/* DES Simulator Styles */
:root {
  --bg-primary: #0f1419;
  --bg-secondary: #1a2332;
  --bg-card: #1e2a3a;
  --bg-input: #141c28;
  --accent: #3b82f6;
  --accent-hover: #2563eb;
  --accent-light: #60a5fa;
  --success: #22c55e;
  --danger: #ef4444;
  --warning: #f59e0b;
  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --border: #2d3f56;
  --border-light: #3d5270;
  --mono-bg: #0d1117;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.4);
  --radius: 10px;
  --radius-sm: 6px;
}

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

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

.header {
  background: linear-gradient(135deg, var(--bg-secondary) 0%, #152030 100%);
  border-bottom: 1px solid var(--border);
  padding: 1.5rem 2rem;
}

.header-inner {
  max-width: 1400px;
  margin: 0 auto;
}

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

.logo-icon {
  font-size: 2.5rem;
}

.header h1 {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.subtitle {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-top: 0.25rem;
}

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

.panel {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem 2rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow);
}

.panel h2 {
  font-size: 1.25rem;
  margin-bottom: 0.5rem;
  color: var(--accent-light);
  border-bottom: 2px solid var(--border);
  padding-bottom: 0.75rem;
}

.section-desc {
  color: var(--text-muted);
  font-size: 0.875rem;
  margin-bottom: 1.25rem;
}

.form-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-bottom: 1.5rem;
}

.form-group label {
  display: block;
  font-weight: 600;
  margin-bottom: 0.5rem;
  font-size: 0.9rem;
}

.form-group input {
  width: 100%;
  padding: 0.75rem 1rem;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: 'Cascadia Code', 'Consolas', monospace;
  font-size: 0.95rem;
  transition: border-color 0.2s;
}

.form-group input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

.hint {
  display: block;
  color: var(--text-muted);
  font-size: 0.8rem;
  margin-top: 0.35rem;
}

.form-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
}

.mode-fieldset {
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.75rem 1.25rem;
}

.mode-fieldset legend {
  padding: 0 0.5rem;
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.radio-label {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  margin-right: 1.5rem;
  cursor: pointer;
  font-size: 0.95rem;
}

.radio-label input[type="radio"] {
  accent-color: var(--accent);
  width: 1rem;
  height: 1rem;
}

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

.btn {
  padding: 0.65rem 1.5rem;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: all 0.2s;
}

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

.btn-primary:hover {
  background: var(--accent-hover);
  transform: translateY(-1px);
}

.btn-secondary {
  background: #6366f1;
  color: white;
}

.btn-secondary:hover {
  background: #4f46e5;
}

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

.btn-outline:hover {
  border-color: var(--text-secondary);
  color: var(--text-primary);
}

.error-box {
  display: none;
  margin-top: 1rem;
  padding: 0.75rem 1rem;
  background: rgba(239, 68, 68, 0.15);
  border: 1px solid var(--danger);
  border-radius: var(--radius-sm);
  color: #fca5a5;
  font-size: 0.9rem;
}

.error-box.visible {
  display: block;
}

.result-section {
  display: none;
}

.result-section.visible {
  display: block;
}

.output-grid {
  display: grid;
  grid-template-columns: 2fr 1fr;
  gap: 1.5rem;
}

.output-item label {
  display: block;
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
  font-weight: 600;
}

.output-value {
  background: var(--mono-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 1rem;
  font-size: 0.9rem;
  word-break: break-all;
}

.output-value.hex {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--success);
  letter-spacing: 0.05em;
}

.mono {
  font-family: 'Cascadia Code', 'Consolas', monospace;
  font-size: 0.85rem;
  word-break: break-all;
}

.tabs-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}

.steps-container {
  max-height: 800px;
  overflow-y: auto;
  padding-right: 0.5rem;
}

.steps-container::-webkit-scrollbar {
  width: 6px;
}

.steps-container::-webkit-scrollbar-track {
  background: var(--bg-input);
  border-radius: 3px;
}

.steps-container::-webkit-scrollbar-thumb {
  background: var(--border-light);
  border-radius: 3px;
}

.step-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 1rem 1.25rem;
  margin-bottom: 1rem;
}

.step-card h4 {
  color: var(--accent-light);
  font-size: 0.95rem;
  margin-bottom: 0.75rem;
}

.step-card h5 {
  color: var(--text-secondary);
  font-size: 0.85rem;
  margin: 0.75rem 0 0.35rem;
}

.data-row {
  margin-bottom: 0.4rem;
  font-size: 0.85rem;
}

.data-row label {
  color: var(--text-muted);
  font-weight: 600;
  margin-right: 0.5rem;
}

.data-row.highlight {
  background: rgba(34, 197, 94, 0.1);
  border: 1px solid rgba(34, 197, 94, 0.3);
  border-radius: var(--radius-sm);
  padding: 0.5rem 0.75rem;
  margin-top: 0.5rem;
}

.schedule-table,
.sbox-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.8rem;
  margin-top: 0.5rem;
}

.schedule-table th,
.sbox-table th {
  background: var(--bg-input);
  color: var(--text-secondary);
  padding: 0.5rem 0.75rem;
  text-align: left;
  font-weight: 600;
  border-bottom: 2px solid var(--border);
  position: sticky;
  top: 0;
}

.schedule-table td,
.sbox-table td {
  padding: 0.4rem 0.75rem;
  border-bottom: 1px solid var(--border);
  vertical-align: top;
}

.schedule-table tbody tr:hover,
.sbox-table tbody tr:hover {
  background: rgba(59, 130, 246, 0.08);
}

.round-detail {
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  margin-bottom: 0.75rem;
  overflow: hidden;
}

.round-detail summary {
  padding: 0.75rem 1rem;
  cursor: pointer;
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--text-primary);
  background: rgba(59, 130, 246, 0.1);
  user-select: none;
}

.round-detail summary:hover {
  background: rgba(59, 130, 246, 0.18);
}

.round-body {
  padding: 1rem 1.25rem;
  border-top: 1px solid var(--border);
}

.swap-note {
  color: var(--text-muted);
  font-size: 0.8rem;
  font-style: italic;
  margin-top: 0.5rem;
}

.sbox-container {
  overflow-x: auto;
  margin: 0.5rem 0;
}

.roundtrip-box {
  margin-top: 1.25rem;
  padding: 1rem 1.25rem;
  border-radius: var(--radius-sm);
  border: 1px solid;
}

.roundtrip-box.success {
  background: rgba(34, 197, 94, 0.1);
  border-color: var(--success);
}

.roundtrip-box.fail {
  background: rgba(239, 68, 68, 0.1);
  border-color: var(--danger);
}

.roundtrip-box h4 {
  margin-bottom: 0.75rem;
}

.roundtrip-box.success h4 {
  color: var(--success);
}

.roundtrip-box.fail h4 {
  color: var(--danger);
}

/* ── Formula & Learning ── */
.learning-panel {
  border-color: rgba(59, 130, 246, 0.35);
  background: linear-gradient(135deg, var(--bg-card) 0%, rgba(30, 42, 58, 0.95) 100%);
}

.formula-card {
  background: rgba(13, 17, 23, 0.6);
  border: 1px solid rgba(96, 165, 250, 0.25);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius-sm);
  margin-bottom: 1rem;
  overflow: hidden;
}

.formula-card.mode-info {
  border-left-color: var(--warning);
}

.formula-card-header {
  padding: 0.5rem 0.85rem;
  background: rgba(59, 130, 246, 0.12);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent-light);
}

.formula-card-body {
  padding: 0.75rem 0.85rem;
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.65;
}

.formula-card-body p {
  margin-bottom: 0.5rem;
}

.formula-card-body ol,
.formula-card-body ul {
  margin: 0.4rem 0 0.4rem 1.25rem;
}

.formula-block {
  background: var(--mono-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.65rem 0.85rem;
  margin: 0.5rem 0;
}

.formula-block code {
  display: inline-block;
  font-family: 'Cascadia Code', 'Consolas', monospace;
  font-size: 0.9rem;
  color: #fde68a;
  margin: 0.15rem 0;
}

.formula-label {
  display: block;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--accent-light);
  margin-bottom: 0.35rem;
}

.formula-note {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-style: italic;
  margin-top: 0.35rem;
}

.formula-rules {
  list-style: disc;
  margin-left: 1.25rem;
  font-size: 0.85rem;
}

.formula-rules li {
  margin-bottom: 0.25rem;
}

.formula-instance {
  background: rgba(59, 130, 246, 0.08);
  border: 1px dashed rgba(96, 165, 250, 0.3);
  border-radius: var(--radius-sm);
  padding: 0.6rem 0.85rem;
  margin: 0.65rem 0;
  font-size: 0.85rem;
}

.formula-instance code {
  font-family: 'Cascadia Code', 'Consolas', monospace;
  color: #fde68a;
  font-size: 0.88rem;
}

.shift-table-wrap code {
  display: block;
  margin: 0.35rem 0;
  font-family: 'Cascadia Code', 'Consolas', monospace;
  color: #86efac;
  font-size: 0.85rem;
}

.sbox-formulas-list {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.5rem;
  margin: 0.75rem 0;
}

.sbox-formula-item {
  background: var(--mono-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.55rem 0.75rem;
  font-size: 0.8rem;
}

.sbox-formula-item strong {
  color: var(--accent-light);
}

.sbox-calc {
  color: var(--text-secondary);
  font-family: 'Cascadia Code', 'Consolas', monospace;
  font-size: 0.78rem;
  margin-top: 0.2rem;
}

.sbox-calc strong {
  color: var(--success);
}

.calc-cell {
  font-family: 'Cascadia Code', 'Consolas', monospace;
  font-size: 0.78rem;
  color: #fde68a;
}

.round-body h5 {
  color: var(--warning);
  font-size: 0.88rem;
  margin: 1rem 0 0.4rem;
  padding-bottom: 0.25rem;
  border-bottom: 1px solid var(--border);
}

.round-body h5:first-of-type {
  margin-top: 0.5rem;
}

.footer {
  text-align: center;
  padding: 1.5rem;
  color: var(--text-muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--border);
  margin-top: 2rem;
}

@media (min-width: 1280px) {
  .container {
    padding: 2rem 3rem;
  }

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

  .tabs-layout {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 1279px) {
  .form-grid,
  .tabs-layout,
  .output-grid,
  .sbox-formulas-list {
    grid-template-columns: 1fr;
  }

  .form-row {
    flex-direction: column;
    align-items: stretch;
  }

  .btn-group {
    justify-content: stretch;
  }

  .btn-group .btn {
    flex: 1;
  }
}

@media (max-width: 768px) {
  .header h1 {
    font-size: 1.35rem;
  }

  .container {
    padding: 1rem;
  }

  .panel {
    padding: 1rem 1.25rem;
  }
}