/* ========================================
           CSS VARIABLES & RESET
======================================== */
:root {
  --primary-color: #6366f1;
  --primary-dark: #4f46e5;
  --primary-light: #818cf8;
  --secondary-color: #8b5cf6;
  --success-color: #10b981;
  --warning-color: #f59e0b;
  --danger-color: #ef4444;
  --info-color: #3b82f6;

  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --bg-tertiary: #f1f5f9;

  --text-primary: #1e293b;
  --text-secondary: #64748b;
  --text-tertiary: #94a3b8;

  --border-color: #e2e8f0;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);

  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;

  --transition-fast: 150ms ease-in-out;
  --transition-base: 200ms ease-in-out;
  --transition-slow: 300ms ease-in-out;
}

[data-theme="dark"] {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-tertiary: #334155;

  --text-primary: #f1f5f9;
  --text-secondary: #cbd5e1;
  --text-tertiary: #94a3b8;

  --border-color: #334155;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.6);
}

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

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background var(--transition-base), color var(--transition-base);
}

/* ========================================
           REQUIRED FIELD ASTERISK
        ======================================== */
label .required {
  color: var(--danger-color);
  margin-left: 2px;
  font-weight: bold;
}

/* ========================================
           HEADER & NAVIGATION
        ======================================== */
.header {
  background: var(--bg-secondary);
  box-shadow: var(--shadow-md);
  position: sticky;
  top: 0;
  z-index: 100;
  transition: background var(--transition-base);
}

.header-content {
  max-width: 1400px;
  margin: 0 auto;
  padding: 1rem 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary-color);
}

.logo-icon {
  width: 40px;
  height: 40px;
  background: linear-gradient(
    135deg,
    var(--primary-color),
    var(--secondary-color)
  );
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 1.25rem;
}

.header-actions {
  display: flex;
  gap: 1rem;
  align-items: center;
}

.student-name {
  color: var(--text-secondary);
  font-size: 0.9rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.student-name strong {
  color: var(--text-primary);
  font-weight: 600;
}

.edit-name-btn {
  background: transparent;
  border: none;
  color: var(--primary-color);
  cursor: pointer;
  padding: 0.25rem;
  font-size: 0.9rem;
  transition: all var(--transition-fast);
}

.edit-name-btn:hover {
  color: var(--primary-dark);
  transform: scale(1.1);
}

.theme-toggle {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 0.5rem 0.75rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-size: 1.25rem;
}

.theme-toggle:hover {
  background: var(--primary-color);
  color: white;
  transform: scale(1.05);
}

/* ========================================
           TABS NAVIGATION
        ======================================== */
.tabs-container {
  background: var(--bg-secondary);
  border-bottom: 2px solid var(--border-color);
  position: sticky;
  top: 73px;
  z-index: 99;
}

.tabs {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 2rem;
  display: flex;
  gap: 0.5rem;
  overflow-x: auto;
  scrollbar-width: thin;
}

.tab-btn {
  background: transparent;
  border: none;
  padding: 1rem 1.5rem;
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text-secondary);
  border-bottom: 3px solid transparent;
  transition: all var(--transition-fast);
  white-space: nowrap;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.tab-btn:hover {
  color: var(--primary-color);
  background: var(--bg-tertiary);
}

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

.tab-icon {
  font-size: 1.1rem;
}

/* ========================================
           MAIN CONTAINER
        ======================================== */
.container {
  max-width: 1400px;
  margin: 2rem auto;
  padding: 0 2rem;
}

.tab-content {
  display: none;
  animation: fadeIn 0.3s ease-in-out;
}

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

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

/* ========================================
           CARDS
        ======================================== */
.card {
  background: var(--bg-secondary);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  transition: all var(--transition-base);
}

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

.card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 2px solid var(--border-color);
}

.card-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.card-title-icon {
  color: var(--primary-color);
}

/* ========================================
           STATS CARDS
        ======================================== */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.stat-card {
  background: linear-gradient(
    135deg,
    var(--primary-color),
    var(--secondary-color)
  );
  color: white;
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-md);
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}

.stat-card::before {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  width: 100px;
  height: 100px;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 50%;
  transform: translate(30%, -30%);
}

.stat-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-xl);
}

.stat-card.success {
  background: linear-gradient(135deg, #10b981, #059669);
}

.stat-card.warning {
  background: linear-gradient(135deg, #f59e0b, #d97706);
}

.stat-card.danger {
  background: linear-gradient(135deg, #ef4444, #dc2626);
}

.stat-card.info {
  background: linear-gradient(135deg, #3b82f6, #2563eb);
}

.stat-value {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: 0.25rem;
}

.stat-label {
  font-size: 0.9rem;
  opacity: 0.9;
  font-weight: 500;
}

.stat-icon {
  position: absolute;
  bottom: 1rem;
  right: 1rem;
  font-size: 3rem;
  opacity: 0.2;
}

/* ========================================
           FORM ELEMENTS
        ======================================== */
.form-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.form-group.full-width {
  grid-column: 1 / -1;
}

label {
  font-weight: 600;
  color: var(--text-primary);
  font-size: 0.9rem;
}

input[type="text"],
input[type="date"],
select,
textarea {
  padding: 0.75rem;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-family: inherit;
  transition: all var(--transition-fast);
  background: var(--bg-primary);
  color: var(--text-primary);
}

input:focus,
select:focus,
textarea:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

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

.checkbox-group {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-top: 0.5rem;
}

input[type="checkbox"] {
  width: 18px;
  height: 18px;
  cursor: pointer;
  accent-color: var(--primary-color);
}

/* ========================================
           BUTTONS
        ======================================== */
.btn {
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  justify-content: center;
  text-decoration: none;
}

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

.btn:active {
  transform: translateY(0);
}

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

.btn-primary:hover {
  background: var(--primary-dark);
}

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

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

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

.btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

.btn-sm {
  padding: 0.5rem 1rem;
  font-size: 0.875rem;
}

.btn-icon {
  padding: 0.5rem;
  width: 36px;
  height: 36px;
}

.btn-group {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
}

/* ========================================
           TABLE
        ======================================== */
.table-controls {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
  gap: 1rem;
}

.search-box {
  position: relative;
  flex: 1;
  min-width: 250px;
  max-width: 400px;
}

.search-box input {
  width: 100%;
  padding-left: 2.5rem;
}

.search-icon {
  position: absolute;
  left: 0.75rem;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-tertiary);
}

.filter-buttons {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.filter-btn {
  padding: 0.5rem 1rem;
  border: 2px solid var(--border-color);
  background: var(--bg-primary);
  border-radius: var(--radius-md);
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: all var(--transition-fast);
}

.filter-btn:hover {
  border-color: var(--primary-color);
  color: var(--primary-color);
}

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

.table-wrapper {
  overflow-x: auto;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}

thead {
  background: var(--bg-tertiary);
  position: sticky;
  top: 0;
}

th {
  padding: 1rem;
  text-align: left;
  font-weight: 600;
  color: var(--text-primary);
  border-bottom: 2px solid var(--border-color);
  white-space: nowrap;
  cursor: pointer;
  user-select: none;
}

th:hover {
  background: var(--primary-color);
  color: white;
}

th.sortable::after {
  content: " \f0dc";
  font-family: "Font Awesome 6 Free";
  font-weight: 900;
  opacity: 0.3;
  margin-left: 0.5rem;
}

th.sort-asc::after {
  content: " \f0de";
  opacity: 1;
}

th.sort-desc::after {
  content: " \f0dd";
  opacity: 1;
}

td {
  padding: 1rem;
  border-bottom: 1px solid var(--border-color);
}

tbody tr {
  transition: background var(--transition-fast);
}

tbody tr:hover {
  background: var(--bg-tertiary);
}

.badge {
  display: inline-block;
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
}

.badge-not-started {
  background: #fee2e2;
  color: #991b1b;
}

.badge-pending {
  background: #fef3c7;
  color: #92400e;
}

.badge-completed {
  background: #d1fae5;
  color: #065f46;
}

[data-theme="dark"] .badge-not-started {
  background: #7f1d1d;
  color: #fca5a5;
}

[data-theme="dark"] .badge-pending {
  background: #78350f;
  color: #fcd34d;
}

[data-theme="dark"] .badge-completed {
  background: #064e3b;
  color: #6ee7b7;
}

.days-left {
  font-weight: 600;
}

.days-left.overdue {
  color: var(--danger-color);
}

.days-left.today {
  color: var(--warning-color);
}

.days-left.upcoming {
  color: var(--info-color);
}

.days-left.future {
  color: var(--success-color);
}

.no-deadline {
  color: var(--text-tertiary);
  font-style: italic;
}

/* ========================================
           ACTION BUTTONS IN TABLE
        ======================================== */
.action-buttons {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

/* ========================================
           SUBJECTS & WORK TYPES LIST
        ======================================== */
.list-item {
  background: var(--bg-tertiary);
  padding: 1rem;
  border-radius: var(--radius-md);
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.75rem;
  transition: all var(--transition-fast);
}

.list-item:hover {
  background: var(--primary-color);
  color: white;
  transform: translateX(5px);
}

.list-item-content {
  flex: 1;
}

.list-item-title {
  font-weight: 600;
  font-size: 1rem;
  margin-bottom: 0.25rem;
}

.list-item-subtitle {
  font-size: 0.875rem;
  opacity: 0.8;
}

.list-item-actions {
  display: flex;
  gap: 0.5rem;
}

.empty-state {
  text-align: center;
  padding: 3rem 1rem;
  color: var(--text-tertiary);
}

.empty-state-icon {
  font-size: 4rem;
  margin-bottom: 1rem;
}

.empty-state-text {
  font-size: 1.1rem;
  margin-bottom: 0.5rem;
}

/* ========================================
           MODAL
        ======================================== */
.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.6);
  z-index: 1000;
  align-items: center;
  justify-content: center;
  animation: fadeIn 0.2s ease-in-out;
}

.modal.active {
  display: flex;
}

.modal-content {
  background: var(--bg-secondary);
  border-radius: var(--radius-xl);
  padding: 2rem;
  max-width: 500px;
  width: 90%;
  max-height: 90vh;
  overflow-y: auto;
  box-shadow: var(--shadow-xl);
  animation: slideUp 0.3s ease-out;
}

@keyframes slideUp {
  from {
    transform: translateY(50px);
    opacity: 0;
  }
  to {
    transform: translateY(0);
    opacity: 1;
  }
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 2px solid var(--border-color);
}

.modal-title {
  font-size: 1.5rem;
  font-weight: 700;
}

.modal-close {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

.modal-close:hover {
  color: var(--danger-color);
}

.modal-body {
  margin-bottom: 1.5rem;
}

.modal-footer {
  display: flex;
  gap: 1rem;
  justify-content: flex-end;
}

/* ========================================
           TOAST NOTIFICATIONS
        ======================================== */
.toast-container {
  position: fixed;
  top: 90px;
  right: 20px;
  z-index: 2000;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.toast {
  background: var(--bg-secondary);
  border-left: 4px solid var(--primary-color);
  border-radius: var(--radius-md);
  padding: 1rem 1.5rem;
  box-shadow: var(--shadow-lg);
  min-width: 300px;
  max-width: 400px;
  display: flex;
  align-items: center;
  gap: 1rem;
  animation: slideInRight 0.3s ease-out;
}

@keyframes slideInRight {
  from {
    transform: translateX(400px);
    opacity: 0;
  }
  to {
    transform: translateX(0);
    opacity: 1;
  }
}

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

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

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

.toast.info {
  border-left-color: var(--info-color);
}

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

.toast.success .toast-icon {
  color: var(--success-color);
}

.toast.error .toast-icon {
  color: var(--danger-color);
}

.toast.warning .toast-icon {
  color: var(--warning-color);
}

.toast.info .toast-icon {
  color: var(--info-color);
}

.toast-content {
  flex: 1;
}

.toast-title {
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.toast-message {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

/* ========================================
           CHARTS
        ======================================== */
.charts-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}

.chart-card {
  background: var(--bg-secondary);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-md);
}

.chart-title {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 1rem;
  color: var(--text-primary);
}

.chart-container {
  position: relative;
  height: 300px;
}

/* ========================================
           INSIGHTS SECTION
        ======================================== */
.insights-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}

.insight-card {
  background: var(--bg-secondary);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-md);
  border-left: 4px solid var(--primary-color);
}

.insight-icon {
  font-size: 2rem;
  margin-bottom: 1rem;
}

.insight-title {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.insight-text {
  color: var(--text-secondary);
  font-size: 0.9rem;
  line-height: 1.6;
}

/* ========================================
           MOTIVATIONAL QUOTE
        ======================================== */
.quote-card {
  background: linear-gradient(
    135deg,
    var(--primary-color),
    var(--secondary-color)
  );
  border-radius: var(--radius-lg);
  padding: 2rem;
  margin-top: 2rem;
  color: white;
  box-shadow: var(--shadow-lg);
  position: relative;
  overflow: hidden;
}

.quote-card::before {
  content: "\f10d";
  font-family: "Font Awesome 6 Free";
  font-weight: 900;
  position: absolute;
  top: 1rem;
  left: 1rem;
  font-size: 3rem;
  opacity: 0.2;
}

.quote-text {
  font-size: 1.2rem;
  font-style: italic;
  margin-bottom: 1rem;
  line-height: 1.8;
  position: relative;
  z-index: 1;
}

.quote-author {
  text-align: right;
  font-weight: 600;
  font-size: 1rem;
  opacity: 0.9;
  position: relative;
  z-index: 1;
}

.quote-author::before {
  content: "— ";
}

/* ========================================
           WELCOME MODAL
        ======================================== */
.welcome-modal .modal-content {
  text-align: center;
}

.welcome-icon {
  font-size: 4rem;
  color: var(--primary-color);
  margin-bottom: 1rem;
}

.welcome-text {
  font-size: 1.1rem;
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
}

/* ========================================
           RESPONSIVE DESIGN
        ======================================== */
@media (max-width: 768px) {
  .header-content {
    padding: 1rem;
  }

  .logo {
    font-size: 1.25rem;
  }

  .container {
    padding: 0 1rem;
  }

  .tabs {
    padding: 0 1rem;
  }

  .tab-btn {
    padding: 0.75rem 1rem;
    font-size: 0.85rem;
  }

  .stats-grid {
    grid-template-columns: 1fr;
  }

  .form-grid {
    grid-template-columns: 1fr;
  }

  .table-controls {
    flex-direction: column;
    align-items: stretch;
  }

  .search-box {
    max-width: 100%;
  }

  .filter-buttons {
    justify-content: center;
  }

  table {
    font-size: 0.8rem;
  }

  th,
  td {
    padding: 0.5rem;
  }

  .card {
    padding: 1rem;
  }

  .modal-content {
    padding: 1.5rem;
  }

  .toast-container {
    left: 10px;
    right: 10px;
  }

  .toast {
    min-width: auto;
  }

  .charts-grid {
    grid-template-columns: 1fr;
  }
}

/* ========================================
           UTILITY CLASSES
        ======================================== */
.text-center {
  text-align: center;
}

.mt-1 {
  margin-top: 0.5rem;
}
.mt-2 {
  margin-top: 1rem;
}
.mt-3 {
  margin-top: 1.5rem;
}
.mt-4 {
  margin-top: 2rem;
}

.mb-1 {
  margin-bottom: 0.5rem;
}
.mb-2 {
  margin-bottom: 1rem;
}
.mb-3 {
  margin-bottom: 1.5rem;
}
.mb-4 {
  margin-bottom: 2rem;
}

.hidden {
  display: none !important;
}

.text-muted {
  color: var(--text-secondary);
}

.text-small {
  font-size: 0.875rem;
}

.fw-bold {
  font-weight: 700;
}

.d-flex {
  display: flex;
}

.justify-between {
  justify-content: space-between;
}

.align-center {
  align-items: center;
}

.gap-1 {
  gap: 0.5rem;
}
.gap-2 {
  gap: 1rem;
}
.gap-3 {
  gap: 1.5rem;
}
.gap-4 {
  gap: 2rem;
}