/* ============================================
   TheUXLabs Schedule — Design System
   Aesthetic: Clean & Structured
   ============================================ */

/* --- Fonts --- */
@import url('https://fonts.googleapis.com/css2?family=Sora:wght@300;400;500;600;700&family=Noto+Sans+KR:wght@300;400;500;600;700&display=swap');

/* --- Design Tokens --- */
:root {
  /* Typography */
  --font-display: 'Sora', 'Noto Sans KR', sans-serif;
  --font-body: 'Noto Sans KR', 'Sora', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  --text-xs: 0.65rem;
  --text-sm: 0.75rem;
  --text-base: 0.8125rem;
  --text-lg: 0.875rem;
  --text-xl: 1rem;
  --text-2xl: 1.25rem;
  --text-3xl: 1.5rem;

  /* Colors — Black & White */
  --bg: #ffffff;
  --bg-elevated: #ffffff;
  --bg-inset: #f5f5f5;
  --bg-hover: #f7f7f7;

  --border: #e0e0e0;
  --border-light: #ebebeb;
  --border-focus: #1a1a1a;

  --text: #1a1a1a;
  --text-secondary: #666666;
  --text-tertiary: #999999;
  --text-inverse: #ffffff;

  --primary: #1a1a1a;
  --primary-hover: #333333;
  --primary-active: #000000;
  --primary-light: #f5f5f5;
  --primary-lighter: #fafafa;

  --success: #1a1a1a;
  --success-light: #f5f5f5;
  --warning: #1a1a1a;
  --warning-light: #f5f5f5;
  --danger: #1a1a1a;
  --danger-light: #f5f5f5;

  /* Calendar-specific — distinct colors */
  --cal-am: #2563eb;
  --cal-am-bg: #dbeafe;
  --cal-am-border: #93bbfd;
  --cal-pm: #e85d04;
  --cal-pm-bg: #fff1e6;
  --cal-pm-border: #fdba8c;
  --cal-allday: #7c3aed;
  --cal-allday-bg: #ede9fe;
  --cal-allday-border: #c4b5fd;
  --cal-assigned: #dc2626;
  --cal-assigned-bg: #fee2e2;
  --cal-assigned-border: #fca5a5;
  --cal-today: #1a1a1a;
  --cal-today-bg: #f0f0f0;

  /* Spacing (4px base) */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-16: 64px;
  --space-20: 80px;

  /* Radius */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-xl: 20px;

  /* Shadows — warm-tinted */
  --shadow-sm: 0 1px 2px rgba(38, 36, 32, 0.05);
  --shadow-md: 0 2px 8px rgba(38, 36, 32, 0.08), 0 1px 2px rgba(38, 36, 32, 0.04);
  --shadow-lg: 0 8px 24px rgba(38, 36, 32, 0.1), 0 2px 8px rgba(38, 36, 32, 0.04);
  --shadow-xl: 0 16px 48px rgba(38, 36, 32, 0.12), 0 4px 12px rgba(38, 36, 32, 0.06);

  /* Transitions */
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --ease-in-out: cubic-bezier(0.65, 0, 0.35, 1);
  --duration-fast: 150ms;
  --duration-normal: 250ms;
  --duration-slow: 400ms;
}

/* --- Reset --- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

body {
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  min-height: 100dvh;
}

img, svg { display: block; max-width: 100%; }
button, input, select, textarea { font: inherit; color: inherit; }
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

/* --- Typography --- */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 600;
  line-height: 1.25;
  letter-spacing: -0.02em;
  color: var(--text);
}
h1 { font-size: var(--text-3xl); }
h2 { font-size: var(--text-2xl); }
h3 { font-size: var(--text-xl); }
h4 { font-size: var(--text-lg); font-weight: 500; }

.label {
  font-family: var(--font-display);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--text-tertiary);
}

/* --- Layout --- */
.page {
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
}

.page-header {
  background: var(--bg-elevated);
  border-bottom: 1px solid var(--border);
  padding: var(--space-4) var(--space-6);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  position: sticky;
  top: 0;
  z-index: 100;
}

.page-header .logo {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: var(--text-lg);
  color: var(--text);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.page-header .logo span {
  color: #999999;
  font-weight: 400;
}

.page-header nav {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.page-header nav a {
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--text-secondary);
  text-decoration: none;
  transition: all var(--duration-fast) var(--ease-out);
}

.page-header nav a:hover {
  background: var(--bg-hover);
  color: var(--text);
  text-decoration: none;
}

.page-header nav a.active {
  background: #1a1a1a;
  color: #ffffff;
}

.page-content {
  flex: 1;
  padding: var(--space-8) var(--space-6);
  max-width: 1200px;
  width: 100%;
  margin: 0 auto;
}

.page-title {
  margin-bottom: var(--space-8);
}

.page-title h1 {
  margin-bottom: var(--space-2);
}

.page-title p {
  color: var(--text-secondary);
  font-size: var(--text-lg);
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-5);
  border-radius: var(--radius-sm);
  font-family: var(--font-display);
  font-size: var(--text-sm);
  font-weight: 500;
  border: 1px solid transparent;
  cursor: pointer;
  transition: all var(--duration-fast) var(--ease-out);
  white-space: nowrap;
  height: 34px;
}

.btn:active { transform: scale(0.98); }

.btn-primary {
  background: #1a1a1a;
  color: #ffffff;
  border-color: #1a1a1a;
}
.btn-primary:hover { background: #333333; border-color: #333333; }
.btn-primary:active { background: #000000; }

.btn-secondary {
  background: var(--bg-elevated);
  color: var(--text);
  border-color: var(--border);
}
.btn-secondary:hover { background: var(--bg-hover); border-color: var(--border); }

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
}
.btn-ghost:hover { background: var(--bg-hover); color: var(--text); }

.btn-danger {
  background: #ffffff;
  color: #1a1a1a;
  border-color: #1a1a1a;
}
.btn-danger:hover { background: #f5f5f5; }

.btn-sm { height: 28px; padding: var(--space-1) var(--space-3); font-size: var(--text-xs); }
.btn-lg { height: 40px; padding: var(--space-3) var(--space-8); font-size: var(--text-sm); }
.btn-full { width: 100%; }

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  pointer-events: none;
}

/* --- Forms --- */
.form-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.form-label {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--text);
}

.form-input,
.form-select,
.form-textarea {
  width: 100%;
  height: 36px;
  padding: 0 var(--space-4);
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: var(--text-base);
  color: var(--text);
  transition: border-color var(--duration-fast) var(--ease-out), box-shadow var(--duration-fast) var(--ease-out);
  outline: none;
}

.form-input:focus,
.form-select:focus,
.form-textarea:focus {
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px rgba(26, 26, 26, 0.08);
}

.form-input::placeholder { color: var(--text-tertiary); }

.form-textarea {
  height: auto;
  min-height: 80px;
  padding: var(--space-3) var(--space-4);
  resize: vertical;
}

.form-select {
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%236e6a62' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  padding-right: 36px;
}

.form-error {
  font-size: var(--text-xs);
  color: var(--danger);
}

.form-hint {
  font-size: var(--text-xs);
  color: var(--text-tertiary);
}

/* --- Cards --- */
.card {
  background: var(--bg-elevated);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-md);
  padding: var(--space-6);
  transition: box-shadow var(--duration-normal) var(--ease-out);
}

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

.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  margin-bottom: var(--space-5);
}

.card-header h3 {
  margin: 0;
}

/* --- Badge --- */
.badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 2px var(--space-2);
  border-radius: 100px;
  font-family: var(--font-display);
  font-size: var(--text-xs);
  font-weight: 600;
  white-space: nowrap;
}

.badge-new { background: #1a1a1a; color: #ffffff; }
.badge-accepted { background: #e0e0e0; color: #1a1a1a; }
.badge-rejected { background: #f5f5f5; color: #999999; text-decoration: line-through; }
.badge-done { background: #f5f5f5; color: #999999; }
.badge-pending { background: #f5f5f5; color: #666666; }
.badge-am { background: var(--cal-am-bg); color: var(--cal-am); border: 1px solid var(--cal-am-border); }
.badge-pm { background: var(--cal-pm-bg); color: var(--cal-pm); border: 1px solid var(--cal-pm-border); }
.badge-allday { background: var(--cal-allday-bg); color: var(--cal-allday); border: 1px solid var(--cal-allday-border); }

/* --- Modal --- */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(38, 36, 32, 0.4);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--duration-normal) var(--ease-out), visibility var(--duration-normal);
  padding: var(--space-4);
}

.modal-overlay.active {
  opacity: 1;
  visibility: visible;
}

.modal {
  background: var(--bg-elevated);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-xl);
  width: 100%;
  max-width: 480px;
  max-height: 90dvh;
  overflow-y: auto;
  transform: translateY(16px) scale(0.97);
  transition: transform var(--duration-normal) var(--ease-out);
}

.modal-overlay.active .modal {
  transform: translateY(0) scale(1);
}

.modal-header {
  padding: var(--space-6) var(--space-6) 0;
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-4);
}

.modal-header h3 {
  margin: 0;
}

.modal-close {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-sm);
  border: none;
  background: transparent;
  color: var(--text-tertiary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: all var(--duration-fast) var(--ease-out);
}

.modal-close:hover { background: var(--bg-hover); color: var(--text); }

.modal-body {
  padding: var(--space-5) var(--space-6);
}

.modal-footer {
  padding: 0 var(--space-6) var(--space-6);
  display: flex;
  gap: var(--space-3);
  justify-content: flex-end;
}

/* --- Calendar --- */
.calendar {
  background: var(--bg-elevated);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.calendar-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-5) var(--space-6);
  border-bottom: 1px solid var(--border-light);
}

.calendar-nav h2 {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  font-weight: 600;
}

.calendar-nav-btns {
  display: flex;
  gap: var(--space-1);
}

.calendar-weekdays {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  border-bottom: 1px solid var(--border-light);
}

.calendar-weekday {
  padding: var(--space-3) var(--space-2);
  text-align: center;
  font-family: var(--font-display);
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.calendar-weekday:first-child { color: var(--danger); }
.calendar-weekday:last-child { color: var(--primary); }

.calendar-grid {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
}

.calendar-day {
  padding: var(--space-2);
  border-right: 1px solid var(--border-light);
  border-bottom: 1px solid var(--border-light);
  cursor: pointer;
  transition: background var(--duration-fast) var(--ease-out);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  position: relative;
  min-height: 90px;
}

.calendar-day:nth-child(7n) { border-right: none; }
.calendar-day:hover { background: var(--bg-hover); }

.calendar-day.other-month {
  opacity: 0.3;
  pointer-events: none;
}

.calendar-day.weekend-disabled {
  background: #fafafa;
  cursor: default;
  pointer-events: none;
}

.calendar-day.weekend-disabled .day-number {
  color: #ccc !important;
}

.calendar-day.past-disabled {
  background: #f5f5f5;
  pointer-events: none;
}

.calendar-day.past-disabled .day-number {
  color: #ccc !important;
}

.calendar-day.today .day-number {
  background: var(--cal-today);
  color: var(--text-inverse);
  border-radius: 50%;
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.calendar-day .day-number {
  font-family: var(--font-display);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--text);
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.calendar-day:nth-child(7n+1) .day-number { color: var(--danger); }
.calendar-day:nth-child(7n) .day-number { color: var(--primary); }

.calendar-day .day-tags {
  display: flex;
  flex-direction: column;
  gap: 2px;
  width: 100%;
  padding: 0 2px;
  margin-top: 2px;
}

.calendar-day .day-tag {
  font-family: var(--font-display);
  font-size: 0.55rem;
  font-weight: 700;
  padding: 2px 6px;
  border-radius: 100px;
  text-align: center;
  line-height: 1.3;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  border: none;
}

.day-tag-am {
  background: var(--cal-am);
  color: #ffffff;
}

.day-tag-pm {
  background: var(--cal-pm);
  color: #ffffff;
}

.day-tag-allday {
  background: var(--cal-allday);
  color: #ffffff;
}

.day-tag-assigned {
  background: var(--cal-assigned);
  color: #ffffff;
}

/* Legend dots */
.legend-dot {
  display: inline-block;
  width: 10px;
  height: 10px;
  border-radius: 50%;
}
.legend-am { background: var(--cal-am); }
.legend-pm { background: var(--cal-pm); }
.legend-allday { background: var(--cal-allday); }
.legend-assigned { background: var(--cal-assigned); }

/* Legacy dot */
.dot { display: inline-block; width: 8px; height: 8px; border-radius: 50%; }
.dot-am { background: var(--cal-am); }
.dot-pm { background: var(--cal-pm); }
.dot-allday { background: var(--cal-allday); }
.dot-assigned { background: var(--cal-assigned); }

/* Admin calendar — show count badge */
.calendar-day .availability-count {
  font-family: var(--font-display);
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--primary);
  background: var(--primary-light);
  border-radius: 100px;
  padding: 1px 6px;
  margin-top: 2px;
}

/* --- Lecture Card --- */
.lecture-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-md);
  padding: var(--space-5);
  display: flex;
  gap: var(--space-5);
  transition: box-shadow var(--duration-normal) var(--ease-out);
}

.lecture-card:hover {
  box-shadow: var(--shadow-md);
}

.lecture-card .date-block {
  text-align: center;
  min-width: 56px;
  flex-shrink: 0;
}

.lecture-card .date-block .month {
  font-family: var(--font-display);
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--primary);
  text-transform: uppercase;
}

.lecture-card .date-block .day {
  font-family: var(--font-display);
  font-size: var(--text-2xl);
  font-weight: 700;
  color: var(--text);
  line-height: 1.1;
}

.lecture-card .date-block .weekday {
  font-size: var(--text-xs);
  color: var(--text-tertiary);
}

.lecture-card .info {
  flex: 1;
  min-width: 0;
}

.lecture-card .info h4 {
  margin-bottom: var(--space-1);
}

.lecture-card .info .meta {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.lecture-card .actions {
  display: flex;
  gap: var(--space-2);
  align-self: flex-start;
  flex-shrink: 0;
}

/* --- Table --- */
.data-table {
  width: 100%;
  border-collapse: collapse;
}

.data-table th {
  font-family: var(--font-display);
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  text-align: left;
  padding: var(--space-3) var(--space-4);
  border-bottom: 2px solid var(--border);
}

.data-table td {
  padding: var(--space-3) var(--space-4);
  border-bottom: 1px solid var(--border-light);
  font-size: var(--text-sm);
}

.data-table tr:hover td {
  background: var(--bg-hover);
}

/* --- Empty State --- */
.empty-state {
  text-align: center;
  padding: var(--space-16) var(--space-8);
  color: var(--text-secondary);
}

.empty-state svg {
  width: 48px;
  height: 48px;
  margin: 0 auto var(--space-4);
  color: var(--text-tertiary);
}

.empty-state h3 {
  color: var(--text);
  margin-bottom: var(--space-2);
}

/* --- Login Page --- */
.login-page {
  min-height: 100dvh;
  display: grid;
  grid-template-columns: 1fr 1fr;
}

.login-brand {
  background: #1a1a1a;
  padding: var(--space-16) var(--space-12);
  display: flex;
  flex-direction: column;
  justify-content: center;
  position: relative;
  overflow: hidden;
}

.login-brand::before {
  content: '';
  position: absolute;
  inset: 0;
  background: none;
}

.login-brand > * { position: relative; z-index: 1; }

.login-brand h1 {
  font-family: var(--font-display);
  font-size: var(--text-3xl);
  color: #ffffff;
  margin-bottom: var(--space-4);
  letter-spacing: -0.03em;
}

.login-brand p {
  color: rgba(255, 255, 255, 0.5);
  font-size: var(--text-sm);
  line-height: 1.7;
  max-width: 400px;
}

.login-brand .brand-logo {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: var(--text-sm);
  color: #ffffff;
  margin-bottom: var(--space-16);
  opacity: 0.7;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.login-form-wrapper {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-12);
}

.login-form {
  width: 100%;
  max-width: 380px;
}

.login-form h2 {
  margin-bottom: var(--space-2);
}

.login-form .subtitle {
  color: var(--text-secondary);
  margin-bottom: var(--space-10);
}

.login-form .form-group + .form-group {
  margin-top: var(--space-5);
}

.login-form .btn {
  margin-top: var(--space-8);
}

.login-form .login-error {
  margin-top: var(--space-4);
  padding: var(--space-3) var(--space-4);
  background: var(--danger-light);
  border-radius: var(--radius-sm);
  color: var(--danger);
  font-size: var(--text-sm);
  display: none;
}

.login-form .login-error.visible {
  display: block;
}

/* --- Tabs --- */
.tabs {
  display: flex;
  gap: var(--space-1);
  border-bottom: 1px solid var(--border);
  margin-bottom: var(--space-6);
}

.tab {
  padding: var(--space-3) var(--space-5);
  font-family: var(--font-display);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--text-secondary);
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  cursor: pointer;
  transition: all var(--duration-fast) var(--ease-out);
  margin-bottom: -1px;
}

.tab:hover { color: var(--text); }
.tab.active {
  color: var(--primary);
  border-bottom-color: var(--primary);
}

.tab-panel { display: none; }
.tab-panel.active { display: block; }

/* --- Toggle / Chip Select --- */
.chip-group {
  display: flex;
  gap: var(--space-2);
  flex-wrap: wrap;
}

.chip {
  padding: var(--space-2) var(--space-4);
  border-radius: 100px;
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  font-size: var(--text-sm);
  cursor: pointer;
  transition: all var(--duration-fast) var(--ease-out);
}

.chip:hover { border-color: var(--primary); }
.chip.selected {
  background: #1a1a1a;
  border-color: #1a1a1a;
  color: #ffffff;
}

/* --- Filters Bar --- */
.filters-bar {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  flex-wrap: wrap;
  margin-bottom: var(--space-6);
}

/* --- Availability Slot Select (in modal) --- */
.slot-options {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-3);
}

.slot-option {
  padding: var(--space-4);
  border: 2px solid var(--border);
  border-radius: var(--radius-md);
  text-align: center;
  cursor: pointer;
  transition: all var(--duration-fast) var(--ease-out);
}

.slot-option:hover { border-color: var(--primary); }

.slot-option.selected {
  border-color: #1a1a1a;
  background: #f5f5f5;
}

.slot-option .slot-icon {
  font-size: 1.5rem;
  margin-bottom: var(--space-2);
}

.slot-option .slot-label {
  font-family: var(--font-display);
  font-size: var(--text-sm);
  font-weight: 600;
}

.slot-option .slot-time {
  font-size: var(--text-xs);
  color: var(--text-secondary);
  margin-top: 2px;
}

/* --- Time Picker (custom) --- */
.time-picker {
  display: none;
  gap: var(--space-3);
  align-items: center;
  margin-top: var(--space-4);
}

.time-picker.visible {
  display: flex;
}

.time-picker input[type="time"] {
  height: 40px;
  padding: 0 var(--space-3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-family: var(--font-display);
  font-size: var(--text-sm);
  outline: none;
}

.time-picker input[type="time"]:focus {
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px rgba(26, 26, 26, 0.08);
}

/* --- Loading --- */
.spinner {
  width: 20px;
  height: 20px;
  border: 2px solid var(--border);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

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

.loading-overlay {
  position: absolute;
  inset: 0;
  background: rgba(255, 255, 255, 0.7);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10;
  border-radius: inherit;
}

/* --- Toast --- */
.toast-container {
  position: fixed;
  top: var(--space-6);
  right: var(--space-6);
  z-index: 2000;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.toast {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: var(--space-4) var(--space-5);
  box-shadow: var(--shadow-lg);
  font-size: var(--text-sm);
  min-width: 280px;
  max-width: 400px;
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  animation: slideIn var(--duration-normal) var(--ease-out);
}

.toast.toast-success { border-left: 3px solid var(--success); }
.toast.toast-error { border-left: 3px solid var(--danger); }
.toast.toast-info { border-left: 3px solid var(--primary); }

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateX(20px);
  }
}

/* --- Animations --- */
@keyframes fadeIn {
  from { opacity: 0; }
}

@keyframes slideUp {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
}

.animate-in {
  animation: slideUp var(--duration-normal) var(--ease-out) both;
}

.stagger-1 { animation-delay: 50ms; }
.stagger-2 { animation-delay: 100ms; }
.stagger-3 { animation-delay: 150ms; }
.stagger-4 { animation-delay: 200ms; }

/* --- Sidebar Panel (Admin: instructor list on date click) --- */
.side-panel {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  width: 380px;
  max-width: 90vw;
  background: var(--bg-elevated);
  border-left: 1px solid var(--border);
  box-shadow: var(--shadow-xl);
  z-index: 500;
  transform: translateX(100%);
  transition: transform var(--duration-normal) var(--ease-out);
  display: flex;
  flex-direction: column;
}

.side-panel.open {
  transform: translateX(0);
}

.side-panel-header {
  padding: var(--space-6);
  border-bottom: 1px solid var(--border-light);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.side-panel-body {
  padding: var(--space-6);
  flex: 1;
  overflow-y: auto;
}

/* --- Responsive --- */
@media (max-width: 768px) {
  .login-page {
    grid-template-columns: 1fr;
  }

  .login-brand {
    padding: var(--space-10) var(--space-6);
    min-height: auto;
  }

  .login-brand h1 { font-size: var(--text-2xl); }
  .login-brand .brand-logo { margin-bottom: var(--space-8); }

  .login-form-wrapper {
    padding: var(--space-8) var(--space-6);
  }

  .page-header {
    padding: var(--space-3) var(--space-4);
  }

  .page-header nav {
    display: none;
  }

  .page-header .mobile-nav-toggle {
    display: flex;
  }

  .page-content {
    padding: var(--space-6) var(--space-4);
  }

  .calendar-day {
    min-height: 56px;
    aspect-ratio: auto;
    padding: var(--space-1);
  }

  .calendar-day .day-number {
    font-size: var(--text-xs);
    width: 24px;
    height: 24px;
  }

  .calendar-day .day-dots .dot {
    width: 4px;
    height: 4px;
  }

  .lecture-card {
    flex-direction: column;
    gap: var(--space-3);
  }

  .lecture-card .date-block {
    display: flex;
    align-items: baseline;
    gap: var(--space-2);
  }

  .lecture-card .date-block .day {
    font-size: var(--text-xl);
  }

  .lecture-card .actions {
    align-self: stretch;
  }

  .lecture-card .actions .btn {
    flex: 1;
  }

  .slot-options {
    grid-template-columns: 1fr;
  }

  .side-panel {
    width: 100%;
  }

  .filters-bar {
    flex-direction: column;
    align-items: stretch;
  }

  .data-table {
    font-size: var(--text-xs);
  }

  .data-table th,
  .data-table td {
    padding: var(--space-2) var(--space-3);
  }
}

@media (max-width: 480px) {
  .calendar-nav h2 {
    font-size: var(--text-lg);
  }
}

/* --- Lecture Popover --- */
.lecture-popover {
  position: fixed;
  z-index: 300;
  background: #1a1a1a;
  color: #ffffff;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-xl);
  padding: var(--space-5);
  width: 280px;
  animation: slideUp var(--duration-normal) var(--ease-out);
}

.lecture-popover .popover-close {
  position: absolute;
  top: var(--space-2);
  right: var(--space-2);
  background: none;
  border: none;
  color: rgba(255,255,255,0.4);
  cursor: pointer;
  padding: 4px;
}

.lecture-popover .popover-close:hover { color: #ffffff; }

.lecture-popover .popover-client {
  font-family: var(--font-display);
  font-size: var(--text-base);
  font-weight: 700;
  margin-bottom: var(--space-1);
}

.lecture-popover .popover-topic {
  font-size: var(--text-sm);
  color: rgba(255,255,255,0.7);
  margin-bottom: var(--space-4);
}

.lecture-popover .popover-meta {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  font-size: var(--text-xs);
}

.lecture-popover .popover-meta-row {
  display: flex;
  gap: var(--space-2);
  align-items: flex-start;
}

.lecture-popover .popover-meta-label {
  color: rgba(255,255,255,0.4);
  min-width: 36px;
  flex-shrink: 0;
}

.lecture-popover .popover-meta-value {
  color: rgba(255,255,255,0.9);
}

.lecture-popover .popover-link {
  display: block;
  margin-top: var(--space-4);
  padding-top: var(--space-3);
  border-top: 1px solid rgba(255,255,255,0.1);
  font-size: var(--text-xs);
  color: rgba(255,255,255,0.5);
  text-decoration: underline;
  cursor: pointer;
  background: none;
  border-left: none;
  border-right: none;
  border-bottom: none;
  text-align: left;
  width: 100%;
}

.lecture-popover .popover-link:hover { color: #ffffff; }

/* --- Onboarding Guide --- */
.onboarding {
  display: none;
  margin-bottom: var(--space-6);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  overflow: hidden;
  animation: slideUp var(--duration-normal) var(--ease-out);
  position: relative;
}

.onboarding.visible { display: block; }

.onboarding-close {
  position: absolute;
  top: var(--space-3);
  right: var(--space-3);
  background: none;
  border: none;
  color: var(--text-tertiary);
  cursor: pointer;
  z-index: 2;
  padding: 4px;
}
.onboarding-close:hover { color: var(--text); }

.onboarding-title {
  font-family: var(--font-display);
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--text);
  padding: var(--space-4) var(--space-5);
  border-bottom: 1px solid var(--border-light);
  letter-spacing: -0.01em;
}

.onboarding-steps {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
}

.onboarding-step {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  padding: var(--space-5);
  font-size: var(--text-xs);
  color: var(--text-secondary);
  line-height: 1.6;
  border-right: 1px solid var(--border-light);
  position: relative;
}

.onboarding-step:last-child { border-right: none; }

.onboarding-num {
  width: 20px;
  height: 20px;
  min-width: 20px;
  border-radius: 50%;
  background: var(--text);
  color: #ffffff;
  font-family: var(--font-display);
  font-size: 0.6rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--space-1);
}

.onboarding-step strong {
  color: var(--text);
  font-weight: 600;
}

.onboarding-footer {
  padding: var(--space-3) var(--space-5);
  border-top: 1px solid var(--border-light);
  display: flex;
  justify-content: flex-end;
}

@media (max-width: 768px) {
  .onboarding-steps {
    grid-template-columns: 1fr 1fr;
  }
  .onboarding-step:nth-child(2) { border-right: none; }
  .onboarding-step:nth-child(2) { border-bottom: 1px solid var(--border-light); }
  .onboarding-step:nth-child(1) { border-bottom: 1px solid var(--border-light); }
}

@media (max-width: 480px) {
  .onboarding-steps {
    grid-template-columns: 1fr;
  }
  .onboarding-step { border-right: none; border-bottom: 1px solid var(--border-light); }
  .onboarding-step:last-child { border-bottom: none; }
}

/* --- Bulk Guide --- */
.bulk-guide {
  display: none;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-4) var(--space-5);
  margin-bottom: var(--space-4);
  background: #ffe03a;
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 600;
  color: #1a1a1a;
  animation: slideUp var(--duration-normal) var(--ease-out);
}

.bulk-guide.visible { display: flex; }

.bulk-guide-step {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: #1a1a1a;
  color: #ffe03a;
  font-family: var(--font-display);
  font-size: 0.65rem;
  font-weight: 700;
  flex-shrink: 0;
}

.bulk-guide-sep {
  color: #666;
  margin: 0 var(--space-1);
}

@media (max-width: 768px) {
  .bulk-guide {
    font-size: var(--text-xs);
    flex-wrap: wrap;
  }
}

/* --- Multi-Select Mode --- */
.calendar.multiselect {
  border: 2px dashed var(--border);
}

.calendar.multiselect .calendar-day:not(.other-month) {
  cursor: pointer;
  user-select: none;
  -webkit-user-select: none;
}

.calendar-day.selected-bulk {
  background: #fff9db !important;
  outline: 2px solid #ffe03a;
  outline-offset: -2px;
  position: relative;
}

.calendar-day.selected-bulk::after {
  content: '\2713';
  position: absolute;
  top: 3px;
  right: 5px;
  font-size: 0.6rem;
  font-weight: 800;
  color: #1a1a1a;
  background: #ffe03a;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  line-height: 1;
}

/* Bulk Action Bar */
.bulk-action-bar {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background: #ffe03a;
  color: #1a1a1a;
  padding: var(--space-4) var(--space-6);
  display: flex;
  align-items: center;
  gap: var(--space-4);
  z-index: 200;
  transform: translateY(100%);
  transition: transform var(--duration-normal) var(--ease-out);
  box-shadow: 0 -4px 24px rgba(0,0,0,0.2);
}

.bulk-action-bar.visible {
  transform: translateY(0);
}

.bulk-action-bar .bulk-count {
  font-family: var(--font-display);
  font-size: var(--text-base);
  font-weight: 600;
  white-space: nowrap;
  min-width: 100px;
}

.bulk-action-bar .bulk-count strong {
  font-size: var(--text-xl);
  font-weight: 800;
}

.bulk-action-bar .bulk-slots {
  display: flex;
  gap: var(--space-2);
  flex: 1;
}

.bulk-slot-chip {
  padding: var(--space-2) var(--space-4);
  border-radius: 100px;
  font-family: var(--font-display);
  font-size: var(--text-sm);
  font-weight: 700;
  cursor: pointer;
  border: 2px solid transparent;
  transition: all var(--duration-fast) var(--ease-out);
}

.bulk-slot-chip:hover { transform: scale(1.05); }

.bulk-slot-chip.active { border-color: #1a1a1a; transform: scale(1.08); box-shadow: 0 2px 8px rgba(0,0,0,0.2); }

.bulk-slot-chip[data-slot="AM"] {
  background: var(--cal-am);
  color: #ffffff;
}
.bulk-slot-chip[data-slot="PM"] {
  background: var(--cal-pm);
  color: #ffffff;
}
.bulk-slot-chip[data-slot="ALLDAY"] {
  background: var(--cal-allday);
  color: #ffffff;
}

.bulk-action-bar .bulk-actions {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.bulk-action-bar .btn-bulk-apply {
  background: #1a1a1a;
  color: #ffe03a;
  border: none;
  padding: var(--space-2) var(--space-5);
  border-radius: var(--radius-sm);
  font-family: var(--font-display);
  font-size: var(--text-sm);
  font-weight: 600;
  cursor: pointer;
  height: 34px;
  transition: all var(--duration-fast) var(--ease-out);
}

.bulk-action-bar .btn-bulk-apply:hover { background: #333; }
.bulk-action-bar .btn-bulk-apply:disabled { opacity: 0.25; cursor: not-allowed; }

.bulk-action-bar .btn-bulk-clear {
  background: none;
  border: none;
  color: rgba(0,0,0,0.4);
  font-size: var(--text-xs);
  font-weight: 500;
  cursor: pointer;
  text-decoration: underline;
}

.bulk-action-bar .btn-bulk-clear:hover { color: rgba(0,0,0,0.7); }

/* Toggle button for bulk mode */
.btn-bulk-toggle {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-sm);
  font-family: var(--font-display);
  font-size: var(--text-xs);
  font-weight: 600;
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  color: var(--text-secondary);
  cursor: pointer;
  height: 28px;
  transition: all var(--duration-fast) var(--ease-out);
}

.btn-bulk-toggle:hover { border-color: #1a1a1a; color: #1a1a1a; }

.btn-bulk-toggle.active {
  background: #1a1a1a;
  color: #ffffff;
  border-color: #1a1a1a;
}

@media (max-width: 768px) {
  .bulk-action-bar {
    padding: var(--space-3) var(--space-4);
    flex-wrap: wrap;
    gap: var(--space-2);
  }
  .bulk-action-bar .bulk-count { min-width: auto; }
  .bulk-action-bar .bulk-slots { flex: none; }
}

/* --- Utility --- */
.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;
}

.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-2 { gap: var(--space-2); }
.gap-3 { gap: var(--space-3); }
.gap-4 { gap: var(--space-4); }
.gap-6 { gap: var(--space-6); }
.mt-4 { margin-top: var(--space-4); }
.mt-6 { margin-top: var(--space-6); }
.mb-4 { margin-bottom: var(--space-4); }
.mb-6 { margin-bottom: var(--space-6); }
.text-center { text-align: center; }
.text-sm { font-size: var(--text-sm); }
.text-secondary { color: var(--text-secondary); }
.hidden { display: none !important; }