/* Theme: Botanical Garden — Fern Green #4a7c59 · Marigold #f9a620 · Terracotta #b7472a · Cream #f5f3ed
   Headers: DejaVu Serif Bold · Body: DejaVu Sans (with widely available fallbacks) */
:root {
  --fern: #4a7c59;
  --fern-dark: #335540;
  --marigold: #f9a620;
  --terracotta: #b7472a;
  --cream: #f5f3ed;

  --bg: var(--cream);
  --panel: #fffdf8;
  --fg: #26301f;
  --muted: #6a6f5c;
  --line: #ddd8c6;
  --accent: var(--fern);
  --accent-dark: var(--fern-dark);
  --accent-soft: #e2ece3;
  --pivot: #fde4ac;
  --err: var(--terracotta);
  --err-soft: #f7e1d9;
  --ok: #2f6b43;
  --ok-soft: #dcecdf;
  --warn: #7a4a00;
  --warn-soft: #fdecc8;
  --shadow: 0 1px 2px rgba(51, 85, 64, .08), 0 2px 8px rgba(51, 85, 64, .06);
  --mono: "JetBrains Mono", "Cascadia Code", Consolas, "SF Mono", Menlo, monospace;
  --serif: "DejaVu Serif", Georgia, "Times New Roman", serif;
  --sans: "DejaVu Sans", Verdana, system-ui, -apple-system, "Segoe UI", sans-serif;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: var(--sans);
  background: var(--bg);
  color: var(--fg);
  line-height: 1.5;
}
h1, h2, h3 { font-family: var(--serif); }
header {
  padding: 26px 24px 22px;
  background: linear-gradient(135deg, var(--fern-dark), var(--fern));
  color: var(--cream);
  border-bottom: 4px solid var(--marigold);
}
header h1 { margin: 0; font-size: 28px; font-weight: 700; letter-spacing: .2px; }
header .sub { margin: 6px 0 0; color: #dfe9de; font-size: 14px; }
header code { background: rgba(245, 243, 237, .16); color: var(--cream); }
code { font-family: var(--mono); background: var(--accent-soft); padding: 0 4px; border-radius: 4px; }
header .title-row { display: flex; align-items: center; justify-content: space-between; gap: 12px; }
.ghost-light {
  background: rgba(245, 243, 237, .14); color: var(--cream); border-color: rgba(245, 243, 237, .4);
  font-size: 13px; padding: 4px 12px;
}
.ghost-light:hover { background: rgba(245, 243, 237, .26); color: #fff; border-color: var(--cream); }

/* ---------- layout + settings sidebar ---------- */
.layout { display: grid; grid-template-columns: 290px minmax(0, 1fr); gap: 0; align-items: start; }
body.side-collapsed .layout { grid-template-columns: minmax(0, 1fr); }
body.side-collapsed .sidebar { display: none; }
main { padding: 20px 24px 48px; min-width: 0; max-width: 1400px; }
.sidebar {
  position: sticky; top: 0; align-self: start; max-height: 100vh; overflow-y: auto;
  margin: 20px 0 20px 24px; padding: 6px 0;
  background: var(--panel); border: 1px solid var(--line); border-top: 3px solid var(--marigold);
  border-radius: 10px; box-shadow: var(--shadow); font-size: 14px;
}
.side-section { margin: 0; border-bottom: 1px solid var(--line); }
.side-section > summary {
  list-style: none; cursor: pointer; padding: 10px 16px; display: flex; align-items: center; justify-content: space-between;
  font-family: var(--serif); font-weight: 700; font-size: 14px; color: var(--fern-dark);
}
.side-section > summary::-webkit-details-marker { display: none; }
.side-section > summary::after { content: "▾"; color: var(--muted); transition: transform .15s; }
.side-section:not([open]) > summary::after { transform: rotate(-90deg); }
.side-section > summary:hover { background: var(--accent-soft); }
.side-body { padding: 2px 16px 14px; display: flex; flex-direction: column; gap: 8px; }
.side-body label { display: flex; flex-direction: column; align-items: flex-start; gap: 4px; }
.side-body select, .side-body input[type=text] { width: 100%; }
.side-body input[type=number] { width: 70px; }
.side-body .note { margin: 0; color: var(--muted); font-size: 12px; }
.side-actions { padding: 12px 16px 8px; }
.side-actions button { width: 100%; }
#assign-note { font-family: var(--mono); font-size: 12px; word-break: break-word; }
.sidebar .helptable { font-size: 12px; }
.sidebar .helptable td { display: block; padding: 0; }
.sidebar .helptable tr { display: block; margin-bottom: 6px; }
.sidebar .helptable .math { word-break: break-word; }

/* ---------- inputs ---------- */
.inputs { display: flex; flex-wrap: wrap; gap: 16px; }
.matrix-panel {
  background: var(--panel);
  border: 1px solid var(--line);
  border-top: 3px solid var(--fern);
  border-radius: 10px;
  box-shadow: var(--shadow);
  padding: 14px 16px;
  flex: 1 1 380px;
  min-width: 0;
}
.matrix-panel .head { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; margin-bottom: 10px; }
.matrix-panel h2 { margin: 0; font-size: 18px; font-weight: 700; color: var(--fern-dark); }
.matrix-panel .dims { display: flex; align-items: center; gap: 6px; color: var(--muted); font-size: 14px; }
.matrix-panel .dims input { width: 54px; }
input[type=number], input[type=text], select {
  font: inherit; padding: 4px 6px; border: 1px solid var(--line); border-radius: 6px; background: #fff; color: var(--fg);
}
input[type=number]:focus, input[type=text]:focus, select:focus { outline: 2px solid var(--marigold); border-color: transparent; }
.grid-wrap { overflow-x: auto; padding: 4px 0; }
.grid { display: inline-grid; gap: 4px; }
.grid input {
  width: 64px; text-align: center; font-family: var(--mono); font-size: 14px; padding: 5px 4px;
}
.grid input:focus { outline: 2px solid var(--marigold); border-color: transparent; }
.grid input.bad { border-color: var(--err); background: var(--err-soft); }
.matrix-panel .tools { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 10px; }

/* ---------- buttons ---------- */
button {
  font: inherit; font-size: 14px; padding: 6px 12px; border-radius: 7px; border: 1px solid var(--line);
  background: #fff; color: var(--fg); cursor: pointer; transition: background .12s, color .12s, border-color .12s;
}
button:hover { border-color: var(--fern); color: var(--fern-dark); background: var(--accent-soft); }
button:focus-visible { outline: 2px solid var(--marigold); outline-offset: 1px; }
button.small { font-size: 12px; padding: 3px 8px; }
button.ghost { background: transparent; }
.ops { margin-top: 18px; display: grid; grid-template-columns: repeat(auto-fit, minmax(290px, 1fr)); gap: 16px; align-items: start; }
.op-group {
  background: var(--panel); border: 1px solid var(--line); border-radius: 10px; box-shadow: var(--shadow);
  padding: 12px 16px 14px;
}
.op-group h3 { margin: 0 0 6px; font-size: 15px; color: var(--fern-dark); font-weight: 700; display: flex; align-items: center; flex-wrap: wrap; gap: 8px; }
.op-group h3 .hint { font-family: var(--sans); font-size: 12px; font-weight: 400; color: var(--muted); margin-left: auto; }
.sublabel {
  display: flex; align-items: center; gap: 8px; margin: 10px 0 5px;
  font-size: 11px; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--muted);
}
.sublabel::after { content: ""; flex: 1; height: 1px; background: var(--line); }
.sublabel .seg { order: 1; text-transform: none; letter-spacing: 0; }
.sublabel::after { order: 2; }
.op-group .btns { display: flex; flex-wrap: wrap; gap: 6px; }
.op-group .btns button { background: var(--accent-soft); border-color: transparent; color: var(--fern-dark); font-weight: 500; }
.op-group .btns button:hover { background: var(--fern); color: #fff; }
.seg button { border-radius: 0; padding: 2px 10px; font-size: 13px; font-family: var(--sans); font-weight: 500; }
.seg button:first-child { border-radius: 6px 0 0 6px; }
.seg button:last-child { border-radius: 0 6px 6px 0; margin-left: -1px; }
.seg button.active { background: var(--fern-dark); color: #fff; border-color: var(--fern-dark); }
.seg button.active:hover { background: var(--fern-dark); color: #fff; }

/* ---------- results ---------- */
#results { margin-top: 20px; display: flex; flex-direction: column; gap: 14px; }
.card {
  background: var(--panel); border: 1px solid var(--line); border-left: 4px solid var(--fern);
  border-radius: 10px; box-shadow: var(--shadow); padding: 14px 18px;
}
.card h2 { margin: 0 0 8px; font-size: 17px; font-weight: 700; color: var(--fern-dark); }
.card .row { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; margin: 6px 0; }
.card .op { font-size: 20px; color: #a35f00; font-weight: 700; padding: 0 4px; }   /* deep marigold: readable on cream */
.card p { margin: 6px 0; }
.card .note { color: var(--muted); font-size: 14px; }
.card.error { border-color: var(--err); border-left-color: var(--err); background: var(--err-soft); color: var(--err); }
.card.error h2 { color: var(--err); }
.badge { display: inline-block; padding: 1px 8px; border-radius: 999px; font-size: 12px; font-weight: 600; }
.badge.ok { background: var(--ok-soft); color: var(--ok); }
.badge.no { background: var(--err-soft); color: var(--err); }
.label { font-weight: 600; margin-right: 4px; }
.big { font-size: 20px; font-family: var(--mono); }
.math { font-family: var(--mono); }
details { margin-top: 8px; }
summary { cursor: pointer; color: var(--fern); font-weight: 600; }
summary:hover { color: var(--fern-dark); }
.steps { display: flex; flex-wrap: wrap; gap: 14px; margin-top: 8px; }
.step { border: 1px dashed #c9c3ac; border-radius: 8px; padding: 6px 10px; background: #fffcf3; }
.step .desc { font-family: var(--mono); font-size: 13px; color: var(--muted); margin-bottom: 4px; }
.subspace { border-top: 1px solid var(--line); padding-top: 8px; margin-top: 8px; }
.subspace h3 { margin: 0 0 4px; font-size: 15px; font-weight: 700; color: var(--fern-dark); }
.eig { border-top: 1px solid var(--line); padding-top: 8px; margin-top: 8px; }
.eig .row { align-items: flex-start; }

/* matrix with brackets */
.matwrap { display: inline-flex; flex-direction: column; align-items: center; gap: 4px; }
.mat { display: inline-block; padding: 2px 4px; }
.mat .katex { font-size: 1.12em; color: var(--fg); }
/* typeset math */
.tex { color: var(--fg); }
.tex .katex { font-size: 1.08em; }
.tex-line { display: inline-block; vertical-align: middle; margin: 2px 0; }
.big .tex-line .katex { font-size: 1.35em; }
.cap .tex .katex, .desc .tex .katex { font-size: 1em; }
.katex-error { color: var(--err); font-family: var(--mono); font-size: 13px; }
.matwrap .cap { font-size: 12px; color: var(--muted); }
.matwrap .send { display: flex; gap: 4px; }
.vecs { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
.trivial { font-family: var(--mono); }

/* ---------- symbolic additions ---------- */
.matrix-panel .varnote { color: var(--terracotta); font-size: 12px; font-family: var(--mono); margin-left: auto; }
.grid input { width: 64px; min-width: 64px; }
#assign.bad { border-color: var(--err); background: var(--err-soft); }
.badge.warn { background: var(--warn-soft); color: var(--warn); }
.note.approx { color: var(--muted); font-family: var(--mono); }
.note.assume { background: #fff8e4; border-left: 3px solid var(--marigold); padding: 6px 10px; border-radius: 0 6px 6px 0; }
.helptable { border-collapse: collapse; margin: 6px 0; font-size: 13px; }
.helptable td { padding: 2px 14px 2px 0; vertical-align: top; }
.helptable td:first-child { color: var(--muted); white-space: nowrap; }

@media (max-width: 900px) {
  .layout { grid-template-columns: minmax(0, 1fr); }
  .sidebar { position: static; max-height: none; margin: 16px 12px 0; }
}
@media (max-width: 600px) {
  header { padding: 18px 16px 16px; }
  header h1 { font-size: 23px; }
  main { padding: 16px 12px 40px; }
}