/* T.08 matrix calculator — shared lab-notebook look. */
:root, [data-theme="dark"] {
    --bg: #0b0d0c; --surface: #131716; --surface2: #191f1d;
    --line: #26302b; --line-soft: #1c2320;
    --ink: #e9eee6; --muted: #a9b4a9; --faint: #6e7a71;
    --lime: #c8f04b; --lime-ink: #1a2005; --amber: #ffa14a; --red: #ff6f6f;
    --serif: "Newsreader", Georgia, serif;
    --mono: "JetBrains Mono", ui-monospace, Menlo, Consolas, monospace;
    --sans: system-ui, -apple-system, "Segoe UI", Arial, sans-serif;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
body { font-family: var(--sans); background: var(--bg); color: var(--ink); line-height: 1.6; font-size: 16px; -webkit-font-smoothing: antialiased; }
.wrap { max-width: 1080px; margin: auto; padding: 0 28px; }
.skip-link { position: absolute; left: -9999px; top: 0; background: var(--lime); color: var(--lime-ink); padding: 10px 16px; border-radius: 0 0 8px 0; z-index: 50; font-family: var(--mono); font-size: 0.85rem; }
.skip-link:focus { left: 0; }
.topbar { border-bottom: 1px solid var(--line); padding: 14px 0; }
.topbar-inner { display: flex; justify-content: space-between; align-items: center; }
.back { font-family: var(--mono); font-size: 0.85rem; text-decoration: none; color: var(--muted); }
.back:hover { color: var(--lime); }
.tool-tag { font-family: var(--mono); font-size: 0.75rem; color: var(--faint); text-transform: uppercase; letter-spacing: 0.1em; }
.head { padding: 40px 0 26px; }
h1 { font-family: var(--serif); font-size: clamp(2.2rem, 5vw, 3.2rem); letter-spacing: -0.02em; line-height: 1.05; }
h1 em { font-style: italic; color: var(--lime); }
.sub { color: var(--muted); margin-top: 8px; max-width: 62ch; }
h2 { font-family: var(--mono); font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.14em; color: var(--faint); margin-bottom: 10px; }
h2.mt { margin-top: 20px; }
.grid { display: grid; grid-template-columns: 1fr 1.2fr; gap: 22px; padding-bottom: 30px; }
.panel { background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 26px; align-self: start; }
.panel.accent { border-top: 3px solid var(--lime); }
.label-row { display: flex; justify-content: space-between; align-items: center; margin-bottom: 8px; }
.label-row h2 { margin: 0; }
.hint-inline { font-family: var(--mono); font-size: 0.75rem; color: var(--faint); }
textarea { width: 100%; font-family: var(--mono); font-size: 0.95rem; background: var(--bg); color: var(--ink); border: 1px solid var(--line); border-radius: 10px; padding: 14px; resize: vertical; }
textarea:focus { outline: 2px solid var(--lime); outline-offset: 1px; }
.row { display: flex; gap: 10px; margin-top: 12px; flex-wrap: wrap; }
.row.between { justify-content: space-between; }
.btn { font-family: var(--mono); font-size: 0.85rem; padding: 11px 18px; border-radius: 9px; border: 1px solid var(--line); background: transparent; color: var(--ink); cursor: pointer; }
.btn:hover { border-color: var(--lime); color: var(--lime); }
.btn.sm { padding: 8px 14px; font-size: 0.8rem; }
.ops { display: flex; gap: 8px; flex-wrap: wrap; }
.ops .op.active { border-color: var(--lime); color: var(--lime); }
.empty { color: var(--faint); font-size: 0.92rem; padding: 14px 4px; }
.err { color: var(--red); font-family: var(--mono); font-size: 0.85rem; }
.mat { border-collapse: collapse; margin: 6px 0 4px; font-family: var(--mono); font-size: 0.95rem; }
.mat td { border: 1px solid var(--line); padding: 8px 14px; text-align: right; font-variant-numeric: tabular-nums; }
.scalar { font-family: var(--serif); font-size: 2rem; color: var(--lime); }
.step { border-left: 3px solid var(--line); padding: 8px 0 8px 14px; margin: 12px 0; }
.step p { font-family: var(--mono); font-size: 0.78rem; color: var(--amber); margin-bottom: 6px; }
.step .mat td { padding: 5px 10px; font-size: 0.82rem; }
.foot { padding: 18px 28px 40px; font-family: var(--mono); font-size: 0.75rem; color: var(--faint); }
@media (max-width: 860px) { .grid { grid-template-columns: 1fr; } }