/* MathTools — precision instrument UI (DataTools-aligned tokens) */

:root,
[data-theme="dark"] {
  --bg: #0f1419;
  --bg-accent: #1a2332;
  --surface: #171c24;
  --surface-2: #1f2630;
  --border: #2d3644;
  --text: #eef2f8;
  --muted: #93a0b4;
  --accent: #3b82f6;
  --accent-hover: #2563eb;
  --accent-soft: color-mix(in srgb, var(--accent) 16%, transparent);
  --accent-ink: #93c5fd;
  --warning-bg: rgba(251, 191, 36, 0.12);
  --warning-text: #fcd34d;
  --danger: #f87171;
  --danger-soft: rgba(248, 113, 113, 0.14);
  --radius: 10px;
  --shadow: 0 8px 24px rgba(0, 0, 0, 0.28);
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --font-body: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --font-display: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --font-mono: ui-monospace, "SF Mono", "Cascadia Code", "Consolas", monospace;
  /* Aliases for calculator / toolbox pages */
  --ink: var(--text);
  --ink-muted: var(--muted);
  --line: var(--border);
  --line-strong: #3d4a5c;
  --bg-elevated: var(--surface-2);
}

[data-theme="light"] {
  --bg: #eef2f7;
  --bg-accent: #dbeafe;
  --surface: #ffffff;
  --surface-2: #f8fafc;
  --border: #d5dde8;
  --text: #111827;
  --muted: #64748b;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --accent-soft: color-mix(in srgb, var(--accent) 12%, transparent);
  --accent-ink: #1d4ed8;
  --warning-bg: #fef3c7;
  --warning-text: #92400e;
  --danger: #dc2626;
  --danger-soft: #fee2e2;
  --shadow: 0 8px 24px rgba(15, 23, 42, 0.08);
  --line-strong: #b6c2d2;
}

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

html {
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  min-height: 100dvh;
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.5;
  color: var(--text);
  background: radial-gradient(circle at top, var(--bg-accent) 0%, var(--bg) 55%);
  -webkit-font-smoothing: antialiased;
}

.page-bg {
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background:
    linear-gradient(rgba(45, 54, 68, 0.18) 1px, transparent 1px),
    linear-gradient(90deg, rgba(45, 54, 68, 0.18) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse 75% 60% at 50% 0%, #000 20%, transparent 75%);
  opacity: 0.45;
}

[data-theme="light"] .page-bg {
  background:
    linear-gradient(rgba(37, 99, 235, 0.08) 1px, transparent 1px),
    linear-gradient(90deg, rgba(37, 99, 235, 0.08) 1px, transparent 1px);
  background-size: 48px 48px;
  opacity: 0.55;
}

.shell {
  width: min(920px, calc(100% - 2rem));
  margin: 0 auto;
  padding: clamp(1.5rem, 4vw, 2.75rem) 0 clamp(2.5rem, 6vw, 4rem);
}

.site-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 1.25rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

.brand-mark {
  flex-shrink: 0;
  color: var(--accent);
}

.brand-name {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(1.75rem, 4vw, 2.1rem);
  letter-spacing: -0.03em;
  line-height: 1.1;
  color: var(--text);
}

.brand-tagline {
  margin: 0.25rem 0 0;
  font-size: 0.95rem;
  color: var(--muted);
  font-weight: 500;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  flex-shrink: 0;
}

.theme-toggle {
  appearance: none;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 0.875rem;
  font-weight: 600;
  padding: 0.5rem 0.85rem;
  border-radius: 8px;
  cursor: pointer;
  transition: border-color 0.18s var(--ease), color 0.18s var(--ease), background 0.18s var(--ease);
}

.theme-toggle:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.theme-toggle:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.app-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin: 0 0 1.1rem;
}

.app-nav-link {
  appearance: none;
  display: inline-flex;
  align-items: center;
  min-height: 2.5rem;
  padding: 0.45rem 0.85rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 0.875rem;
  font-weight: 600;
  text-decoration: none;
  transition: color 0.18s var(--ease), border-color 0.18s var(--ease), background 0.18s var(--ease);
}

.app-nav-link:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.app-nav-link:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.app-nav-link.is-active {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent);
}

.page-help {
  margin: 0 0 1rem;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--surface);
}

.page-help > summary {
  cursor: pointer;
  list-style: none;
  padding: 0.65rem 0.9rem;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--accent);
}

.page-help > summary::-webkit-details-marker {
  display: none;
}

.page-help-body {
  padding: 0 0.95rem 0.95rem;
  border-top: 1px solid var(--border);
}

.page-help-body p {
  margin: 0.65rem 0 0;
  font-size: 0.9rem;
  line-height: 1.45;
  color: var(--text);
}

.page-help-body ul {
  margin: 0.5rem 0 0;
  padding-left: 1.15rem;
  font-size: 0.86rem;
  line-height: 1.45;
  color: var(--muted);
}

.page-help-body li + li {
  margin-top: 0.3rem;
}

.category-rail {
  display: flex;
  gap: 0.4rem;
  overflow-x: auto;
  scrollbar-width: thin;
  scrollbar-color: var(--line-strong) transparent;
  padding: 0.15rem 0 0.85rem;
  margin-bottom: 0.35rem;
  -webkit-overflow-scrolling: touch;
}

.category-rail::-webkit-scrollbar {
  height: 4px;
}

.category-rail::-webkit-scrollbar-thumb {
  background: var(--line-strong);
  border-radius: 2px;
}

.category-chip {
  flex: 0 0 auto;
  appearance: none;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--muted);
  font-family: var(--font-body);
  font-size: 0.875rem;
  font-weight: 600;
  padding: 0.45rem 0.85rem;
  border-radius: 8px;
  cursor: pointer;
  transition:
    color 0.2s var(--ease),
    border-color 0.2s var(--ease),
    background 0.2s var(--ease),
    box-shadow 0.2s var(--ease);
}

.category-chip:hover {
  color: var(--text);
  border-color: var(--line-strong);
}

.category-chip:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.category-chip.is-active {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-soft);
}

.converter-stage {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: clamp(1.15rem, 3vw, 1.65rem);
}

.convert-row {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: clamp(0.75rem, 2vw, 1.25rem);
  align-items: stretch;
}

.panel {
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
  min-width: 0;
}

.panel-label,
.panel-label-row .panel-label {
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
}

.panel-label-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  min-height: 1.1rem;
}

.value-field {
  width: 100%;
  margin: 0;
  padding: 0.75rem 0.9rem;
  font-family: var(--font-mono);
  font-size: clamp(1.45rem, 4vw, 2rem);
  font-weight: 500;
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.02em;
  color: var(--text);
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 8px;
  line-height: 1.25;
  transition: border-color 0.18s var(--ease), box-shadow 0.18s var(--ease);
}

input.value-field {
  appearance: none;
}

.value-field:focus,
.value-field:focus-visible {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 28%, transparent);
}

.value-result {
  min-height: 3.4rem;
  display: flex;
  align-items: center;
  word-break: break-all;
  cursor: text;
}

.value-result.is-editing {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 28%, transparent);
}

.value-result.is-error {
  color: var(--danger);
  background: var(--danger-soft);
}

.value-result.is-ticking {
  animation: tick-read 0.45s var(--ease);
}

@keyframes tick-read {
  0% {
    opacity: 0.3;
    transform: translateY(5px);
    color: var(--accent-ink);
  }
  55% {
    opacity: 1;
    transform: translateY(0);
  }
  100% {
    color: var(--text);
  }
}

.unit-select {
  appearance: none;
  width: 100%;
  padding: 0.55rem 2.1rem 0.55rem 0.75rem;
  font-family: var(--font-body);
  font-size: 0.92rem;
  font-weight: 500;
  color: var(--text);
  background-color: var(--surface-2);
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1.2 1.2 6 6l4.8-4.8' stroke='%2393a0b4' stroke-width='1.4' fill='none' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.75rem center;
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  transition: border-color 0.18s var(--ease);
}

[data-theme="light"] .unit-select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1.2 1.2 6 6l4.8-4.8' stroke='%2364748b' stroke-width='1.4' fill='none' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
}

.unit-select:hover {
  border-color: var(--line-strong);
}

.unit-select:focus-visible {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 28%, transparent);
}

.swap-btn {
  align-self: center;
  display: grid;
  place-items: center;
  width: 2.75rem;
  height: 2.75rem;
  margin-top: 1.15rem;
  border: 1px solid var(--border);
  border-radius: 50%;
  background: var(--surface-2);
  color: var(--accent);
  cursor: pointer;
  transition: background 0.2s var(--ease), border-color 0.2s var(--ease), transform 0.2s var(--ease);
}

.swap-btn:hover {
  background: var(--accent-soft);
  border-color: var(--accent);
}

.swap-btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}

.swap-btn:active {
  transform: scale(0.94);
}

.swap-btn.is-rotating svg {
  animation: swap-spin 0.42s var(--ease);
}

@keyframes swap-spin {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(180deg);
  }
}

.copy-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  appearance: none;
  border: none;
  background: transparent;
  color: var(--muted);
  font-family: var(--font-body);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  padding: 0.15rem 0.25rem;
  cursor: pointer;
  border-radius: 4px;
  transition: color 0.15s var(--ease);
}

.copy-btn:hover:not(:disabled) {
  color: var(--accent);
}

.copy-btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.copy-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.copy-btn.is-copied {
  color: var(--accent);
}

.formula-note {
  margin: 1rem 0 0;
  font-size: 0.875rem;
  color: var(--muted);
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  line-height: 1.45;
}

.input-error {
  margin: 0.75rem 0 0;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--danger);
}

.popular-section {
  margin-top: 1.75rem;
}

.popular-heading {
  margin: 0 0 0.75rem;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
}

.popular-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.popular-chip {
  appearance: none;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 0.875rem;
  font-weight: 600;
  padding: 0.5rem 0.85rem;
  border-radius: 8px;
  cursor: pointer;
  transition: border-color 0.18s var(--ease), color 0.18s var(--ease), background 0.18s var(--ease);
}

.popular-chip:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-soft);
}

.popular-chip:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.site-footer {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem 1.25rem;
  margin-top: 2.5rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--border);
  font-size: 0.875rem;
  color: var(--muted);
}

.site-footer p {
  margin: 0;
}

.footer-link {
  color: var(--accent);
  font-weight: 600;
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.15s var(--ease);
}

.footer-link:hover {
  border-bottom-color: var(--accent);
}

.footer-link:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}

.toast {
  position: fixed;
  left: 50%;
  bottom: 1.5rem;
  transform: translateX(-50%) translateY(8px);
  padding: 0.65rem 1.1rem;
  background: var(--text);
  color: var(--bg);
  font-size: 0.875rem;
  font-weight: 500;
  border-radius: 8px;
  box-shadow: var(--shadow);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s var(--ease), transform 0.2s var(--ease);
  z-index: 50;
}

.toast.is-visible {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

/* Legacy hint badge used by calculator / toolbox headers */
.category-hint {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-ink);
  background: var(--accent-soft);
  padding: 0.35rem 0.65rem;
  border-radius: 4px;
}

html.js .reveal {
  opacity: 0;
  transform: translateY(10px);
  transition: opacity 0.55s var(--ease), transform 0.55s var(--ease);
  transition-delay: var(--reveal-delay, 0ms);
}

html.js body.is-ready .reveal,
html:not(.js) .reveal {
  opacity: 1;
  transform: translateY(0);
}

@media (prefers-reduced-motion: reduce) {
  .reveal,
  .value-result.is-ticking,
  .swap-btn.is-rotating svg {
    animation: none !important;
    transition: none !important;
    opacity: 1 !important;
    transform: none !important;
  }
}

@media (max-width: 640px) {
  .shell {
    width: min(100% - 1.25rem, 920px);
  }

  .site-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.75rem;
  }

  .convert-row {
    grid-template-columns: 1fr;
    gap: 0.65rem;
  }

  .swap-btn {
    margin: 0 auto;
    width: 2.5rem;
    height: 2.5rem;
  }
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}