:root {
  --bg-color: #f8f9fa;
  --card-bg: #ffffff;
  --text-primary: #212529;
  --text-secondary: #6c757d;
  --text-tertiary: #adb5bd;
  --border-color: #dee2e6;
  --border-color-light: #e9ecef;
  --primary-color: #007bff;
  --primary-color-dark: #0056b3;
  --primary-color-light: #e6f2ff;
  --success-bg: #d4edda;
  --success-text: #155724;
  --error-bg: #f8d7da;
  --error-text: #721c24;
  --shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
  --shadow-hover: 0 6px 16px rgba(0, 0, 0, 0.08);
  --border-radius: 12px;
  --transition-speed: 0.3s;
}

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

body {
  font-family: 'Inter', 'PingFang TC', 'Microsoft JhengHei', sans-serif;
  background: var(--bg-color);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* === Container === */
.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 32px 20px 64px;
}

/* === Header === */
header {
  text-align: center;
  margin-bottom: 40px;
}

header h1 {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.02em;
}

.subtitle {
  color: var(--text-secondary);
  margin-top: 8px;
  font-size: 1rem;
}

/* === Card === */
.card {
  background: var(--card-bg);
  border-radius: var(--border-radius);
  padding: 28px;
  margin-bottom: 24px;
  box-shadow: var(--shadow);
  transition: box-shadow var(--transition-speed) ease;
}

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

.card h2 {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 24px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border-color-light);
  display: flex;
  align-items: center;
  gap: 8px;
}

/* === Form Layout === */
.form-row {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 20px;
  margin-bottom: 20px;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.form-group label {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
}

.form-group input,
.form-group select {
  padding: 10px 14px;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  font-size: 0.95rem;
  color: var(--text-primary);
  background: var(--bg-color);
  transition: border-color var(--transition-speed), box-shadow var(--transition-speed);
  width: 100%;
  font-family: inherit;
}

.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px var(--primary-color-light);
  background: var(--card-bg);
}

/* === Buttons === */
.action-row {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  margin-top: 12px;
  align-items: center;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 24px;
  border: none;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-speed) ease;
  text-decoration: none;
}

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

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

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

.btn-primary:hover:not(:disabled) {
  background: var(--primary-color-dark);
  box-shadow: 0 2px 8px rgba(0, 123, 255, 0.3);
}

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

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

.btn-sm {
  padding: 8px 16px;
  font-size: 0.875rem;
}

/* === Spinner === */
.spinner {
  width: 18px;
  height: 18px;
  border: 2.5px solid rgba(255, 255, 255, 0.3);
  border-top-color: #fff;
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  display: inline-block;
}

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

.hidden {
  display: none !important;
}

/* === Status Message === */
.status-message {
  margin-top: 20px;
  padding: 14px 18px;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 500;
  animation: fadeIn 0.5s ease;
}

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

.status-message.success {
  background: var(--success-bg);
  color: var(--success-text);
}

.status-message.error {
  background: var(--error-bg);
  color: var(--error-text);
}

/* === History Section === */
.history-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

.chart-container {
  margin-bottom: 28px;
  padding: 20px;
  background: linear-gradient(135deg, #fcfdff 0%, #f7f9fc 100%);
  border-radius: 10px;
  border: 1px solid var(--border-color-light);
}

.chart-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 16px;
  margin-bottom: 20px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--border-color-light);
}

.chart-controls label {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.9rem;
  cursor: pointer;
  padding: 6px 10px;
  border-radius: 6px;
  transition: background-color var(--transition-speed);
}

.chart-controls label:hover {
  background-color: var(--primary-color-light);
}

.chart-controls input[type="checkbox"] {
  accent-color: var(--primary-color);
}

.history-table-wrapper {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

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

.history-table-wrapper th,
.history-table-wrapper td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border-color-light);
  white-space: nowrap;
}

.history-table-wrapper th {
  font-weight: 600;
  background: var(--bg-color);
  color: var(--text-secondary);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.history-table-wrapper tr:last-child td {
  border-bottom: none;
}

.history-table-wrapper tr:hover td {
  background: var(--primary-color-light);
}

/* Make note column wider */
.history-table-wrapper td:last-child,
.history-table-wrapper th:last-child {
  white-space: normal;
  min-width: 250px;
}

.empty-hint {
  text-align: center;
  color: var(--text-tertiary);
  padding: 32px;
  font-size: 1rem;
}

/* Responsive Design */
@media (max-width: 768px) {
  .container {
    padding: 24px 16px 48px;
  }
  .card {
    padding: 20px;
  }
  header h1 {
    font-size: 2rem;
  }
  .form-row {
    grid-template-columns: 1fr;
  }
}

  white-space: nowrap;
}

tbody tr {
  border-bottom: 1px solid #edf2f7;
  transition: background 0.15s;
}

tbody tr:hover {
  background: #f7fafc;
}

tbody td {
  padding: 7px 10px;
  text-align: center;
  color: #4a5568;
}

tbody tr:last-child {
  border-bottom: none;
}

/* === Responsive === */
@media (max-width: 600px) {
  header h1 {
    font-size: 1.5rem;
  }

  .card {
    padding: 16px;
  }

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

  .btn {
    font-size: 0.88rem;
    padding: 9px 16px;
  }
}

@media (max-width: 400px) {
  .form-row {
    grid-template-columns: 1fr;
  }
}