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

:root {
  --primary: #1a5276;
  --primary-light: #2980b9;
  --accent: #27ae60;
  --accent-dark: #1e8449;
  --danger: #c0392b;
  --danger-light: #e74c3c;
  --warning: #f39c12;
  --bg: #f0f4f8;
  --card-bg: #ffffff;
  --text: #2c3e50;
  --text-light: #7f8c8d;
  --border: #dce1e6;
  --radius: 10px;
  --shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
}

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

.container {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 20px;
}

header {
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
  color: #fff;
  padding: 20px 0;
}

.header-row {
  display: flex;
  align-items: center;
  gap: 20px;
  justify-content: flex-start;
  max-width: 860px;
  margin: 0 auto;
  padding: 0 20px;
}

.header-logo {
  height: 60px;
  width: auto;
  border-radius: 8px;
  flex-shrink: 0;
}

.header-text {
  text-align: left;
  border-left: 1px solid rgba(255, 255, 255, 0.3);
  padding-left: 20px;
}

header h1 {
  font-size: 1.6rem;
  font-weight: 700;
  margin-bottom: 2px;
  line-height: 1.2;
}

header .subtitle {
  font-size: 0.88rem;
  opacity: 0.8;
  font-weight: 400;
}

.card {
  background: var(--card-bg);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 28px;
  margin-top: 24px;
}

.method-tabs {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-top: 12px;
}

.tab {
  padding: 10px 18px;
  border: 2px solid var(--border);
  border-radius: 6px;
  background: var(--card-bg);
  color: var(--text);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}

.tab:hover {
  border-color: var(--primary-light);
  color: var(--primary);
}

.tab.active {
  border-color: var(--primary);
  background: var(--primary);
  color: #fff;
}

.method-panel {
  display: none;
}

.method-panel.active {
  display: block;
}

.method-desc {
  color: var(--text-light);
  font-size: 0.92rem;
  margin-bottom: 20px;
}

.warning-desc {
  color: var(--danger);
  font-weight: 500;
  background: #fdf2f2;
  padding: 10px 14px;
  border-radius: 6px;
  border-left: 4px solid var(--danger);
}

.form-row {
  display: flex;
  gap: 20px;
  margin-bottom: 16px;
}

.form-group {
  flex: 1;
}

.form-group label {
  display: block;
  font-size: 0.88rem;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text);
}

.form-group .optional {
  font-weight: 400;
  color: var(--text-light);
  font-size: 0.8rem;
}

.form-group input {
  width: 100%;
  padding: 10px 14px;
  border: 2px solid var(--border);
  border-radius: 6px;
  font-size: 1rem;
  color: var(--text);
  transition: border-color 0.2s;
}

.form-group input:focus {
  outline: none;
  border-color: var(--primary-light);
}

.form-group input::placeholder {
  color: #bdc3c7;
}

.form-group small {
  display: block;
  margin-top: 4px;
  font-size: 0.78rem;
  color: var(--text-light);
}

.btn-row {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-top: 8px;
}

.btn-calculate {
  display: inline-block;
  padding: 12px 32px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 6px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
}

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

.btn-reset {
  display: inline-block;
  padding: 12px 24px;
  background: transparent;
  color: var(--text-light);
  border: 2px solid var(--border);
  border-radius: 6px;
  font-size: 0.92rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}

.btn-reset:hover {
  background: var(--danger);
  color: #fff;
  border-color: var(--danger);
}

.btn-secondary {
  display: inline-block;
  padding: 8px 20px;
  background: var(--card-bg);
  color: var(--primary);
  border: 2px solid var(--primary);
  border-radius: 6px;
  font-size: 0.88rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
  margin-right: 8px;
}

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

.btn-copy {
  float: right;
  padding: 6px 14px;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 4px;
  font-size: 0.82rem;
  color: var(--text-light);
  cursor: pointer;
  transition: all 0.2s;
}

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

.results-card {
  border-top: 4px solid var(--accent);
}

.result-primary {
  text-align: center;
  padding: 20px 0;
  border-bottom: 1px solid var(--border);
  margin-bottom: 20px;
}

.result-label {
  font-size: 0.9rem;
  color: var(--text-light);
  margin-bottom: 4px;
}

.result-value {
  font-size: 2.4rem;
  font-weight: 700;
  color: var(--primary);
}

.result-row {
  display: flex;
  gap: 20px;
  margin-bottom: 20px;
}

.result-item {
  flex: 1;
  text-align: center;
  padding: 16px;
  background: var(--bg);
  border-radius: 8px;
}

.result-item.full-width {
  flex: 1;
}

.result-value-sm {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  margin-top: 4px;
}

.result-value-sm.highlight {
  color: var(--accent-dark);
}

.recommendation {
  margin: 24px 0;
}

.recommendation h3 {
  font-size: 1rem;
  margin-bottom: 12px;
}

.graft-options {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.graft-option {
  padding: 14px 20px;
  border: 2px solid var(--border);
  border-radius: 8px;
  text-align: center;
  min-width: 120px;
  transition: all 0.2s;
}

.graft-option.recommended {
  border-color: var(--accent);
  background: #eafaf1;
}

.graft-option.recommended .graft-badge {
  display: inline-block;
  background: var(--accent);
  color: #fff;
  font-size: 0.7rem;
  font-weight: 600;
  padding: 2px 8px;
  border-radius: 10px;
  margin-bottom: 6px;
  text-transform: uppercase;
}

.graft-option .graft-size {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text);
}

.graft-option .graft-area {
  font-size: 0.82rem;
  color: var(--text-light);
  margin-top: 2px;
}

.graft-option .graft-waste {
  font-size: 0.78rem;
  color: var(--warning);
  margin-top: 4px;
  font-weight: 500;
}

.graft-option.too-small {
  opacity: 0.4;
  border-style: dashed;
}

.comparison-box {
  margin: 24px 0;
  padding: 20px;
  background: #fdf2f2;
  border-radius: 8px;
  border-left: 4px solid var(--danger);
}

.comparison-box h3 {
  font-size: 1rem;
  margin-bottom: 12px;
  color: var(--danger);
}

.comparison-grid {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  margin-bottom: 12px;
}

.comp-item {
  flex: 1;
  min-width: 140px;
  text-align: center;
}

.comp-label {
  font-size: 0.82rem;
  color: var(--text-light);
  margin-bottom: 4px;
}

.comp-value {
  font-size: 1.3rem;
  font-weight: 700;
}

.comp-value.danger {
  color: var(--danger);
}

.warning-text {
  font-size: 0.85rem;
  color: var(--text-light);
  font-style: italic;
}

.doc-template {
  margin-top: 24px;
  border-top: 1px solid var(--border);
  padding-top: 20px;
}

.doc-template h3 {
  font-size: 1rem;
  margin-bottom: 12px;
}

.doc-template pre {
  background: #f8f9fa;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 16px;
  font-size: 0.84rem;
  line-height: 1.7;
  overflow-x: auto;
  white-space: pre-wrap;
  color: var(--text);
}

.steps {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin: 20px 0;
}

.step {
  display: flex;
  gap: 14px;
  align-items: flex-start;
}

.step-number {
  flex-shrink: 0;
  width: 36px;
  height: 36px;
  background: var(--primary);
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.95rem;
}

.step-content h3 {
  font-size: 0.95rem;
  margin-bottom: 4px;
}

.step-content p {
  font-size: 0.85rem;
  color: var(--text-light);
}

.formula-box {
  background: var(--bg);
  border-radius: 8px;
  padding: 20px;
  text-align: center;
  margin-top: 20px;
}

.formula-box h3 {
  font-size: 0.9rem;
  color: var(--text-light);
  margin-bottom: 10px;
}

.formula {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--primary);
  font-family: "Georgia", serif;
}

.formula-box p {
  font-size: 0.82rem;
  color: var(--text-light);
  margin-top: 8px;
}

footer {
  margin-top: 40px;
  padding: 28px 0;
  background: var(--primary);
  color: rgba(255, 255, 255, 0.8);
  text-align: center;
  font-size: 0.84rem;
}

footer p {
  margin-bottom: 6px;
}

footer .disclaimer {
  font-size: 0.78rem;
  opacity: 0.65;
  max-width: 600px;
  margin: 0 auto 6px;
}

footer .references a {
  color: rgba(255, 255, 255, 0.9);
}

.history-entry {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 0;
  border-bottom: 1px solid var(--border);
  font-size: 0.88rem;
}

.history-entry:last-child {
  border-bottom: none;
}

.history-meta {
  color: var(--text-light);
  font-size: 0.8rem;
}

@media (max-width: 640px) {
  .header-row { flex-direction: column; text-align: center; }
  .header-text { text-align: center; }
  header h1 { font-size: 1.3rem; }
  .method-tabs { flex-direction: column; }
  .tab { text-align: center; }
  .form-row { flex-direction: column; gap: 12px; }
  .result-row { flex-direction: column; }
  .comparison-grid { flex-direction: column; }
  .steps { grid-template-columns: 1fr; }
  .graft-options { flex-direction: column; }
  .graft-option { min-width: unset; }
  .btn-row { flex-direction: column; }
}