:root {
  --bg: #ffffff;
  --fg: #111418;
  --muted: #55606d;
  --accent: #2563eb;
  --accent-soft: #dbeafe;
  --border: #e5e7eb;
  --card: #f7f9fc;
  --focus: #2563eb;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b0d12;
    --fg: #e8ebf0;
    --muted: #9aa3b2;
    --accent: #60a5fa;
    --accent-soft: #1a2f52;
    --border: #242833;
    --card: #151923;
    --focus: #60a5fa;
  }
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--fg);
  font: 16px/1.55 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -webkit-text-size-adjust: 100%;
}

main {
  max-width: 720px;
  margin: 0 auto;
  padding: 1rem clamp(1rem, 4vw, 1.5rem) 3rem;
}

header h1 {
  font-size: clamp(1.5rem, 5vw, 2rem);
  line-height: 1.2;
  margin: 0.5rem 0 0.25rem;
  letter-spacing: -0.01em;
}

header .sub {
  color: var(--muted);
  margin: 0 0 1.25rem;
  font-size: 0.95rem;
}

h2 {
  font-size: 1.2rem;
  margin: 2.25rem 0 0.75rem;
  letter-spacing: -0.005em;
}

p { margin: 0.5rem 0; }

a { color: var(--accent); }

/* Converter card */
.converter {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1rem;
}

.pace-fields {
  display: grid;
  gap: 0.75rem;
  grid-template-columns: 1fr;
}

@media (min-width: 520px) {
  .pace-fields { grid-template-columns: 1fr 1fr; }
}

.pace-field label {
  display: block;
  font-size: 0.8125rem;
  color: var(--muted);
  margin-bottom: 0.25rem;
  letter-spacing: 0.02em;
}

.pace-field input[type="text"] {
  width: 100%;
  min-height: 48px;
  padding: 0.5rem 0.75rem;
  font-size: 1.375rem;
  font-variant-numeric: tabular-nums;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg);
  color: var(--fg);
  -webkit-appearance: none;
  appearance: none;
}

.pace-field input[type="text"]:focus {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
  border-color: var(--focus);
}

.pace-field input[type="text"].invalid {
  border-color: #dc2626;
  box-shadow: 0 0 0 1px #dc2626;
}

.pace-field input[type="text"].invalid:focus {
  outline-color: #dc2626;
  border-color: #dc2626;
}

@media (prefers-color-scheme: dark) {
  .pace-field input[type="text"].invalid {
    border-color: #f87171;
    box-shadow: 0 0 0 1px #f87171;
  }
  .pace-field input[type="text"].invalid:focus {
    outline-color: #f87171;
    border-color: #f87171;
  }
}

/* Slider */
.slider-wrap { margin-top: 1.25rem; }

.slider-label {
  display: block;
  font-size: 0.8125rem;
  color: var(--muted);
  margin-bottom: 0.5rem;
}

.slider-wrap input[type="range"] {
  width: 100%;
  min-height: 44px;
  accent-color: var(--accent);
}

/* Keyboard focus ring on the slider — UA default drops out in WebKit
   and is inconsistent cross-browser, so pin our own :focus-visible. */
.slider-wrap input[type="range"]:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 4px;
  border-radius: 4px;
}

.slider-wrap input[type="range"]:focus:not(:focus-visible) {
  outline: none;
}

.slider-labels {
  display: flex;
  justify-content: space-between;
  font-size: 0.75rem;
  color: var(--muted);
  margin-top: 0.25rem;
}

/* Race projections */
.projections {
  display: grid;
  gap: 0.5rem;
  grid-template-columns: repeat(2, 1fr);
  margin-top: 1.25rem;
}

@media (min-width: 520px) {
  .projections { grid-template-columns: repeat(4, 1fr); }
}

.projection {
  background: var(--bg);
  color: inherit;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.625rem 0.5rem;
  min-height: 44px;
  width: 100%;
  text-align: center;
  font: inherit;
  cursor: pointer;
  -webkit-appearance: none;
  appearance: none;
  touch-action: manipulation;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

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

.projection:active { background: var(--card); }

.projection:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
  border-color: var(--focus);
}

.projection:focus:not(:focus-visible) { outline: none; }

.projection-label {
  display: block;
  font-size: 0.6875rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-weight: 600;
}

.projection-value {
  display: block;
  font-variant-numeric: tabular-nums;
  font-weight: 600;
  font-size: 1.125rem;
  margin-top: 0.125rem;
}

/* Share button */
.share-row {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  flex-wrap: wrap;
  margin-top: 1.25rem;
}

.share-btn {
  min-height: 44px;
  padding: 0.5rem 1rem;
  font: inherit;
  font-size: 0.9375rem;
  font-weight: 600;
  color: #ffffff;
  background: var(--accent);
  border: 1px solid var(--accent);
  border-radius: 10px;
  cursor: pointer;
  -webkit-appearance: none;
  appearance: none;
}

.share-btn:hover { filter: brightness(0.95); }

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

@media (prefers-color-scheme: dark) {
  /* Light accent needs dark text for AA contrast. */
  .share-btn { color: var(--bg); }
}

.share-feedback {
  color: var(--muted);
  font-size: 0.875rem;
  opacity: 0;
  transition: opacity 0.3s ease;
}

.share-feedback.visible { opacity: 1; }

.share-manual {
  flex: 1 1 100%;
  min-height: 44px;
  padding: 0.5rem 0.75rem;
  font-size: 0.9375rem;
  font-variant-numeric: tabular-nums;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg);
  color: var(--fg);
  -webkit-appearance: none;
  appearance: none;
}

/* Tables */
.quick-ref p { color: var(--muted); }

table {
  width: 100%;
  border-collapse: collapse;
  font-variant-numeric: tabular-nums;
  margin-top: 0.75rem;
}

th, td {
  padding: 0.5rem 0.25rem;
  text-align: left;
  border-bottom: 1px solid var(--border);
  font-size: 0.9375rem;
}

th {
  font-weight: 600;
  color: var(--muted);
  font-size: 0.8125rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* How-to + common paces */
ol, ul { padding-left: 1.25rem; }
ol li, ul li { margin-bottom: 0.5rem; }

.formula {
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  background: var(--accent-soft);
  color: var(--fg);
  padding: 0.125rem 0.375rem;
  border-radius: 4px;
  font-size: 0.9em;
}

.formula-line { color: var(--muted); }

/* Goal-time → required pace reverse calculator */
.goal-pace p { color: var(--muted); }

.goal-rows {
  display: grid;
  gap: 0.625rem;
  margin-top: 0.75rem;
}

.goal-row {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.375rem;
  align-items: center;
  padding: 0.625rem 0.75rem;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 10px;
}

@media (min-width: 481px) {
  .goal-row {
    grid-template-columns: 5.5rem 1fr auto;
    gap: 0.75rem;
  }
}

.goal-row label {
  font-weight: 600;
  font-size: 0.9375rem;
  letter-spacing: 0.01em;
}

.goal-row input[type="text"] {
  width: 100%;
  min-height: 44px;
  padding: 0.5rem 0.75rem;
  font-size: 1.0625rem;
  font-variant-numeric: tabular-nums;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--fg);
  -webkit-appearance: none;
  appearance: none;
}

.goal-row input[type="text"]:focus {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
  border-color: var(--focus);
}

.goal-row input[type="text"].invalid {
  border-color: #dc2626;
  box-shadow: 0 0 0 1px #dc2626;
}

@media (prefers-color-scheme: dark) {
  .goal-row input[type="text"].invalid {
    border-color: #f87171;
    box-shadow: 0 0 0 1px #f87171;
  }
}

/* Rendered as a <button> so the required pace is tappable — click copies
   "{label} goal {entered} → {km} (/mi {mi})" to the clipboard. Hover/focus
   treatment mirrors .projection tiles. */
.goal-out {
  font-variant-numeric: tabular-nums;
  font-weight: 600;
  font-size: 0.9375rem;
  color: var(--fg);
  white-space: nowrap;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.5rem 0.75rem;
  min-height: 44px;
  font-family: inherit;
  cursor: pointer;
  -webkit-appearance: none;
  appearance: none;
  touch-action: manipulation;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.goal-out:hover { border-color: var(--accent); }

.goal-out:active { background: var(--card); }

.goal-out:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
  border-color: var(--focus);
}

.goal-out:focus:not(:focus-visible) { outline: none; }

/* FAQ */
dl dt {
  font-weight: 600;
  margin-top: 1rem;
}

dl dd {
  margin: 0.25rem 0 0;
  color: var(--muted);
}

/* Footer */
footer {
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.8125rem;
  text-align: center;
}