/* Colour carries meaning here, not decoration. Saturation tables are about
   two phases, so columns are coded by phase: liquid cool, vapour warm, the
   evaporation difference neutral. */

:root {
  --ink:        #101d2b;
  --ink-soft:   #4a5c6e;
  --ink-faint:  #8697a6;
  --paper:      #fcfcfa;
  --rule:       #dce1e7;
  --rule-hard:  #a9b6c2;

  --liquid:     #1f6fb2;
  --vapor:      #b4661a;
  --evap:       #6b7a88;

  --mark:       #fdf6c9;
  --mark-rule:  #d7a51a;

  --error:      #a4232b;
  --error-bg:   #fdf3f3;

  --mono: "IBM Plex Mono", ui-monospace, Menlo, monospace;
  --sans: "IBM Plex Sans", system-ui, "Segoe UI", sans-serif;
}

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

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.55;
}

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

.masthead {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  justify-content: space-between;
  gap: 1.5rem 2.5rem;
  padding: 1.75rem 1.5rem 1.25rem;
  border-bottom: 1px solid var(--rule-hard);
  max-width: 1180px;
  margin: 0 auto;
}

.masthead-title h1 {
  margin: 0;
  font-size: 1.375rem;
  font-weight: 600;
  letter-spacing: -0.015em;
}

.masthead-title p { margin: 0.1rem 0 0; color: var(--ink-faint); font-size: 0.875rem; }

.controls { display: flex; flex-wrap: wrap; align-items: flex-end; gap: 1rem; }
.field { display: flex; flex-direction: column; gap: 0.3rem; }
.field-label { font-size: 0.8125rem; color: var(--ink-soft); }

select, input[type="text"] {
  font-family: var(--sans);
  font-size: 0.9375rem;
  color: var(--ink);
  background: #fff;
  border: 1px solid var(--rule-hard);
  border-radius: 3px;
  padding: 0.45rem 0.6rem;
}

select { min-width: 17rem; }

.input-wrap { position: relative; display: inline-flex; }

.input-wrap input {
  font-family: var(--mono);
  font-size: 1rem;
  width: 9rem;
  padding-right: 3rem;
  font-variant-numeric: tabular-nums;
}

.input-unit {
  position: absolute;
  right: 0.6rem;
  top: 50%;
  transform: translateY(-50%);
  font-family: var(--mono);
  font-size: 0.875rem;
  color: var(--ink-faint);
  pointer-events: none;
}

main { max-width: 1180px; margin: 0 auto; padding: 1.5rem 1.5rem 5rem; }

.hint { margin: 0.5rem 0 0; color: var(--ink-faint); font-size: 0.9375rem; }

.error {
  margin: 1rem 0 0;
  padding: 0.75rem 0.9rem;
  border-left: 3px solid var(--error);
  background: var(--error-bg);
  color: var(--error);
  font-size: 0.9375rem;
}

.readout { margin-top: 1.5rem; }

.readout-head {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  padding-bottom: 0.6rem;
  border-bottom: 1px solid var(--rule);
}

.readout-head > span:first-child {
  font-family: var(--mono);
  font-size: 1.0625rem;
  font-weight: 500;
  font-variant-numeric: tabular-nums;
}

.readout-note { color: var(--ink-faint); font-size: 0.8125rem; }

.readout-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(9.5rem, 1fr));
  gap: 0.9rem 1.5rem;
  margin: 1rem 0 0;
}

.readout-grid > div { min-width: 0; }

.readout-grid dt {
  font-family: var(--mono);
  font-size: 0.8125rem;
  color: var(--ink-soft);
  margin-bottom: 0.15rem;
}

.readout-grid dd {
  margin: 0;
  font-family: var(--mono);
  font-size: 1.0625rem;
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.readout-grid dd .unit {
  font-size: 0.75rem;
  color: var(--ink-faint);
  margin-left: 0.2rem;
}

.phase-liquid { color: var(--liquid); }
.phase-vapor  { color: var(--vapor); }
.phase-evap   { color: var(--evap); }
.phase-index  { color: var(--ink); }

.table-wrap {
  margin-top: 2.25rem;
  overflow-x: auto;
  border-top: 1px solid var(--rule-hard);
  border-bottom: 1px solid var(--rule-hard);
}

table {
  border-collapse: collapse;
  font-family: var(--mono);
  font-size: 0.8125rem;
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
  min-width: 100%;
}

thead th {
  position: sticky;
  top: 0;
  background: var(--paper);
  text-align: right;
  font-weight: 500;
  padding: 0.6rem 0.7rem 0.5rem;
  border-bottom: 1px solid var(--rule-hard);
}

thead th .th-unit {
  display: block;
  font-size: 0.6875rem;
  color: var(--ink-faint);
  font-weight: 400;
}

tbody td {
  text-align: right;
  padding: 0.3rem 0.7rem;
  border-bottom: 1px solid var(--rule);
  color: var(--ink-soft);
}

tbody td:first-child { color: var(--ink); font-weight: 500; }

tr.source td { color: var(--ink); background: #f2f5f8; }
tr.source--upper td { border-bottom-color: var(--rule-hard); }
tr.source--lower td { border-top: 1px solid var(--rule-hard); }

tr.result td {
  background: var(--mark);
  color: var(--ink);
  font-weight: 500;
  border-bottom-color: var(--mark-rule);
}

tr.result td:first-child { box-shadow: inset 3px 0 0 var(--mark-rule); }

tr.result { animation: insert 240ms cubic-bezier(0.2, 0, 0.15, 1); }

@keyframes insert {
  from { opacity: 0; transform: translateY(-4px); }
  to   { opacity: 1; transform: none; }
}

@media (prefers-reduced-motion: reduce) { tr.result { animation: none; } }

.working { margin-top: 2.75rem; }
.working h2 { font-size: 0.9375rem; font-weight: 600; margin: 0 0 0.5rem; }

.working-intro {
  margin: 0 0 1rem;
  color: var(--ink-soft);
  font-size: 0.9375rem;
  max-width: 62ch;
}

.working-steps { display: grid; gap: 0.55rem; }

.step {
  font-family: var(--mono);
  font-size: 0.8125rem;
  font-variant-numeric: tabular-nums;
  color: var(--ink-soft);
  overflow-x: auto;
  padding-bottom: 0.15rem;
}

.step b { font-weight: 500; }
.step .out { color: var(--ink); font-weight: 600; }

sub {
  font-size: 0.72em;
  line-height: 0;
  vertical-align: baseline;
  position: relative;
  bottom: -0.22em;
}

@media (max-width: 640px) {
  .masthead { padding: 1.25rem 1rem 1rem; }
  main { padding: 1.25rem 1rem 4rem; }
  .controls { width: 100%; }
  select { min-width: 0; width: 100%; }
  .field-value, .input-wrap, .input-wrap input { width: 100%; }
}