버튼 크기 */
.btn-sm {
  padding: 0.5rem 1rem;
  font-size: 0.8125rem;
}

.btn-lg {
  padding: 1rem 2rem;
  font-size: 1rem;
}

.btn-block {
  width: 100%;
}

/* ========================================
   🌐 언어 전환 컴포넌트
   ======================================== */

.language-switcher {
  position: relative;
  display: inline-block;
}

.language-buttons {
  display: flex;
  gap: 0.25rem;
  background: var(--gray-100);
  border-radius: var(--border-radius);
  padding: 0.25rem;
}

.language-btn {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 0.75rem;
  background: transparent;
  border: none;
  border-radius: var(--border-radius-sm);
  color: var(--gray-600);
  text-decoration: none;
  font-size: 0.8rem;
  font-weight: 500;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.language-btn:hover {
  background: var(--gray-200);
  color: var(--gray-800);
  transform: translateY(-1px);
}

.language-btn.active {
  background: var(--primary-color);
  color: white;
  box-shadow: var(--shadow-sm);
}

.language-btn.active:hover {
  background: var(--primary-dark);
  transform: translateY(-1px);
}

.language-dropdown {
  position: absolute;
  top: 100%;
  right: 0;
  min-width: 150px;
  background: white;
  border: 1px solid var(--gray-200);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-lg);
  z-index: var(--z-dropdown);
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition: var(--transition-fast);
}

.language-dropdown.show {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.language-option {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 1rem;
  color: var(--gray-700);
  text-decoration: none;
  transition: var(--transition-fast);
}

.language-option:hover,
.language-option.active {
  background: var(--primary-color)10;
  color: var(--primary-color);
}

.language-flag {
  width: 20px;
  height: 15px;
  border-radius: 2px;
  object-fit: cover;
}

/* ========================================
   ⚡ 로딩 상태
   ======================================== */

.loading {
  display: inline-block;
  width: 20px;
  height: 20px;
  border: 2px solid var(--gray-200);
  border-radius: 50%;
  border-top-color: var(--primary-color);
  animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.loading-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(255, 255, 255, 0.8);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: var(--z-modal);
  opacity: 0;
  visibility: hidden;
  transition: var(--transition-fast);
}

.loading-overlay.show {
  opacity: 1;
  visibility: visible;
}

.loading-spinner {
  width: 50px;
  height: 50px;
  border: 4px solid var(--gray-200);
  border-radius: 50%;
  border-top-color: var(--primary-color);
  animation: spin 1s linear infinite;
}

/* ========================================
   🔔 알림 및 토스트
   ======================================== */

.toast-container {
  position: fixed;
  top: 1rem;
  right: 1rem;
  z-index: var(--z-toast);
  max-width: 400px;
}

.toast {
  background: white;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-lg);
  border-left: 4px solid var(--primary-color);
  margin-bottom: 1rem;
  padding: 1rem;
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  transform: translateX(100%);
  opacity: 0;
  transition: var(--transition-base);
}

.toast.show {
  transform: translateX(0);
  opacity: 1;
}

.toast-content {
  flex: 1;
}

.toast-title {
  font-weight: 600;
  color: var(--gray-900);
  margin-bottom: 0.25rem;
}

.toast-message {
  color: var(--gray-600);
  font-size: 0.875rem;
}

.toast-close {
  background: none;
  border: none;
  color: var(--gray-400);
  cursor: pointer;
  padding: 0.25rem;
}

.toast.success { border-left-color: var(--success-color); }
.toast.warning { border-left-color: var(--warning-color); }
.toast.error { border-left-color: var(--error-color); }

/* ========================================
   📱 반응형 디자인
   ======================================== */

/* 태블릿 (768px ~ 1024px) */
@media (max-width: 1024px) {
  .sidebar {
    width: 250px;
  }
  
  .container {
    padding: 0 1.5rem;
  }
  
  .nav-menu {
    gap: 1rem;
  }
}

/* 모바일 (~ 768px) */
@media (max-width: 768px) {
  :root {
    --header-height: 60px;
    --sidebar-width: 100%;
  }
  
  .mobile-menu-toggle {
    display: flex;
  }
  
  .nav-menu {
    display: none;
  }
  
  .sidebar {
    width: 100%;
    transform: translateX(-100%);
  }
  
  .sidebar.show {
    transform: translateX(0);
  }
  
  .container {
    padding: 0 1rem;
  }
  
  .modal {
    max-width: 95vw;
    margin: 1rem;
  }
  
  .btn {
    padding: 0.875rem 1.25rem;
  }
  
  .btn-block {
    width: 100%;
  }
  
  /* 그리드 컬럼 모바일 대응 */
  .col-1, .col-2, .col-3, .col-4, 
  .col-6, .col-8, .col-9 {
    flex: 0 0 100%;
    max-width: 100%;
  }
  
  .course-meta {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.5rem;
  }
}

/* 작은 모바일 (~ 480px) */
@media (max-width: 480px) {
  .container {
    padding: 0 0.75rem;
  }
  
  .card-body,
  .card-header {
    padding: 1rem;
  }
  
  .modal-body,
  .modal-header,
  .modal-footer {
    padding: 1rem;
  }
  
  .toast-container {
    left: 1rem;
    right: 1rem;
    max-width: none;
  }
}

/* ========================================
   🎨 유틸리티 클래스
   ======================================== */

/* 텍스트 */
.text-left { text-align: left; }
.text-center { text-align: center; }
.text-right { text-align: right; }

.text-primary { color: var(--primary-color); }
.text-secondary { color: var(--secondary-color); }
.text-success { color: var(--success-color); }
.text-warning { color: var(--warning-color); }
.text-danger { color: var(--error-color); }
.text-muted { color: var(--gray-500); }

.text-xs { font-size: 0.75rem; }
.text-sm { font-size: 0.875rem; }
.text-base { font-size: 1rem; }
.text-lg { font-size: 1.125rem; }
.text-xl { font-size: 1.25rem; }
.text-2xl { font-size: 1.5rem; }

.font-light { font-weight: 300; }
.font-normal { font-weight: 400; }
.font-medium { font-weight: 500; }
.font-semibold { font-weight: 600; }
.font-bold { font-weight: 700; }

/* 간격 */
.m-0 { margin: 0; }
.m-1 { margin: 0.25rem; }
.m-2 { margin: 0.5rem; }
.m-3 { margin: 0.75rem; }
.m-4 { margin: 1rem; }
.m-5 { margin: 1.25rem; }

.mt-0 { margin-top: 0; }
.mt-1 { margin-top: 0.25rem; }
.mt-2 { margin-top: 0.5rem; }
.mt-3 { margin-top: 0.75rem; }
.mt-4 { margin-top: 1rem; }
.mt-5 { margin-top: 1.25rem; }

.mb-0 { margin-bottom: 0; }
.mb-1 { margin-bottom: 0.25rem; }
.mb-2 { margin-bottom: 0.5rem; }
.mb-3 { margin-bottom: 0.75rem; }
.mb-4 { margin-bottom: 1rem; }
.mb-5 { margin-bottom: 1.25rem; }

.p-0 { padding: 0; }
.p-1 { padding: 0.25rem; }
.p-2 { padding: 0.5rem; }
.p-3 { padding: 0.75rem; }
.p-4 { padding: 1rem; }
.p-5 { padding: 1.25rem; }

/* 디스플레이 */
.d-none { display: none; }
.d-block { display: block; }
.d-flex { display: flex; }
.d-inline { display: inline; }
.d-inline-block { display: inline-block; }

/* 플렉스 */
.flex-row { flex-direction: row; }
.flex-column { flex-direction: column; }
.align-start { align-items: flex-start; }
.align-center { align-items: center; }
.align-end { align-items: flex-end; }
.justify-start { justify-content: flex-start; }
.justify-center { justify-content: center; }
.justify-end { justify-content: flex-end; }
.justify-between { justify-content: space-between; }

/* 기타 */
.rounded { border-radius: var(--border-radius); }
.rounded-sm { border-radius: var(--border-radius-sm); }
.rounded-lg { border-radius: var(--border-radius-lg); }

.shadow { box-shadow: var(--shadow); }
.shadow-md { box-shadow: var(--shadow-md); }
.shadow-lg { box-shadow: var(--shadow-lg); }

.cursor-pointer { cursor: pointer; }
.cursor-not-allowed { cursor: not-allowed; }

.overflow-hidden { overflow: hidden; }
.overflow-auto { overflow: auto; }

/* ========================================
   🌙 다크 모드 (준비)
   ======================================== */

@media (prefers-color-scheme: dark) {
  /* 다크 모드 지원 준비 */
}

/* ========================================
   ✨ 애니메이션 및 효과
   ======================================== */

.fade-in {
  animation: fadeIn 0.5s ease-in-out;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

.slide-in-left {
  animation: slideInLeft 0.5s ease-out;
}

@keyframes slideInLeft {
  from { transform: translateX(-100%); }
  to { transform: translateX(0); }
}

.bounce-in {
  animation: bounceIn 0.6s ease-out;
}

@keyframes bounceIn {
  0% { transform: scale(0.3); opacity: 0; }
  50% { transform: scale(1.05); }
  70% { transform: scale(0.9); }
  100% { transform: scale(1); opacity: 1; }
}

/* 마우스 오버 효과 */
.hover-lift {
  transition: transform var(--transition-fast);
}

.hover-lift:hover {
  transform: translateY(-2px);
}

.hover-scale {
  transition: transform var(--transition-fast);
}

.hover-scale:hover {
  transform: scale(1.02);
}

/* ========================================
   🎯 TOPIK 플랫폼 전용 스타일
   ======================================== */

/* 강의실 레이아웃 */
.classroom-container {
  margin-top: var(--header-height);
  min-height: calc(100vh - var(--header-height));
}

.classroom-content {
  margin-left: var(--sidebar-width);
  padding: 2rem;
  transition: margin-left var(--transition-base);
}

.classroom-content.sidebar-collapsed {
  margin-left: 0;
}

/* 비디오 플레이어 */
.video-container {
  position: relative;
  width: 100%;
  max-width: 100%;
  background: #000;
  border-radius: var(--border-radius);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.video-placeholder {
  aspect-ratio: 16/9;
  background: var(--gray-900);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 1.125rem;
}

/* 채팅 인터페이스 */
.chat-container {
  height: 400px;
  display: flex;
  flex-direction: column;
  background: white;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
  overflow: hidden;
}

.chat-messages {
  flex: 1;
  padding: 1rem;
  overflow-y: auto;
}

.chat-message {
  margin-bottom: 1rem;
  padding: 0.75rem;
  border-radius: var(--border-radius);
  background: var(--gray-100);
}

.chat-message.user {
  background: var(--primary-color);
  color: white;
  margin-left: 2rem;
}

.chat-input-container {
  padding: 1rem;
  border-top: 1px solid var(--gray-200);
  display: flex;
  gap: 0.75rem;
}

.chat-input {
  flex: 1;
  border: 1px solid var(--gray-300);
  border-radius: var(--border-radius);
  padding: 0.75rem;
}

/* 반응형 강의실 */
@media (max-width: 768px) {
  .classroom-content {
    margin-left: 0;
    padding: 1rem;
  }
  
  .chat-container {
    height: 300px;
  }
  
  /* 모바일 헤더 최적화 */
  .user-menu {
    gap: 0.5rem;
  }
  
  .language-buttons {
    gap: 0.125rem;
    padding: 0.125rem;
  }
  
  .language-btn {
    padding: 0.375rem 0.5rem;
    font-size: 0.75rem;
  }
  
  .user-profile .user-dropdown {
    right: -50px;
    min-width: 180px;
  }
  
  .logout-btn {
    padding: 0.375rem 0.75rem;
    font-size: 0.875rem;
  }
}
  .chat-message.user {
    margin-left: 1rem;
  }
}