/* Main Stylesheet - Math Practice Application */

/* CSS Variables for consistent theming */
:root {
  --primary-color: #2563eb;
  --primary-hover: #1d4ed8;
  --success-color: #16a34a;
  --warning-color: #ea580c;
  --danger-color: #dc2626;
  --text-primary: #1f2937;
  --text-secondary: #6b7280;
  --bg-primary: #ffffff;
  --bg-secondary: #f3f4f6;
  --border-color: #e5e7eb;
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --spacing-unit: 0.25rem;
}

/* Reset and Base Styles */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  color: var(--text-primary);
  background-color: var(--bg-secondary);
  line-height: 1.6;
  min-height: 100vh;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.2;
  margin-bottom: 1rem;
}

h1 {
  font-size: 2.25rem;
}

h2 {
  font-size: 1.875rem;
}

h3 {
  font-size: 1.5rem;
}

h4 {
  font-size: 1.25rem;
}

p {
  margin-bottom: 1rem;
}

/* Header */
.header {
  background-color: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
  padding: 1rem 2rem;
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-content {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
}

.header h1 {
  font-size: 1.5rem;
  margin: 0;
  color: var(--primary-color);
}

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

/* Container */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem;
}

.container-wide {
  max-width: 1400px;
  margin: 0 auto;
  padding: 2rem;
}

/* Card Components */
.card {
  background-color: var(--bg-primary);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  border: 1px solid var(--border-color);
}

.card-header {
  padding-bottom: 1rem;
  margin-bottom: 1rem;
  border-bottom: 1px solid var(--border-color);
}

.card-title {
  font-size: 1.25rem;
  font-weight: 600;
  margin: 0;
}

.card-body {
  padding: 0;
}

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

/* Grid System */
.grid {
  display: grid;
  gap: 1.5rem;
}

.grid-cols-1 {
  grid-template-columns: repeat(1, 1fr);
}

.grid-cols-2 {
  grid-template-columns: repeat(2, 1fr);
}

.grid-cols-3 {
  grid-template-columns: repeat(3, 1fr);
}

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

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.625rem 1.25rem;
  font-size: 1rem;
  font-weight: 500;
  line-height: 1.5;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all 0.2s ease;
  text-decoration: none;
  gap: 0.5rem;
  min-height: 44px; /* Touch-friendly minimum */
  min-width: 44px;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

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

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

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

.btn-success:hover:not(:disabled) {
  background-color: #15803d;
}

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

.btn-warning:hover:not(:disabled) {
  background-color: #c2410c;
}

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

.btn-danger:hover:not(:disabled) {
  background-color: #b91c1c;
}

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

.btn-secondary:hover:not(:disabled) {
  background-color: #e5e7eb;
}

.btn-icon {
  padding: 0.625rem;
  min-width: 44px;
  min-height: 44px;
}

.btn-sm {
  padding: 0.375rem 0.75rem;
  font-size: 0.875rem;
  min-height: 36px;
  min-width: 36px;
}

.btn-lg {
  padding: 0.875rem 1.5rem;
  font-size: 1.125rem;
  min-height: 52px;
  min-width: 52px;
}

/* Form Elements */
.form-group {
  margin-bottom: 1.5rem;
}

.form-label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 500;
  color: var(--text-primary);
}

.form-input {
  width: 100%;
  padding: 0.625rem 0.875rem;
  font-size: 1rem;
  line-height: 1.5;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
  min-height: 44px;
}

.form-input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

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

select.form-input {
  appearance: none;
  background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3e%3cpath stroke='%236b7280' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='M6 8l4 4 4-4'/%3e%3c/svg%3e");
  background-position: right 0.5rem center;
  background-repeat: no-repeat;
  background-size: 1.5em 1.5em;
  padding-right: 2.5rem;
}

/* Badge */
.badge {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  font-size: 0.875rem;
  font-weight: 500;
  line-height: 1;
  border-radius: var(--radius-sm);
}

.badge-success {
  background-color: #dcfce7;
  color: #166534;
}

.badge-warning {
  background-color: #fed7aa;
  color: #9a3412;
}

.badge-danger {
  background-color: #fee2e2;
  color: #991b1b;
}

.badge-info {
  background-color: #dbeafe;
  color: #1e40af;
}

/* Alert */
.alert {
  padding: 1rem;
  border-radius: var(--radius-md);
  margin-bottom: 1rem;
  border: 1px solid transparent;
}

.alert-success {
  background-color: #dcfce7;
  color: #166534;
  border-color: #bbf7d0;
}

.alert-warning {
  background-color: #fed7aa;
  color: #9a3412;
  border-color: #fdba74;
}

.alert-danger {
  background-color: #fee2e2;
  color: #991b1b;
  border-color: #fecaca;
}

.alert-info {
  background-color: #dbeafe;
  color: #1e40af;
  border-color: #bfdbfe;
}

/* Modal */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.5);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: 1rem;
}

.modal-overlay.active {
  display: flex;
}

.modal {
  background-color: var(--bg-primary);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  max-width: 600px;
  width: 100%;
  max-height: 90vh;
  overflow: auto;
}

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

.modal-title {
  font-size: 1.5rem;
  font-weight: 600;
  margin: 0;
}

.modal-close {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text-secondary);
  padding: 0.25rem;
  line-height: 1;
  min-width: 44px;
  min-height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
}

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

.modal-body {
  padding: 1.5rem;
}

.modal-footer {
  padding: 1.5rem;
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: flex-end;
  gap: 0.75rem;
}

/* Loading Spinner */
.spinner {
  display: inline-block;
  width: 20px;
  height: 20px;
  border: 2px solid rgba(255, 255, 255, 0.3);
  border-radius: 50%;
  border-top-color: white;
  animation: spin 0.6s linear infinite;
}

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

/* Utility Classes */
.text-center {
  text-align: center;
}

.text-right {
  text-align: right;
}

.text-left {
  text-align: left;
}

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

.text-success {
  color: var(--success-color);
}

.text-warning {
  color: var(--warning-color);
}

.text-danger {
  color: var(--danger-color);
}

.mt-1 { margin-top: calc(var(--spacing-unit) * 1); }
.mt-2 { margin-top: calc(var(--spacing-unit) * 2); }
.mt-3 { margin-top: calc(var(--spacing-unit) * 3); }
.mt-4 { margin-top: calc(var(--spacing-unit) * 4); }
.mb-1 { margin-bottom: calc(var(--spacing-unit) * 1); }
.mb-2 { margin-bottom: calc(var(--spacing-unit) * 2); }
.mb-3 { margin-bottom: calc(var(--spacing-unit) * 3); }
.mb-4 { margin-bottom: calc(var(--spacing-unit) * 4); }

.d-none {
  display: none !important;
}

.d-block {
  display: block !important;
}

.d-flex {
  display: flex !important;
}

.flex-column {
  flex-direction: column;
}

.flex-wrap {
  flex-wrap: wrap;
}

.gap-1 { gap: calc(var(--spacing-unit) * 1); }
.gap-2 { gap: calc(var(--spacing-unit) * 2); }
.gap-3 { gap: calc(var(--spacing-unit) * 3); }
.gap-4 { gap: calc(var(--spacing-unit) * 4); }

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

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

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

/* Responsive Design */
@media (max-width: 768px) {
  html {
    font-size: 14px;
  }

  .header {
    padding: 1rem;
  }

  .header-content {
    flex-direction: column;
    align-items: flex-start;
  }

  .container,
  .container-wide {
    padding: 1rem;
  }

  .grid-cols-2,
  .grid-cols-3,
  .grid-cols-4 {
    grid-template-columns: repeat(1, 1fr);
  }

  h1 {
    font-size: 1.75rem;
  }

  h2 {
    font-size: 1.5rem;
  }

  .modal {
    max-width: 100%;
    margin: 0.5rem;
  }
}

@media (min-width: 769px) and (max-width: 1024px) {
  .grid-cols-3,
  .grid-cols-4 {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* Print Styles */
@media print {
  body {
    background-color: white;
  }

  .header,
  .btn,
  .modal-overlay {
    display: none !important;
  }

  .card {
    box-shadow: none;
    border: 1px solid #000;
    page-break-inside: avoid;
  }
}