:root {
  --bg:             #060912;
  --bg-grid:        rgba(255,255,255,0.025);

  --surface:        rgba(255, 255, 255, 0.04);
  --surface-md:     rgba(255, 255, 255, 0.07);
  --surface-hi:     rgba(255, 255, 255, 0.11);
  --border:         rgba(255, 255, 255, 0.07);
  --border-bright:  rgba(255, 255, 255, 0.18);

  --text:           #eef2ff;
  --text-sub:       #7c8db5;
  --text-dim:       #3d4d6a;

  --c1:             #22d3ee;
  --c1-fill:        rgba(34,211,238,0.38);
  --c1-glow:        rgba(34,211,238,0.25);
  --c1-stroke:      rgba(34,211,238,0.9);

  --c2:             #fb923c;
  --c2-fill:        rgba(251,146,60,0.38);
  --c2-glow:        rgba(251,146,60,0.25);
  --c2-stroke:      rgba(251,146,60,0.9);

  --r:              18px;
  --r-sm:           10px;
  --shadow:         0 16px 48px rgba(0,0,0,0.5), 0 4px 12px rgba(0,0,0,0.3);

  font-family: 'Outfit', sans-serif;
  color-scheme: dark;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
[hidden] { display: none !important; }

body {
  background-color: var(--bg);
  background-image:
    radial-gradient(ellipse 80% 60% at 15% 10%,  rgba(99,102,241,0.09) 0%, transparent 60%),
    radial-gradient(ellipse 70% 50% at 85% 85%,  rgba(6,182,212,0.07) 0%, transparent 55%),
    radial-gradient(ellipse 60% 40% at 50% 50%,  rgba(251,146,60,0.04) 0%, transparent 60%);
  color: var(--text);
  min-height: 100vh;
  overflow-x: hidden;
}

body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(var(--bg-grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--bg-grid) 1px, transparent 1px);
  background-size: 40px 40px;
  pointer-events: none;
  z-index: 0;
}

#app { position: relative; z-index: 1; }

#main-header {
  padding: 20px 32px;
  background: rgba(6,9,18,0.7);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 20;
}

.header-brand {
  display: flex;
  align-items: center;
  gap: 16px;
  max-width: 1140px;
  margin: 0 auto;
}

.header-icon {
  font-size: 38px;
  filter: drop-shadow(0 0 14px rgba(34,211,238,0.55));
  flex-shrink: 0;
  animation: float 3s ease-in-out infinite;
}

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50%       { transform: translateY(-5px); }
}

h1 {
  font-size: clamp(1.2rem, 2.5vw, 1.65rem);
  font-weight: 800;
  background: linear-gradient(100deg, var(--c1) 0%, #a78bfa 50%, var(--c2) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1.2;
}

.header-sub {
  font-size: 0.78rem;
  color: var(--text-sub);
  font-weight: 400;
  margin-top: 3px;
  letter-spacing: 0.01em;
}

#main-content {
  max-width: 1140px;
  margin: 0 auto;
  padding: 36px 20px 40px;
  display: flex;
  flex-direction: column;
  gap: 28px;
}

#panels-container {
  display: grid;
  grid-template-columns: 1fr 48px 1fr;
  gap: 0 16px;
  align-items: start;
}

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 26px 24px;
  backdrop-filter: blur(24px);
  -webkit-backdrop-filter: blur(24px);
  box-shadow: var(--shadow);
  transition: border-color 0.3s, box-shadow 0.3s;
}

.panel:hover {
  border-color: var(--border-bright);
}

#foot-panel-1:hover { box-shadow: var(--shadow), 0 0 40px var(--c1-glow); }
#foot-panel-2:hover { box-shadow: var(--shadow), 0 0 40px var(--c2-glow); }

.panel-title {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  margin-bottom: 22px;
}

.panel-title h2 {
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.dot, .legend-dot {
  width: 11px;
  height: 11px;
  border-radius: 50%;
  flex-shrink: 0;
  display: inline-block;
}

.dot-1 {
  background: var(--c1);
  box-shadow: 0 0 10px var(--c1), 0 0 22px var(--c1-glow);
}

.dot-2 {
  background: var(--c2);
  box-shadow: 0 0 10px var(--c2), 0 0 22px var(--c2-glow);
}

.system-tabs {
  display: flex;
  gap: 3px;
  background: rgba(0,0,0,0.25);
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  padding: 4px;
  margin-bottom: 20px;
  justify-content: center;
}

.tab {
  flex: 1;
  min-width: 0;
  padding: 7px 4px;
  border: none;
  border-radius: 7px;
  background: transparent;
  color: var(--text-sub);
  font-family: 'Outfit', sans-serif;
  font-size: 0.75rem;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.2s, color 0.2s, box-shadow 0.2s;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.tab:hover:not(.active) {
  color: var(--text);
  background: var(--surface-md);
}

.tab.active {
  font-weight: 700;
  background: var(--surface-hi);
  color: var(--text);
}

#foot-panel-1 .tab.active {
  color: var(--c1);
  box-shadow: 0 0 12px var(--c1-glow);
}

#foot-panel-2 .tab.active {
  color: var(--c2);
  box-shadow: 0 0 12px var(--c2-glow);
}

.input-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  margin-bottom: 22px;
}

.step-btn {
  width: 42px;
  height: 52px;
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  background: var(--surface-md);
  color: var(--text);
  font-size: 1.5rem;
  font-weight: 300;
  cursor: pointer;
  flex-shrink: 0;
  transition: all 0.15s;
  display: flex;
  align-items: center;
  justify-content: center;
  user-select: none;
}

.step-btn:hover {
  background: var(--surface-hi);
  border-color: var(--border-bright);
  transform: scale(1.06);
}

.step-btn:active {
  transform: scale(0.93);
}

.size-input {
  width: 130px;
  flex: none;
  background: rgba(0,0,0,0.3);
  border: 1.5px solid var(--border);
  border-radius: var(--r-sm);
  color: var(--text);
  font-family: 'Outfit', sans-serif;
  font-size: 2.4rem;
  font-weight: 800;
  text-align: center;
  padding: 8px 4px;
  transition: border-color 0.2s, box-shadow 0.2s;
  outline: none;
  appearance: textfield;
  -moz-appearance: textfield;
}

.size-input::-webkit-outer-spin-button,
.size-input::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }

#foot-panel-1 .size-input:focus {
  border-color: var(--c1);
  box-shadow: 0 0 0 3px var(--c1-glow);
}

#foot-panel-2 .size-input:focus {
  border-color: var(--c2);
  box-shadow: 0 0 0 3px var(--c2-glow);
}

.conversions-grid {
  display: flex;
  flex-direction: column;
  gap: 5px;
}

.conv-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 9px 13px;
  border-radius: 9px;
  background: rgba(0,0,0,0.15);
  border: 1px solid transparent;
  transition: background 0.2s, border-color 0.2s;
}

.conv-row.conv-current {
  background: var(--surface-md);
  border-color: var(--border);
}

#foot-panel-1 .conv-row.conv-current { border-color: rgba(34,211,238,0.25); }
#foot-panel-2 .conv-row.conv-current { border-color: rgba(251,146,60,0.25); }

.conv-label {
  color: var(--text-sub);
  font-size: 0.82rem;
  font-weight: 500;
}

.conv-value {
  font-size: 0.96rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.01em;
}

#foot-panel-1 .conv-row.conv-current .conv-value { color: var(--c1); }
#foot-panel-2 .conv-row.conv-current .conv-value { color: var(--c2); }

#vs-divider {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding-top: 72px;
  gap: 8px;
}

.vs-line {
  width: 1px;
  flex: 1;
  min-height: 24px;
  background: linear-gradient(to bottom, transparent, var(--border));
}

.vs-line:last-child {
  background: linear-gradient(to bottom, var(--border), transparent);
}

.vs-label {
  font-size: 0.7rem;
  font-weight: 800;
  color: var(--text-dim);
  letter-spacing: 0.2em;
  padding: 6px 0;
}

#comparison-section {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 28px;
  box-shadow: var(--shadow);
  backdrop-filter: blur(24px);
  -webkit-backdrop-filter: blur(24px);
}

.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 18px;
}

.section-header h2 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-sub);
  letter-spacing: 0.03em;
  text-transform: uppercase;
  font-size: 0.78rem;
}

#diff-display {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.diff-badge {
  padding: 5px 13px;
  border-radius: 20px;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  transition: all 0.3s;
}

.diff-badge.neutral {
  background: rgba(100,116,139,0.15);
  color: #94a3b8;
  border: 1px solid rgba(100,116,139,0.25);
}

.diff-badge.info {
  background: rgba(139,92,246,0.15);
  color: #c4b5fd;
  border: 1px solid rgba(139,92,246,0.3);
}

.diff-badge.highlight {
  background: rgba(34,211,238,0.12);
  color: var(--c1);
  border: 1px solid rgba(34,211,238,0.3);
}

#legend {
  display: flex;
  gap: 20px;
  margin-bottom: 20px;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-sub);
}

.legend-dot {
  width: 14px;
  height: 14px;
  border-radius: 3px;
}

#svg-container {
  overflow: auto;
  border-radius: 14px;
  background: rgba(0,0,0,0.25);
  border: 1px solid var(--border);
  display: flex;
  justify-content: center;
  align-items: flex-end;
  min-height: 300px;
  padding: 8px;
}

#foot-svg {
  display: block;
  max-width: 100%;
  transition: all 0.35s ease;
}

.width-toggle {
  margin-top: 18px;
  border-top: 1px solid var(--border);
  padding-top: 2px;
}

.width-toggle summary {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 4px;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-sub);
  cursor: pointer;
  list-style: none;
  transition: color 0.2s;
  user-select: none;
}

.width-toggle summary::-webkit-details-marker { display: none; }

.width-icon {
  font-size: 1rem;
  opacity: 0.6;
}

.width-arrow {
  margin-left: auto;
}

.width-arrow::after {
  content: '+';
  font-size: 1.1rem;
  font-weight: 300;
  color: var(--text-dim);
  transition: color 0.2s;
}

.width-toggle[open] .width-arrow::after {
  content: '−';
}

#foot-panel-1 .width-toggle[open] .width-arrow::after { color: var(--c1); }
#foot-panel-2 .width-toggle[open] .width-arrow::after { color: var(--c2); }

.width-toggle summary:hover { color: var(--text); }

.width-content {
  padding-bottom: 4px;
}

.width-tabs {
  margin-bottom: 14px !important;
}

.width-letter-display {
  width: 90px;
  text-align: center;
  font-size: 2rem;
  font-weight: 800;
  color: var(--text);
  user-select: none;
  letter-spacing: 0.02em;
}

#foot-panel-1 .width-letter-display { color: var(--c1); }
#foot-panel-2 .width-letter-display { color: var(--c2); }

.width-size-input {
  width: 100px !important;
  font-size: 1.6rem !important;
  padding: 6px 4px !important;
}

.width-conversions {
  margin-top: 4px;
}

.width-conv-row {
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 8px 13px;
  border-radius: 9px;
  background: rgba(0,0,0,0.15);
  font-size: 0.84rem;
}

.width-conv-row .conv-value {
  font-size: 0.84rem;
  font-weight: 600;
  color: var(--text-sub);
}

#size-chart-section,
#faq-section {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 28px;
  box-shadow: var(--shadow);
  backdrop-filter: blur(24px);
  -webkit-backdrop-filter: blur(24px);
}

#size-chart-section h2,
#faq-section h2 {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-sub);
  letter-spacing: 0.03em;
  text-transform: uppercase;
  margin-bottom: 8px;
}

.chart-intro {
  font-size: 0.85rem;
  color: var(--text-dim);
  margin-bottom: 18px;
  line-height: 1.5;
}

.table-scroll {
  overflow-x: auto;
  border-radius: 12px;
  border: 1px solid var(--border);
}

#size-chart {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
  font-variant-numeric: tabular-nums;
}

#size-chart thead {
  background: rgba(0,0,0,0.3);
}

#size-chart th {
  padding: 11px 16px;
  font-weight: 700;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-sub);
  text-align: center;
  border-bottom: 1px solid var(--border);
}

#size-chart td {
  padding: 10px 16px;
  text-align: center;
  color: var(--text);
  font-weight: 500;
  border-bottom: 1px solid rgba(255,255,255,0.03);
}

#size-chart tbody tr:nth-child(even) {
  background: rgba(255,255,255,0.02);
}

#size-chart tbody tr:hover {
  background: rgba(255,255,255,0.05);
}

#size-chart tbody tr td:first-child {
  color: var(--c1);
  font-weight: 700;
}

.faq-list {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-top: 12px;
}

.faq-item {
  background: rgba(0,0,0,0.2);
  border: 1px solid var(--border);
  border-radius: 12px;
  overflow: hidden;
  transition: border-color 0.25s;
}

.faq-item[open] {
  border-color: var(--border-bright);
}

.faq-item summary {
  padding: 14px 18px;
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--text);
  cursor: pointer;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  transition: color 0.2s;
}

.faq-item summary::-webkit-details-marker { display: none; }

.faq-item summary::after {
  content: '+';
  font-size: 1.2rem;
  font-weight: 300;
  color: var(--text-dim);
  flex-shrink: 0;
  transition: transform 0.25s, color 0.25s;
}

.faq-item[open] summary::after {
  content: '−';
  color: var(--c1);
}

.faq-item summary:hover {
  color: var(--c1);
}

.faq-item p {
  padding: 0 18px 16px;
  font-size: 0.86rem;
  color: var(--text-sub);
  line-height: 1.65;
}

.faq-item p strong {
  color: var(--text);
  font-weight: 600;
}

#main-footer {
  border-top: 1px solid var(--border);
  padding: 20px 32px;
  text-align: center;
  color: var(--text-dim);
  font-size: 0.76rem;
}

#main-footer strong {
  color: var(--text-sub);
}

.footer-seo {
  margin-top: 6px;
  font-size: 0.7rem;
  color: var(--text-dim);
  opacity: 0.7;
}

@media (max-width: 680px) {
  #panels-container {
    grid-template-columns: 1fr;
  }

  #vs-divider {
    flex-direction: row;
    padding-top: 0;
    gap: 12px;
  }

  .vs-line {
    flex: 1;
    min-height: 1px;
    width: auto;
    background: linear-gradient(to right, transparent, var(--border));
  }

  .vs-line:last-child {
    background: linear-gradient(to right, var(--border), transparent);
  }

  #main-header { padding: 16px 16px; }
  #main-content { padding: 20px 12px 32px; }
  #comparison-section { padding: 20px 14px; }
  #size-chart-section { padding: 20px 14px; }
  #faq-section { padding: 20px 14px; }

  #size-chart th,
  #size-chart td {
    padding: 8px 10px;
    font-size: 0.8rem;
  }
}