:root {
  color-scheme: light;
  --paper: #f3f5f8;
  --surface: #ffffff;
  --ink: #141b26;
  --ink-soft: #4a5566;
  --rule: #d4dae3;
  --field-border: #7d8796;
  --accent: #2445c9;
  --accent-ink: #ffffff;
  --error: #b42318;
  --focus: #2445c9;
  /* Token colours: distinct hues that pass 4.5:1 on --paper as text. */
  --t0: #2445c9;
  --t1: #a3337a;
  --t2: #1d7a4a;
  --t3: #a14f0a;
  --t4: #6b3fc4;
  --t5: #0c6f86;
  --sans: system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --mono: ui-monospace, 'Cascadia Code', 'SF Mono', Menlo, Consolas, 'Liberation Mono', monospace;
  --measure: 72rem;
  --gutter: clamp(1rem, 4vw, 3rem);
}

@media (prefers-color-scheme: dark) {
  :root {
    color-scheme: dark;
    --paper: #10151d;
    --surface: #171e29;
    --ink: #e8edf4;
    --ink-soft: #a5b0c0;
    --rule: #2c3646;
    --field-border: #6b778a;
    --accent: #8ea6ff;
    --accent-ink: #0b1020;
    --error: #ff8f84;
    --focus: #8ea6ff;
    --t0: #8ea6ff;
    --t1: #f08cc8;
    --t2: #6fd39c;
    --t3: #f2aa63;
    --t4: #b9a1ff;
    --t5: #63cfe6;
  }
}

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

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

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font: 1rem/1.55 var(--sans);
}

code,
.mono {
  font-family: var(--mono);
  font-size: 0.92em;
}

a {
  color: var(--accent);
  text-underline-offset: 0.2em;
}

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

.skip {
  position: absolute;
  left: 1rem;
  top: -4rem;
  padding: 0.5rem 0.75rem;
  background: var(--accent);
  color: var(--accent-ink);
  z-index: 1;
}

.skip:focus {
  top: 1rem;
}

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

.masthead,
main,
.footer {
  max-width: var(--measure);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

/* Masthead */

.masthead {
  padding-block: clamp(2.5rem, 7vw, 5rem) 2rem;
}

.brand {
  margin: 0 0 1rem;
  font-family: var(--mono);
  font-size: 0.95rem;
  color: var(--ink-soft);
}

h1 {
  max-width: 22ch;
  margin: 0;
  font-size: clamp(2rem, 5.2vw, 3.6rem);
  line-height: 1.08;
  letter-spacing: -0.02em;
  font-weight: 700;
  text-wrap: balance;
}

.lede {
  max-width: 60ch;
  margin: 1.25rem 0 0;
  color: var(--ink-soft);
  font-size: 1.08rem;
}

.masthead nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1.5rem;
  margin-top: 1.5rem;
}

.masthead nav a {
  display: inline-block;
  padding-block: 0.6rem;
}

/* Sections */

main > section {
  padding-block: 2.5rem;
  border-top: 1px solid var(--rule);
}

h2 {
  margin: 0 0 1.25rem;
  font-size: 1.5rem;
  line-height: 1.2;
  letter-spacing: -0.01em;
}

h3 {
  margin: 0 0 0.5rem;
  font-size: 1.05rem;
}

.section-intro {
  max-width: 64ch;
  margin: -0.5rem 0 1.5rem;
  color: var(--ink-soft);
}

/* Form controls */

.field {
  display: grid;
  gap: 0.35rem;
  align-content: start;
}

label,
legend {
  font-weight: 600;
  font-size: 0.95rem;
}

input,
select {
  width: 100%;
  min-height: 2.75rem;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--field-border);
  border-radius: 6px;
  background: var(--surface);
  color: var(--ink);
  font: inherit;
}

#pattern,
#read-input {
  font-family: var(--mono);
}

input::placeholder {
  color: var(--ink-soft);
  opacity: 1;
}

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

.hint {
  margin: 0;
  max-width: 64ch;
  color: var(--ink-soft);
  font-size: 0.9rem;
}

.error {
  margin: 0;
  color: var(--error);
  font-size: 0.9rem;
}

.error:empty {
  display: none;
}

button {
  min-height: 2.75rem;
  padding: 0.5rem 1.1rem;
  border: 1px solid var(--field-border);
  border-radius: 6px;
  background: var(--surface);
  color: var(--ink);
  font: inherit;
  font-weight: 600;
  cursor: pointer;
  transition:
    background-color 120ms ease,
    border-color 120ms ease;
}

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

button.primary {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-ink);
}

button.primary:hover {
  filter: brightness(1.08);
}

button.quiet {
  border-color: transparent;
  background: transparent;
  color: var(--ink-soft);
}

button.quiet:hover {
  color: var(--ink);
}

button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* Pattern */

.pattern-setup {
  display: grid;
  grid-template-columns: minmax(12rem, 16rem) 1fr;
  gap: 1rem 1.5rem;
}

.values {
  margin: 1.75rem 0 0;
  padding: 0;
  border: 0;
}

.values legend {
  margin-bottom: 0.75rem;
  padding: 0;
}

.values[hidden] {
  display: none;
}

.value-fields {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(13rem, 1fr));
  gap: 1rem 1.5rem;
}

.value-fields .optional {
  font-weight: 400;
  color: var(--ink-soft);
}

/* The specimen: the ID, set large, with every token labelled underneath. */

.specimen {
  margin-top: 2.5rem;
}

.specimen-label {
  margin: 0 0 0.5rem;
  color: var(--ink-soft);
  font-size: 0.95rem;
}

.id-display {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  min-height: 6.5rem;
  margin: 0;
  font-family: var(--mono);
  font-size: clamp(1.6rem, 5.5vw, 4rem);
  line-height: 1.15;
  letter-spacing: -0.01em;
  overflow-wrap: anywhere;
}

.id-display .lit,
.id-display .tok {
  display: inline-flex;
  flex-direction: column;
  min-width: 0;
}

.id-display .lit {
  color: var(--ink-soft);
  white-space: pre;
}

.id-display .val {
  padding-bottom: 0.15em;
  border-bottom: 3px solid var(--tone);
  overflow-wrap: anywhere;
}

.id-display .tag {
  /* As wide as the value, never wider: a long label must not open gaps that are not in the ID. */
  width: 0;
  min-width: 100%;
  overflow: hidden;
  text-overflow: ellipsis;
  margin-top: 0.4rem;
  padding-right: 0.25rem;
  color: var(--tone);
  font-size: 0.8rem;
  line-height: 1.3;
  letter-spacing: 0;
  white-space: nowrap;
}

.id-display:has(.placeholder) {
  min-height: 0;
}

.id-display .placeholder {
  color: var(--ink-soft);
  font-family: var(--sans);
  font-size: 1.1rem;
  line-height: 1.5;
  letter-spacing: 0;
}

.id-display .plain {
  overflow-wrap: anywhere;
}

.tone-0 {
  --tone: var(--t0);
}
.tone-1 {
  --tone: var(--t1);
}
.tone-2 {
  --tone: var(--t2);
}
.tone-3 {
  --tone: var(--t3);
}
.tone-4 {
  --tone: var(--t4);
}
.tone-5 {
  --tone: var(--t5);
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 1.5rem;
}

.history {
  margin-top: 2.5rem;
}

.history-list {
  margin: 0;
  padding-left: 1.25rem;
  font-family: var(--mono);
  font-size: 1rem;
}

.history-list li {
  padding-block: 0.2rem;
  overflow-wrap: anywhere;
}

.history-list li::marker {
  color: var(--ink-soft);
}

/* Formats table */

.table-wrap {
  overflow-x: auto;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
}

th,
td {
  padding: 0.7rem 0.75rem 0.7rem 0;
  border-bottom: 1px solid var(--rule);
  text-align: left;
  vertical-align: middle;
}

th {
  color: var(--ink-soft);
  font-weight: 600;
}

td.example {
  font-family: var(--mono);
  overflow-wrap: anywhere;
}

td.row-actions {
  white-space: nowrap;
  text-align: right;
  padding-right: 0;
}

td.row-actions button + button {
  margin-left: 0.5rem;
}

/* Phones: the table turns into a list of labelled rows. */
@media (width < 44rem) {
  .pattern-setup {
    grid-template-columns: 1fr;
  }

  .id-display {
    min-height: 4.5rem;
  }

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

  tr {
    display: block;
    padding-block: 0.75rem;
    border-bottom: 1px solid var(--rule);
  }

  th,
  td {
    padding: 0.2rem 0;
    border: 0;
  }

  th {
    display: block;
    color: var(--ink);
    font-size: 1.05rem;
  }

  td {
    display: grid;
    grid-template-columns: 7.5rem minmax(0, 1fr);
    gap: 0.75rem;
  }

  td::before {
    content: attr(data-label);
    color: var(--ink-soft);
    font-family: var(--sans);
    font-weight: 600;
  }

  td.row-actions {
    display: flex;
    justify-content: flex-start;
    padding-top: 0.5rem;
  }

  td.row-actions::before {
    content: none;
  }
}

/* Read */

.read-result {
  display: grid;
  grid-template-columns: max-content 1fr;
  gap: 0.4rem 1.5rem;
  margin: 1.5rem 0 0;
}

.read-result dt {
  color: var(--ink-soft);
  font-weight: 600;
}

.read-result dd {
  margin: 0;
  font-family: var(--mono);
  overflow-wrap: anywhere;
}

.read-note {
  margin: 1.5rem 0 0;
  color: var(--ink-soft);
}

/* Footer */

.footer {
  padding-block: 2rem 3rem;
  /* A rule as wide as the content, like the section borders inside main. */
  background: linear-gradient(var(--rule), var(--rule)) center top / calc(100% - 2 * var(--gutter)) 1px no-repeat;
  color: var(--ink-soft);
  font-size: 0.95rem;
}

@media (prefers-reduced-motion: reduce) {
  * {
    transition: none !important;
  }
}