/* ==========================================
   스마트 클래스 자리배치 & 모둠기 - index.css
   Modern Glassmorphism & Light/Dark Theme System
   ========================================== */

/* 1. 디자인 토큰 및 루트 변수 (기본값: 다크 테마 - 클래식 라이브러리 다크) */
:root {
  --font-primary: 'Outfit', 'Noto Sans KR', sans-serif;
  
  /* 다크 테마 변수 (Charcoal Wood & Amber) */
  --bg-main: #141312;
  --bg-gradient: linear-gradient(135deg, #141312 0%, #1e1c1a 100%);
  --accent-color: #d97706;
  --accent-color-rgb: 217, 119, 6;
  --accent-secondary: #b45309;
  --accent-gradient: linear-gradient(135deg, #d97706 0%, #b45309 100%);
  
  --glass-bg: rgba(35, 33, 31, 0.95);
  --glass-bg-hover: rgba(48, 45, 42, 0.98);
  --glass-border: #3d352e;
  --glass-border-focus: #d97706;
  --glass-shadow: 0 10px 40px rgba(0, 0, 0, 0.5);
  
  --text-primary: #f7f5f3;
  --text-secondary: #c5beb6;
  --text-muted: #8c8278;
  --text-accent: #d97706;
  
  --seat-active-bg: #2c2825;
  --seat-active-border: #4a433e;
  --seat-assigned-bg: linear-gradient(135deg, #3d352e 0%, #2f2721 100%);
  --seat-assigned-border: #785028;
  --seat-disabled-bg: rgba(35, 33, 31, 0.3);
  --seat-disabled-border: rgba(61, 53, 46, 0.4);
  
  --success: #84cc16; /* 차분한 그린 */
  --warning: #f59e0b;
  --danger: #ef4444;
  --glow-opacity: 0.15;
}

/* 2. 라이트 테마 변수 오버라이드 (코지 아카데믹 라이트 - Oatmeal Cream & Sage Oak) */
body.light-theme {
  --bg-main: #fdfcfb;
  --bg-gradient: linear-gradient(135deg, #fdfcfb 0%, #f4f2eb 100%);
  
  --glass-bg: #ffffff;
  --glass-bg-hover: #faf9f6;
  --glass-border: #bbb5a8; /* 아주 또렷한 갈색빛 회색 경계선으로 조 카드 등이 눈에 선명히 띔 */
  --glass-border-focus: #4a5c39;
  --glass-shadow: 0 8px 30px rgba(84, 79, 72, 0.08), 0 1px 3px rgba(0, 0, 0, 0.02);
  
  --text-primary: #252422; /* 텍스트 가독성 최적화를 위해 살짝 더 어둡게 */
  --text-secondary: #48433d;
  --text-muted: #827b72;
  --text-accent: #4a5c39; /* 차분한 세이지 그린 어두운 톤 */
  --accent-gradient: linear-gradient(135deg, #5c7a43 0%, #4a5c39 100%);
  --accent-color: #5c7a43;
  --accent-secondary: #8b5a2b;
  
  --seat-active-bg: #f8f7f2;
  --seat-active-border: #999384; /* 활성 빈 자리 점선 테두리를 훨씬 또렷하고 짙게 변경 */
  --seat-assigned-bg: linear-gradient(135deg, #f0f3eb 0%, #dae3d2 100%);
  --seat-assigned-border: #6d805f; /* 배치 완료 자리 테두리를 더 선명하고 묵직한 Sage 세이지 그린으로 강화 */
  --seat-disabled-bg: #e6e3da;
  --seat-disabled-border: #b0ab9b; /* 통로(비활성) 점선 테두리 강화 */
  
  --glow-opacity: 0.05;
}

/* 3. 전역 스타일 & 배경 */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-primary);
  background-color: var(--bg-main);
  background-image: var(--bg-gradient);
  color: var(--text-primary);
  min-height: 100vh;
  overflow-x: hidden;
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 2rem 1rem;
  transition: background-color 0.4s ease, background-image 0.4s ease, color 0.4s ease;
}

/* Ambient Glows */
.bg-glow {
  position: absolute;
  border-radius: 50%;
  filter: blur(120px);
  z-index: 0;
  pointer-events: none;
  opacity: var(--glow-opacity);
  transition: opacity 0.4s ease;
}

.bg-glow-1 {
  width: 450px;
  height: 450px;
  background: var(--accent-color);
  top: -100px;
  right: -50px;
}

.bg-glow-2 {
  width: 550px;
  height: 550px;
  background: var(--accent-secondary);
  bottom: -150px;
  left: -100px;
}

/* 4. 컨테이너 및 헤더 */
.app-container {
  width: 100%;
  max-width: 1440px;
  z-index: 1;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.app-header {
  position: relative;
  text-align: center;
  margin-bottom: 0.5rem;
  padding: 0 4rem;
}

.header-logo {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 0.25rem;
}

.logo-icon {
  width: 2.2rem;
  height: 2.2rem;
  color: var(--text-accent);
}

.app-header h1 {
  font-size: 2.2rem;
  font-weight: 800;
  letter-spacing: -0.03em;
}

.gradient-text {
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.header-subtitle {
  color: var(--text-secondary);
  font-size: 0.95rem;
  font-weight: 400;
  letter-spacing: 0.05em;
}

/* 테마 토글 버튼 */
.theme-toggle-btn {
  position: absolute;
  top: 50%;
  right: 0;
  transform: translateY(-50%);
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  color: var(--text-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  box-shadow: var(--glass-shadow);
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.theme-toggle-btn:hover {
  transform: translateY(-50%) scale(1.1);
  border-color: var(--text-accent);
  box-shadow: 0 0 15px rgba(99, 102, 241, 0.3);
}

.theme-icon {
  width: 1.3rem;
  height: 1.3rem;
  position: absolute;
  transition: transform 0.4s ease, opacity 0.3s ease;
}

/* 기본값: 다크모드이므로 해(Light)가 보이고 달(Dark)이 감춰짐 */
body:not(.light-theme) .sun-icon {
  opacity: 1;
  transform: rotate(0deg) scale(1);
}
body:not(.light-theme) .moon-icon {
  opacity: 0;
  transform: rotate(90deg) scale(0.5);
}

/* 라이트모드 상태: 달(Dark)이 보이고 해(Light)가 감춰짐 */
body.light-theme .sun-icon {
  opacity: 0;
  transform: rotate(-90deg) scale(0.5);
}
body.light-theme .moon-icon {
  opacity: 1;
  transform: rotate(0deg) scale(1);
}

/* 5. 메인 레이아웃 및 카드 */
.main-layout {
  display: grid;
  grid-template-columns: 360px 1fr;
  gap: 1.5rem;
  width: 100%;
}

@media (max-width: 992px) {
  .main-layout {
    grid-template-columns: 1fr;
  }
}

.card {
  background: var(--glass-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--glass-border);
  border-radius: 1.25rem;
  box-shadow: var(--glass-shadow);
  padding: 1.75rem;
  transition: border-color 0.3s ease, box-shadow 0.3s ease, background-color 0.4s ease;
}

.sidebar-panel {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.settings-section {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.section-title {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
  padding-bottom: 0.6rem;
}

body.light-theme .section-title {
  border-bottom-color: rgba(0, 0, 0, 0.05);
}

.section-icon {
  width: 1.25rem;
  height: 1.25rem;
  color: var(--text-accent);
}

.section-title h2 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-primary);
}

/* 6. 학급(그룹) 관리 컴포넌트 */
.class-manager-wrapper {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.select-class-row {
  display: flex;
  gap: 0.5rem;
  width: 100%;
}

.class-select-box {
  flex: 1;
  background: rgba(0, 0, 0, 0.2);
  border: 1px solid var(--glass-border);
  border-radius: 0.6rem;
  padding: 0.6rem 0.8rem;
  color: var(--text-primary);
  font-family: var(--font-primary);
  font-size: 0.85rem;
  font-weight: 600;
  outline: none;
  cursor: pointer;
  transition: border-color 0.2s;
}

body.light-theme .class-select-box {
  background: rgba(255, 255, 255, 0.8);
}

.class-select-box:focus {
  border-color: var(--glass-border-focus);
}

.btn-icon-only {
  width: 38px;
  height: 38px;
  padding: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.save-class-row {
  display: flex;
  gap: 0.5rem;
}

.save-class-row input {
  flex: 1;
  background: rgba(0, 0, 0, 0.25);
  border: 1px solid var(--glass-border);
  border-radius: 0.5rem;
  padding: 0.5rem 0.75rem;
  color: var(--text-primary);
  font-family: var(--font-primary);
  font-size: 0.8rem;
  outline: none;
}

body.light-theme .save-class-row input {
  background: rgba(255, 255, 255, 0.8);
}

.save-class-row input:focus {
  border-color: var(--glass-border-focus);
}

/* 7. 학생 명단 입력 */
.input-container {
  position: relative;
  width: 100%;
}

textarea#student-list {
  width: 100%;
  height: 150px;
  background: rgba(0, 0, 0, 0.25);
  border: 1px solid var(--glass-border);
  border-radius: 0.75rem;
  padding: 0.85rem;
  color: var(--text-primary);
  font-family: var(--font-primary);
  font-size: 0.85rem;
  line-height: 1.5;
  resize: none;
  outline: none;
  transition: border-color 0.2s, box-shadow 0.2s;
}

body.light-theme textarea#student-list {
  background: rgba(255, 255, 255, 0.8);
}

textarea#student-list:focus {
  border-color: var(--glass-border-focus);
  box-shadow: 0 0 12px rgba(99, 102, 241, 0.2);
}

.student-count-badge {
  position: absolute;
  bottom: 10px;
  right: 10px;
  background: var(--accent-gradient);
  color: white;
  font-size: 0.7rem;
  font-weight: 700;
  padding: 0.2rem 0.5rem;
  border-radius: 9999px;
  box-shadow: 0 2px 8px rgba(168, 85, 247, 0.3);
}

/* 슬라이더 및 프리셋 제어 */
.control-group {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.slider-wrapper {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.slider-wrapper label {
  font-size: 0.8rem;
  color: var(--text-secondary);
  display: flex;
  justify-content: space-between;
}

.slider-wrapper label span {
  font-weight: 700;
  color: var(--text-accent);
}

input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 6px;
  border-radius: 9999px;
  background: rgba(255, 255, 255, 0.08);
  outline: none;
}

body.light-theme input[type="range"] {
  background: rgba(0, 0, 0, 0.06);
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent-gradient);
  cursor: pointer;
  box-shadow: 0 0 8px rgba(168, 85, 247, 0.4);
}

/* 프리셋 버튼 */
.preset-wrapper {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.preset-wrapper h3 {
  font-size: 0.8rem;
  color: var(--text-secondary);
  font-weight: 600;
}

.preset-buttons {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.4rem;
}

/* 버튼 정의 */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  font-family: var(--font-primary);
  font-weight: 600;
  border-radius: 0.6rem;
  border: 1px solid transparent;
  cursor: pointer;
  outline: none;
  transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

.btn-primary {
  background: var(--accent-gradient);
  color: #ffffff;
  box-shadow: 0 4px 15px rgba(99, 102, 241, 0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(99, 102, 241, 0.45);
}

.btn-secondary {
  background: rgba(255, 255, 255, 0.04);
  color: var(--text-primary);
  border-color: var(--glass-border);
}

body.light-theme .btn-secondary {
  background: rgba(0, 0, 0, 0.02);
}

.btn-secondary:hover {
  background: var(--glass-bg-hover);
  border-color: rgba(0, 0, 0, 0.15);
}

.btn-sm {
  font-size: 0.75rem;
  padding: 0.45rem 0.6rem;
}

.btn-lg {
  font-size: 1rem;
  padding: 0.85rem 1.5rem;
  border-radius: 0.75rem;
}

.btn-icon {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  font-size: 0.8rem;
}

.btn-svg {
  width: 1.05rem;
  height: 1.05rem;
}

.layout-hint {
  display: flex;
  gap: 0.4rem;
  font-size: 0.7rem;
  color: var(--text-secondary);
  line-height: 1.4;
  background: rgba(99, 102, 241, 0.05);
  border: 1px dashed rgba(99, 102, 241, 0.15);
  padding: 0.6rem;
  border-radius: 0.5rem;
}

.sidebar-footer {
  margin-top: auto;
  font-size: 0.7rem;
  color: var(--text-muted);
  text-align: center;
  border-top: 1px solid rgba(255, 255, 255, 0.03);
  padding-top: 0.75rem;
}

body.light-theme .sidebar-footer {
  border-top-color: rgba(0, 0, 0, 0.04);
}

/* 8. 메인 격자 대형 탭바 */
.main-tabs-nav {
  display: flex;
  gap: 0.75rem;
  border-bottom: 2px solid rgba(255, 255, 255, 0.05);
  padding-bottom: 0.75rem;
  margin-bottom: 0.5rem;
}

body.light-theme .main-tabs-nav {
  border-bottom-color: rgba(0, 0, 0, 0.04);
}

.main-tab-btn {
  flex: 1;
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--glass-border);
  padding: 0.75rem 1rem;
  border-radius: 0.75rem;
  color: var(--text-secondary);
  font-family: var(--font-primary);
  font-weight: 700;
  font-size: 0.9rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  cursor: pointer;
  transition: all 0.25s ease;
}

body.light-theme .main-tab-btn {
  background: rgba(0, 0, 0, 0.01);
  color: var(--text-secondary);
}

/* 다크 테마 활성 탭 (기본) */
.main-tab-btn.active {
  background-color: #d97706 !important; /* Fallback 단색 */
  background: linear-gradient(135deg, #d97706 0%, #b45309 100%) !important;
  color: #ffffff !important;
  border-color: transparent !important;
  box-shadow: 0 4px 15px rgba(217, 119, 6, 0.3) !important;
}

/* 코지 라이트 테마 활성 탭 */
body.light-theme .main-tab-btn.active {
  background-color: #5c7a43 !important; /* Fallback 단색 */
  background: linear-gradient(135deg, #5c7a43 0%, #4a5c39 100%) !important;
  color: #ffffff !important;
  border-color: transparent !important;
  box-shadow: 0 4px 15px rgba(74, 92, 57, 0.25) !important;
}

/* 활성 탭 내부 아이콘 및 텍스트 강제 색상 지정 */
.main-tab-btn.active span,
.main-tab-btn.active svg,
body.light-theme .main-tab-btn.active span,
body.light-theme .main-tab-btn.active svg {
  color: #ffffff !important;
  stroke: #ffffff !important;
  fill: none; /* SVG 내부 채움 억제 */
}

.main-tab-btn:not(.active):hover,
body.light-theme .main-tab-btn:not(.active):hover {
  background: var(--glass-bg-hover);
  color: var(--text-primary);
  border-color: rgba(255, 255, 255, 0.15);
}

.tab-svg-icon {
  width: 1.1rem;
  height: 1.1rem;
}

.main-tab-view {
  display: none;
  flex-direction: column;
  gap: 1.25rem;
  flex: 1;
}

.main-tab-view.active {
  display: flex;
}

/* 9. 교실 자리배치 뷰 전용 스타일 */
.grid-panel {
  display: flex;
  flex-direction: column;
  min-height: 650px;
}

.grid-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.grid-status {
  display: flex;
  gap: 0.5rem;
}

.status-badge {
  font-size: 0.75rem;
  font-weight: 700;
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(255, 255, 255, 0.08);
  padding: 0.3rem 0.6rem;
  border-radius: 0.4rem;
}

body.light-theme .status-badge {
  background: rgba(0, 0, 0, 0.03);
  border-color: rgba(0, 0, 0, 0.06);
}

#classroom-canvas {
  flex: 1;
  background: rgba(10, 10, 15, 0.6);
  border: 1px solid rgba(255, 255, 255, 0.04);
  border-radius: 1rem;
  padding: 1.75rem 1.25rem 1.25rem 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  position: relative;
}

.group-canvas-theme {
  flex: none;
  height: auto;
  min-height: 500px;
  background: rgba(10, 10, 15, 0.6);
  border: 1px solid rgba(255, 255, 255, 0.04);
  border-radius: 1rem;
  padding: 1.75rem 1.25rem 1.25rem 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  position: relative;
}

body.light-theme #classroom-canvas,
body.light-theme .group-canvas-theme {
  background: rgba(255, 255, 255, 0.98);
  border: 2px solid #ccc7b9; /* 칠판 영역/조배치 캔버스 영역의 전체 경계를 굵고 진하게 표현 */
  box-shadow: inset 0 2px 8px rgba(0, 0, 0, 0.03);
}

/* 칠판 & 교탁 인디케이터 */
.classroom-front, .group-front {
  display: flex;
  justify-content: center;
  width: 100%;
}

.blackboard, .group-blackboard {
  background: linear-gradient(180deg, #1e293b 0%, #0f172a 100%);
  border: 4px solid #334155;
  border-radius: 0.5rem;
  width: 280px;
  height: 38px;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.5);
  position: relative;
}

body.light-theme .blackboard,
body.light-theme .group-blackboard {
  background: linear-gradient(180deg, #334155 0%, #1e293b 100%);
  border-color: #475569;
}

.blackboard::after, .group-blackboard::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 20px;
  right: 20px;
  height: 4px;
  background: #f59e0b;
  border-radius: 2px;
}

.chalk-text {
  color: rgba(255, 255, 255, 0.85);
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.35em;
  padding-left: 0.35em;
}

/* 10. 좌석 및 배치표 그리드 */
.seats-grid-container {
  display: grid;
  gap: 0.6rem;
  width: 100%;
  flex: 1;
  align-items: center;
  justify-content: center;
}

.seat-card {
  aspect-ratio: 1.4 / 1;
  min-height: 58px;
  border-radius: 0.6rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
  cursor: pointer;
  transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  user-select: none;
}

.seat-card.active {
  background: var(--seat-active-bg);
  border: 1.5px dashed var(--seat-active-border);
  color: var(--text-secondary);
}

.seat-card.active:hover {
  transform: translateY(-3px) scale(1.02);
  background: rgba(99, 102, 241, 0.15);
  border-color: var(--accent-color);
  box-shadow: 0 4px 12px rgba(99, 102, 241, 0.2);
}

.seat-card.disabled {
  background: var(--seat-disabled-bg);
  border: 1.5px dotted var(--seat-disabled-border);
  color: var(--text-muted);
}

.seat-card.assigned {
  background: var(--seat-assigned-bg);
  border: 1.5px solid var(--seat-assigned-border);
  box-shadow: 0 4px 10px rgba(168, 85, 247, 0.08);
  color: var(--text-primary);
}

body.light-theme .seat-card.assigned {
  box-shadow: 0 4px 8px rgba(147, 51, 234, 0.05);
}

.seat-card.assigned:hover {
  transform: translateY(-2px);
  border-color: var(--accent-secondary);
  box-shadow: 0 6px 15px rgba(168, 85, 247, 0.15);
}

.seat-card.assigned.empty-seat {
  background: rgba(255, 255, 255, 0.01) !important;
  border: 1.5px solid rgba(255, 255, 255, 0.05) !important;
  box-shadow: none !important;
}

body.light-theme .seat-card.assigned.empty-seat {
  background: rgba(0, 0, 0, 0.02) !important;
  border-color: rgba(0, 0, 0, 0.05) !important;
}

.seat-card.assigned.empty-seat .student-name {
  color: var(--text-muted);
  font-weight: 400;
  opacity: 0.35;
}

.seat-index {
  font-size: 0.6rem;
  color: var(--text-muted);
  margin-bottom: 0.15rem;
}

.student-name {
  font-size: 1.05rem;
  font-weight: 800;
  letter-spacing: 0.02em;
  color: var(--text-primary);
}

.pin-indicator {
  position: absolute;
  top: 4px;
  right: 4px;
  width: 13px;
  height: 13px;
  color: #f43f5e;
}

/* 11. 소그룹 조 짜기 뷰 전용 스타일 */
.group-settings-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  align-items: center;
  background: rgba(255, 255, 255, 0.01);
  border: 1px dashed var(--glass-border);
  padding: 1rem;
  border-radius: 0.85rem;
}

body.light-theme .group-settings-row {
  background: rgba(0, 0, 0, 0.01);
  border-color: rgba(0, 0, 0, 0.06);
}

@media (max-width: 768px) {
  .group-settings-row {
    grid-template-columns: 1fr;
    gap: 1rem;
  }
}

.group-slider-wrapper {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.group-slider-wrapper label {
  font-size: 0.85rem;
  color: var(--text-secondary);
  display: flex;
  justify-content: space-between;
  font-weight: 600;
}

.group-slider-wrapper label span {
  color: var(--text-accent);
  font-weight: 800;
}

.group-options-box {
  display: flex;
  justify-content: flex-end;
}

/* 조 짜기 대형 보드판 */
.groups-board-container {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 1rem;
  width: 100%;
  flex: none;
  height: auto;
  align-content: start;
  padding: 0.25rem;
}

.group-empty-placeholder {
  grid-column: 1 / -1;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 240px;
  color: var(--text-muted);
  font-style: italic;
  font-size: 0.9rem;
  border: 2px dashed var(--glass-border);
  border-radius: 0.75rem;
}

/* 개별 조(그룹) 테이블 카드 */
.group-table-card {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--glass-border);
  border-radius: 0.85rem;
  overflow: hidden;
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  display: flex;
  flex-direction: column;
  animation: group-card-fade-in 0.4s cubic-bezier(0, 0, 0.2, 1);
}

body.light-theme .group-table-card {
  background: #ffffff;
  border: 1.5px solid var(--glass-border); /* 선명한 카드 경계선 부여 */
  box-shadow: 0 4px 12px rgba(84, 79, 72, 0.06);
}

.group-table-card:hover {
  transform: translateY(-4px);
  border-color: var(--text-accent);
  box-shadow: 0 8px 20px rgba(99, 102, 241, 0.15);
}

@keyframes group-card-fade-in {
  0% { transform: translateY(15px); opacity: 0; }
  100% { transform: translateY(0); opacity: 1; }
}

.group-table-header {
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.1) 0%, rgba(168, 85, 247, 0.1) 100%);
  border-bottom: 1px solid var(--glass-border);
  padding: 0.6rem 0.85rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.group-title {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.01em;
}

.group-members-count {
  font-size: 0.7rem;
  font-weight: 700;
  background: var(--accent-gradient);
  color: white;
  padding: 0.15rem 0.4rem;
  border-radius: 9999px;
}

.group-members-list {
  padding: 0.75rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  list-style: none;
  flex: 1;
}

.group-member-item {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.05);
  padding: 0.5rem 0.85rem;
  border-radius: 0.5rem;
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

body.light-theme .group-member-item {
  background: #faf9f6;
  border-color: #dcd8cd; /* 조원 개별 칸 테두리 식별성 강화 */
}

.member-icon {
  width: 0.8rem;
  height: 0.8rem;
  color: var(--text-accent);
}

/* 12. 공통 액션 및 셔플 */
.action-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
}

.secondary-actions {
  display: flex;
  gap: 0.6rem;
}

.seat-card.shuffle-roll {
  animation: card-shake 0.15s infinite alternate;
}

.seat-card.shuffle-roll .student-name {
  filter: blur(1.5px);
  color: var(--text-accent);
}

@keyframes card-shake {
  0% { transform: translate(1px, 1px) rotate(0deg); }
  100% { transform: translate(-1px, -1px) rotate(0.5deg); }
}

.group-table-card.group-shuffling {
  animation: group-pulse 0.2s infinite alternate;
}

@keyframes group-pulse {
  0% { transform: scale(0.99); border-color: var(--glass-border); }
  100% { transform: scale(1.01); border-color: var(--accent-secondary); }
}

/* 13. 모달 관련 스타일링 */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(5, 5, 8, 0.85);
  backdrop-filter: blur(8px);
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s ease;
}

.modal-overlay.open {
  opacity: 1;
  pointer-events: auto;
}

.modal-card {
  width: 90%;
  max-width: 580px;
  background: rgba(20, 20, 35, 0.95);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 1.5rem;
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.6);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transform: translateY(20px);
  transition: transform 0.3s ease;
}

body.light-theme .modal-card {
  background: #ffffff;
  border-color: rgba(0, 0, 0, 0.1);
  box-shadow: 0 20px 50px rgba(15, 23, 42, 0.12);
}

.modal-overlay.open .modal-card {
  transform: translateY(0);
}

.modal-header {
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

body.light-theme .modal-header {
  border-bottom-color: rgba(0, 0, 0, 0.06);
}

.modal-logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.modal-logo-icon {
  width: 1.3rem;
  height: 1.3rem;
  color: var(--accent-secondary);
}

.modal-header h2 {
  font-size: 1.15rem;
  font-weight: 700;
}

.btn-close-modal {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  font-size: 1.75rem;
  cursor: pointer;
  line-height: 1;
}

.modal-body {
  padding: 1.5rem;
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.lock-screen {
  align-items: center;
  text-align: center;
  padding: 2.5rem 1.5rem;
}

.lock-desc {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 1.25rem;
}

.password-input-group {
  display: flex;
  gap: 0.5rem;
  width: 100%;
  max-width: 320px;
}

.password-input-group input {
  flex: 1;
  background: rgba(0, 0, 0, 0.4);
  border: 1px solid var(--glass-border);
  border-radius: 0.6rem;
  padding: 0.75rem 1rem;
  color: var(--text-primary);
  font-size: 1rem;
  text-align: center;
  outline: none;
}

body.light-theme .password-input-group input {
  background: rgba(0, 0, 0, 0.03);
}

.error-text {
  color: var(--danger);
  font-size: 0.8rem;
  font-weight: 500;
}

.tab-buttons {
  display: flex;
  border-bottom: 2px solid rgba(255, 255, 255, 0.05);
}

body.light-theme .tab-buttons {
  border-bottom-color: rgba(0, 0, 0, 0.04);
}

.tab-btn {
  flex: 1;
  background: transparent;
  border: none;
  padding: 0.75rem 0.5rem;
  color: var(--text-secondary);
  font-family: var(--font-primary);
  font-weight: 700;
  font-size: 0.85rem;
  cursor: pointer;
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
  transition: all 0.2s;
}

.tab-btn.active {
  color: var(--accent-secondary);
  border-bottom-color: var(--accent-secondary);
}

.tab-content-container {
  min-height: 240px;
}

.tab-content {
  display: none;
  flex-direction: column;
  gap: 1rem;
  padding: 0.5rem 0;
}

.tab-content.active {
  display: flex;
}

.tab-instruction {
  font-size: 0.8rem;
  color: var(--text-secondary);
  line-height: 1.5;
  background: rgba(255, 255, 255, 0.02);
  border-left: 3px solid var(--accent-secondary);
  padding: 0.6rem 0.75rem;
  border-radius: 0 0.4rem 0.4rem 0;
}

body.light-theme .tab-instruction {
  background: rgba(0, 0, 0, 0.01);
}

.lock-setup-form {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.lock-setup-form select,
.select-pair select {
  flex: 1;
  background: rgba(0, 0, 0, 0.3);
  border: 1px solid var(--glass-border);
  border-radius: 0.5rem;
  padding: 0.6rem;
  color: var(--text-primary);
  outline: none;
}

body.light-theme .lock-setup-form select,
body.light-theme .select-pair select {
  background: rgba(255, 255, 255, 0.8);
}

.vs-text {
  color: var(--text-muted);
  font-weight: 700;
  font-size: 0.9rem;
}

.active-rules-list {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.active-rules-list h3 {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--text-secondary);
}

.rules-list {
  list-style: none;
  max-height: 110px;
  overflow-y: auto;
  background: rgba(0, 0, 0, 0.2);
  border-radius: 0.5rem;
  border: 1px solid rgba(255, 255, 255, 0.03);
}

body.light-theme .rules-list {
  background: rgba(0, 0, 0, 0.02);
  border-color: rgba(0, 0, 0, 0.04);
}

.rules-list li {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.45rem 0.75rem;
  font-size: 0.8rem;
}

.btn-delete-rule {
  background: transparent;
  border: none;
  color: var(--danger);
  font-weight: 700;
  cursor: pointer;
}

.modal-footer-settings {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  padding-top: 1rem;
}

body.light-theme .modal-footer-settings {
  border-top-color: rgba(0, 0, 0, 0.06);
}

.toggle-switch-wrapper {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.switch-label {
  font-size: 0.8rem;
  color: var(--text-secondary);
}

/* 토글 슬라이더 */
.switch {
  position: relative;
  display: inline-block;
  width: 42px;
  height: 22px;
  flex-shrink: 0;
}

.switch input {
  opacity: 0;
  width: 0;
  height: 0;
}

.slider.round {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(255, 255, 255, 0.1);
  transition: .3s;
  border-radius: 34px;
  border: 1px solid rgba(255, 255, 255, 0.05);
}

body.light-theme .slider.round {
  background-color: rgba(0, 0, 0, 0.08);
  border-color: rgba(0, 0, 0, 0.03);
}

.slider.round:before {
  position: absolute;
  content: "";
  height: 14px;
  width: 14px;
  left: 3px;
  bottom: 3px;
  background-color: white;
  transition: .3s;
  border-radius: 50%;
}

input:checked + .slider {
  background-color: var(--accent-secondary);
}

input:checked + .slider:before {
  transform: translateX(20px);
}

/* 토스트 알림 */
.toast-container {
  position: fixed;
  top: 20px;
  right: 20px;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  z-index: 9999;
}

.toast {
  background: rgba(20, 20, 30, 0.9);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  padding: 0.6rem 1.1rem;
  border-radius: 0.5rem;
  color: var(--text-primary);
  font-size: 0.8rem;
  font-weight: 600;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  animation: slide-in-toast 0.25s cubic-bezier(0, 0, 0.2, 1);
  transition: opacity 0.2s;
}

body.light-theme .toast {
  background: rgba(255, 255, 255, 0.95);
  border-color: rgba(0, 0, 0, 0.05);
  box-shadow: 0 4px 15px rgba(15, 23, 42, 0.08);
}

.toast.success { border-left: 4px solid var(--success); }
.toast.warning { border-left: 4px solid var(--warning); }
.toast.danger { border-left: 4px solid var(--danger); }

@keyframes slide-in-toast {
  0% { transform: translateX(100%); opacity: 0; }
  100% { transform: translateX(0); opacity: 1; }
}

/* ============================================================================
   14. 랜덤 뽑기 모듈 (Random Picker) & 골든 티켓 (Golden Ticket)
   ============================================================================ */

.picker-golden-ticket {
  position: relative;
  background: linear-gradient(135deg, #fef3c7 0%, #fcd34d 50%, #f59e0b 100%);
  color: #78350f !important;
  border: 2px solid #d97706;
  border-radius: 0.85rem;
  padding: 1.5rem 1.25rem;
  box-shadow: 0 10px 25px rgba(217, 119, 6, 0.18), inset 0 0 15px rgba(255, 255, 255, 0.5);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  min-height: 140px;
  animation: ticket-flip-in 0.6s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
  user-select: none;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.picker-golden-ticket:hover {
  transform: translateY(-5px) scale(1.03);
  box-shadow: 0 15px 30px rgba(217, 119, 6, 0.28), inset 0 0 15px rgba(255, 255, 255, 0.7);
}

/* 티켓 사이드 반원 홈 (Notches) */
.picker-golden-ticket::before,
.picker-golden-ticket::after {
  content: '';
  position: absolute;
  width: 16px;
  height: 16px;
  background: var(--bg-main);
  border-radius: 50%;
  top: 50%;
  transform: translateY(-50%);
  z-index: 2;
  transition: background-color 0.4s ease;
}

.picker-golden-ticket::before {
  left: -9px;
  box-shadow: inset -2px 0 0 #d97706;
}

.picker-golden-ticket::after {
  right: -9px;
  box-shadow: inset 2px 0 0 #d97706;
}

/* 미세 점선 테두리 디자인으로 티켓 느낌 극대화 */
.picker-golden-ticket-inner {
  border: 1px dashed rgba(120, 53, 15, 0.3);
  width: 100%;
  height: 100%;
  border-radius: 0.5rem;
  padding: 0.75rem 0.5rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

/* 롤링 중 상태 */
.picker-golden-ticket.rolling {
  background: linear-gradient(135deg, #f5f4ef 0%, #e5e3da 100%);
  color: var(--text-secondary) !important;
  border-color: var(--glass-border);
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.05);
  animation: ticket-rolling-shake 0.1s infinite alternate;
}

.picker-golden-ticket.rolling::before,
.picker-golden-ticket.rolling::after {
  box-shadow: inset -2px 0 0 var(--glass-border);
}

.picker-golden-ticket.rolling::after {
  box-shadow: inset 2px 0 0 var(--glass-border);
}

.picker-golden-ticket.rolling .student-name {
  filter: blur(1px);
  color: var(--text-accent);
}

/* 애니메이션 정의 */
@keyframes ticket-flip-in {
  0% {
    transform: rotateY(90deg) scale(0.8);
    opacity: 0;
  }
  100% {
    transform: rotateY(0deg) scale(1);
    opacity: 1;
  }
}

@keyframes ticket-rolling-shake {
  0% { transform: translate(1px, 1px) rotate(0.5deg); }
  100% { transform: translate(-1px, -1px) rotate(-0.5deg); }
}

/* ============================================================================
   15. 비밀 격리 제약 설정 사이드바 패널 & 인라인 고정 선택창
   ============================================================================ */

#secret-sidebar-panel {
  max-height: 0;
  opacity: 0;
  overflow: hidden;
  transition: max-height 0.4s cubic-bezier(0.4, 0, 0.2, 1), opacity 0.3s ease, padding 0.3s ease, border-color 0.3s ease;
  padding-top: 0 !important;
  padding-bottom: 0 !important;
  border-top: 1px dashed transparent !important;
  margin-top: 0 !important;
  margin-bottom: 0 !important;
}

#secret-sidebar-panel.show {
  max-height: 600px;
  opacity: 1;
  padding-top: 1.25rem !important;
  padding-bottom: 1.25rem !important;
  border-top: 1px dashed var(--glass-border) !important;
  margin-top: 1rem !important;
}

/* 인라인 고정 선택 드롭다운 */
.seat-lock-select {
  width: 90%;
  max-width: 120px;
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  color: var(--text-primary);
  border: 1.5px solid var(--text-accent);
  border-radius: 0.4rem;
  padding: 0.2rem 0.4rem;
  font-family: var(--font-primary);
  font-size: 0.75rem;
  font-weight: 700;
  outline: none;
  cursor: pointer;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
  margin-top: 0.25rem;
  transition: border-color 0.2s, box-shadow 0.2s;
  text-align: center;
}

body.light-theme .seat-lock-select {
  background: #faf9f6;
  border-color: #5a7247;
  color: #2c2a27;
}

.seat-lock-select:focus {
  border-color: var(--accent-secondary);
  box-shadow: 0 4px 15px rgba(168, 85, 247, 0.25);
}

/* 고정 선택 모드일 때 좌석 카드 애니메이션 */
.seat-card.lock-selecting {
  animation: lock-pulse 1.5s infinite ease-in-out;
}

@keyframes lock-pulse {
  0% { border-color: var(--seat-active-border); box-shadow: none; }
  50% { border-color: var(--accent-secondary); box-shadow: 0 0 10px rgba(168, 85, 247, 0.3); }
  100% { border-color: var(--seat-active-border); box-shadow: none; }
}

.pin-indicator {
  position: absolute;
  top: 4px;
  right: 4px;
  width: 13px;
  height: 13px;
  color: #f43f5e;
  animation: pin-bounce-in 0.35s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
}

@keyframes pin-bounce-in {
  0% { transform: scale(0); opacity: 0; }
  100% { transform: scale(1); opacity: 1; }
}

/* ============================================================================
   16. 모바일 및 태블릿 반응형 미디어 쿼리 (Responsive Layout Optimizations)
   ============================================================================ */
@media (max-width: 768px) {
  body {
    padding: 1rem 0.5rem;
  }

  .app-container {
    gap: 1rem;
  }

  .app-header {
    padding: 0 1rem;
    margin-bottom: 0.25rem;
  }

  .app-header h1 {
    font-size: 1.6rem;
  }

  .logo-icon {
    width: 1.8rem;
    height: 1.8rem;
  }

  .header-subtitle {
    font-size: 0.8rem;
  }

  .card {
    padding: 1.25rem;
    border-radius: 1rem;
  }

  /* 모바일에서 칠판/좌석 그리드 영역 가로 스크롤 가능하도록 하여 글씨 뭉개짐 방지 */
  #classroom-canvas, 
  .group-canvas-theme {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    padding: 1.25rem 0.75rem 0.75rem 0.75rem;
  }

  .seats-grid-container {
    min-width: 580px; /* 모바일에서 6열 배치 등의 이름 카드가 한눈에 또렷이 보이도록 최소 가로 폭 보장 */
  }

  .classroom-front, 
  .group-front {
    min-width: 580px; /* 칠판 영역도 가로 스크롤 범위에 맞춰 고정 */
  }
  
  /* 조 배치의 경우 모바일 세로 레이아웃 최적화 */
  .groups-board-container {
    grid-template-columns: 1fr; /* 1열 배치 */
  }
}

@media (max-width: 576px) {
  /* 하단 액션 버튼 배치 최적화 (가로폭이 너무 좁아질 때 세로 정렬 및 넓게 채우기) */
  .action-footer {
    flex-direction: column;
    align-items: stretch;
    gap: 0.75rem;
  }

  .action-footer .btn-lg {
    width: 100%;
    padding: 0.75rem 1rem;
    font-size: 0.95rem;
  }

  .secondary-actions {
    width: 100%;
    display: flex;
    gap: 0.5rem;
  }

  .secondary-actions .btn {
    flex: 1;
    font-size: 0.8rem;
    padding: 0.6rem 0.4rem;
  }
  
  /* 테마 전환 버튼 위치 조정 */
  .theme-toggle-btn {
    position: relative;
    top: auto;
    right: auto;
    transform: none;
    margin: 0.5rem auto 0 auto;
  }
}

/* 16. html2canvas 캡처 시 강제 오버라이드 */
body.html2canvas-capturing #classroom-canvas,
body.html2canvas-capturing .group-canvas-theme {
  overflow: visible !important;
  height: auto !important;
}

body.html2canvas-capturing .groups-board-container,
body.html2canvas-capturing .seats-grid-container {
  max-height: none !important;
  overflow: visible !important;
}

body.html2canvas-capturing .group-table-card,
body.html2canvas-capturing .seat-card,
body.html2canvas-capturing .group-member-item {
  animation: none !important;
  transition: none !important;
  opacity: 1 !important;
  transform: none !important;
}