:root {
  color-scheme: light dark;
  --fg: #1b1f24;
  --muted: #57606a;
  --bg: #f6f8fa;
  --card: #ffffff;
  --line: #d0d7de;
  --accent: #0b5cad;
  --accent-fg: #ffffff;
  --error: #b3261e;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  line-height: 1.5;
}

@media (prefers-color-scheme: dark) {
  :root {
    --fg: #e6edf3;
    --muted: #9da7b1;
    --bg: #0d1117;
    --card: #161b22;
    --line: #30363d;
    --accent: #4c9be8;
    --accent-fg: #0d1117;
    --error: #ff8a80;
  }
}

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

[hidden] {
  display: none !important;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
}

.page-header,
main,
.page-footer {
  width: 100%;
  max-width: 44rem;
  margin: 0 auto;
  padding: 0 1rem;
}

.page-header {
  padding-top: 1.5rem;
}

h1 {
  font-size: 1.6rem;
  margin: 0 0 0.25rem;
}

h2 {
  font-size: 1.1rem;
  margin: 0 0 0.75rem;
}

.page-header p,
.page-footer p,
.hint,
caption {
  color: var(--muted);
  font-size: 0.9rem;
}

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  padding: 1rem;
  margin: 1rem 0;
}

.field {
  margin-bottom: 1rem;
}

.field-label {
  display: block;
  font-weight: 600;
  margin-bottom: 0.35rem;
}

.hint,
.error {
  margin: 0.35rem 0 0;
}

.error {
  color: var(--error);
  font-weight: 600;
}

input[type="text"] {
  width: 100%;
  font: inherit;
  font-size: 1.1rem;
  padding: 0.5rem 0.65rem;
  border: 1px solid var(--line);
  border-radius: 0.375rem;
  background: var(--card);
  color: var(--fg);
}

input[aria-invalid="true"] {
  border-color: var(--error);
}

.buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

button {
  font: inherit;
  min-height: 2.5rem;
  min-width: 2.75rem;
  padding: 0.35rem 0.8rem;
  border: 1px solid var(--line);
  border-radius: 0.375rem;
  background: var(--card);
  color: var(--fg);
  cursor: pointer;
}

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

button[aria-pressed="true"],
button.primary {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-fg);
}

button:focus-visible,
input:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 2px;
}

.swap-row {
  margin-bottom: 1rem;
}

.actions {
  border-top: 1px solid var(--line);
  padding-top: 1rem;
}

output {
  display: block;
  font-size: 1.6rem;
  font-weight: 700;
  overflow-wrap: anywhere;
}

.note {
  margin: 0.25rem 0 0;
  color: var(--muted);
  font-style: italic;
}

.formula {
  margin: 0.75rem 0 0;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9rem;
  overflow-wrap: anywhere;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}

caption {
  text-align: left;
  padding-bottom: 0.5rem;
}

/* Wrap only between words: `anywhere` let auto table layout split unit names letter by letter. */
th,
td {
  text-align: left;
  padding: 0.35rem 0.4rem;
  border-bottom: 1px solid var(--line);
  overflow-wrap: break-word;
  hyphens: manual;
}

/* Narrow screens: each factor row becomes a card of labelled Unit / Symbol / Factor lines. */
@media (max-width: 36rem) {
  #factors,
  #factors caption,
  #factors tbody,
  #factors tr {
    display: block;
    width: 100%;
  }

  #factors thead {
    position: absolute;
    width: 1px;
    height: 1px;
    overflow: hidden;
    clip-path: inset(50%);
    white-space: nowrap;
  }

  #factors tr {
    border: 1px solid var(--line);
    border-radius: 0.375rem;
    padding: 0.2rem 0.65rem;
    margin-bottom: 0.5rem;
  }

  #factors td {
    display: grid;
    grid-template-columns: 4.25rem minmax(0, 1fr);
    gap: 0.5rem;
    padding: 0.3rem 0;
  }

  #factors td:last-child {
    border-bottom: 0;
  }

  #factors td::before {
    content: attr(data-label);
    font-weight: 600;
    color: var(--muted);
  }
}

.page-footer {
  padding-bottom: 2rem;
}