:root {
  --bg: #383838;
  --bar: #3d3d3d;
  --row: #4b4b4b;
  --row-alt: #505050;
  --card: #4f4f4f;
  --divider: #5e5e5e;
  --text: #ffffff;
  --muted: #b9b9b9;
  --line: #9a9a9a;
  --accent: #f26b2a;
  --field: #f5f5f5;
  --field-text: #1d1d1d;
  --placeholder: #b4b4b4;
  --error: #ff8a80;
  --gutter: 16px;
  color-scheme: dark;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #f2f2f6;
    --bar: #f8f8fa;
    --row: #e9e9ee;
    --row-alt: #e2e2e8;
    --card: #ffffff;
    --divider: #d4d4da;
    --text: #1d1d1f;
    --muted: #6b6b72;
    --line: #8d8d94;
    --field: #ffffff;
    --error: #c62828;
    color-scheme: light;
  }
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 17px/1.35 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  -webkit-text-size-adjust: 100%;
  -webkit-tap-highlight-color: transparent;
}

#app {
  max-width: 720px;
  margin: 0 auto;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
}

/* ---------- top bar ---------- */

.bar {
  position: sticky;
  top: 0;
  z-index: 5;
  display: grid;
  grid-template-columns: 52px 1fr auto;
  align-items: center;
  gap: 12px;
  padding: calc(env(safe-area-inset-top) + 10px) var(--gutter) 10px;
  background: var(--bg);
}
.bar h1 {
  margin: 0;
  font-size: 20px;
  font-weight: 650;
  text-align: center;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.round, .pill button {
  border: 0;
  color: var(--text);
  background: transparent;
  cursor: pointer;
  display: grid;
  place-items: center;
}
.round {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--row);
}
.round svg, .pill svg { width: 24px; height: 24px; }
.round-spacer { width: 52px; }
.pill {
  display: flex;
  gap: 4px;
  padding: 0 6px;
  height: 48px;
  border-radius: 24px;
  background: var(--row);
}
.pill button { width: 44px; height: 48px; color: var(--muted); }
.pill button:hover, .round:hover { color: var(--accent); }

.hint {
  padding: 8px var(--gutter) 12px;
  text-align: center;
  font-size: 17px;
  background: var(--bg);
  border-bottom: 1px solid var(--divider);
}

/* ---------- menu & settings ---------- */

.scroll { flex: 1; padding-bottom: calc(env(safe-area-inset-bottom) + 24px); }
.menu { padding-left: var(--gutter); padding-right: var(--gutter); }
.menu h2 {
  margin: 26px 20px 10px;
  font-size: 18px;
  font-weight: 650;
  color: var(--muted);
}
.list {
  list-style: none;
  margin: 0;
  padding: 0;
  border-radius: 24px;
  background: var(--card);
  overflow: hidden;
}
.list li { position: relative; }
.list li + li::before {
  content: '';
  position: absolute;
  top: 0;
  left: 20px;
  right: 20px;
  border-top: 1px solid var(--divider);
}
.list a, .list button {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  min-height: 58px;
  padding: 0 20px;
  border: 0;
  background: none;
  color: var(--text);
  font: inherit;
  font-size: 18px;
  text-align: left;
  text-decoration: none;
  cursor: pointer;
}
.list a:hover, .list button:hover { background: rgba(255, 255, 255, .04); }
.chev, .tick { color: var(--accent); display: grid; }
.chev svg { width: 22px; height: 22px; }
.tick svg { width: 26px; height: 26px; }
.foot { margin: 22px 20px; color: var(--muted); font-size: 14px; }

/* ---------- calculator ---------- */

.rows { display: flex; flex-direction: column; }
.row {
  display: grid;
  grid-template-columns: minmax(110px, 36%) 1fr;
  align-items: center;
  gap: 12px;
  padding: 12px var(--gutter) 12px 10px;
  background: var(--row);
  border-bottom: 2px solid var(--divider);
}
.row:nth-child(even) { background: var(--row-alt); }

.diagram {
  width: 100%;
  max-height: 64px;
  overflow: visible;
  stroke-width: 1.3;
  stroke-linejoin: round;
  stroke-linecap: round;
  fill: none;
}

input[data-key] {
  width: 100%;
  min-width: 0;
  height: 64px;
  padding: 0 14px;
  border: 2px solid transparent;
  border-radius: 2px;
  background: var(--field);
  color: var(--field-text);
  font: inherit;
  font-size: clamp(20px, 5.4vw, 28px);
  outline: none;
}
input[data-key]::placeholder { color: var(--placeholder); }
input[data-key]:focus { border-color: var(--accent); }
input[data-key].computed { color: var(--accent); font-weight: 600; }
input[data-key].bad { border-color: var(--error); }

.cell { display: flex; flex-direction: column; gap: 8px; min-width: 0; }
.chips { display: flex; gap: 8px; }
.chips button {
  flex: 1;
  min-height: 36px;
  border: 1px solid var(--accent);
  border-radius: 18px;
  background: none;
  color: var(--accent);
  font: inherit;
  font-size: 15px;
  cursor: pointer;
}
.chips button:hover { background: var(--accent); color: #fff; }

.section {
  padding: 18px var(--gutter) 12px;
  text-align: center;
  border-bottom: 2px solid var(--divider);
}
.section h2 { margin: 0; font-size: 18px; font-weight: 650; }
.section p { margin: 4px 0 0; color: var(--muted); font-size: 15px; }
.msg.sub { margin-bottom: 4px; }

.tiles {
  display: grid;
  grid-template-columns: 1fr 1fr;
  background: var(--row);
  border-bottom: 2px solid var(--divider);
}
.tile {
  display: grid;
  grid-template-columns: 34% 1fr;
  align-items: center;
  gap: 10px;
  padding: 14px 10px;
  min-height: 82px;
}
.tile + .tile { border-left: 2px solid var(--divider); }
.tile .diagram { max-height: 40px; }
output {
  color: var(--muted);
  font-size: clamp(18px, 5vw, 26px);
  overflow-wrap: anywhere;
}
output.has-value { color: var(--accent); font-weight: 600; }
output.has-value::before {
  content: attr(data-label);
  display: block;
  color: var(--muted);
  font-size: 13px;
  font-weight: 400;
}
.out-row output { padding-left: 4px; }

.msg { min-height: 24px; margin: 14px var(--gutter) 0; text-align: center; color: var(--muted); font-size: 15px; }
.msg.error { color: var(--error); }
.msg.info { color: var(--text); }
.msg button {
  margin-left: 6px;
  padding: 6px 12px;
  border: 1px solid var(--accent);
  border-radius: 14px;
  background: none;
  color: var(--accent);
  font: inherit;
  cursor: pointer;
}
.units {
  display: block;
  margin: 18px auto 0;
  width: fit-content;
  color: var(--muted);
  font-size: 13px;
  text-decoration: none;
}
.units:hover { color: var(--accent); }

.toast {
  position: fixed;
  left: 50%;
  bottom: calc(env(safe-area-inset-bottom) + 32px);
  transform: translateX(-50%);
  padding: 10px 20px;
  border-radius: 20px;
  background: var(--accent);
  color: #fff;
  font-weight: 600;
  z-index: 20;
}

/* Wider screens (tablets, PC): a bit more air around the diagrams. */
@media (min-width: 700px) {
  .row { grid-template-columns: 240px 1fr; padding-left: 24px; }
  .diagram { max-height: 72px; }
  input[data-key] { font-size: 26px; }
}

.msg.sub:empty { display: none; }

.section-head { display: grid; grid-template-columns: 1fr auto 1fr; align-items: center; gap: 8px; }
.section-head h2 { grid-column: 2; }
.sec-clear {
  grid-column: 3;
  justify-self: end;
  display: flex;
  align-items: center;
  gap: 4px;
  padding: 6px 12px 6px 8px;
  border: 1px solid var(--divider);
  border-radius: 16px;
  background: var(--row);
  color: var(--muted);
  font: inherit;
  font-size: 14px;
  cursor: pointer;
}
.sec-clear svg { width: 18px; height: 18px; }
.sec-clear:hover { color: var(--accent); border-color: var(--accent); }

/* Diagram with a short label beside it (e.g. OD, Thk). */
.diag { display: flex; align-items: center; gap: 8px; min-width: 0; }
.diag .diagram { flex: 1; min-width: 0; }
.abbr {
  flex: 0 0 58px;
  font-size: 15px;
  font-weight: 650;
  line-height: 1.15;
  text-align: center;
  color: var(--text);
}