/* ═══════════════════════════════════════════════════════════════
   SDresources practicals: lab-book styles
   One stylesheet for every practical page and hub (GCSE, AS, A2).
   Paper, ruled tables, graph paper and a biro-blue pen. Sentence
   case throughout: units are never transformed, so mm stays mm.
═══════════════════════════════════════════════════════════════ */

:root {
  /* Colours match the sdresources home page: #F5F5F0 / #111110 /
     #888880 / #DDDDD8 / #2B5CE6. ink-2 is a darker step of the same
     grey so small text keeps enough contrast on the paper colour. */
  --paper: #F5F5F0;
  --sheet: #FFFFFF;
  --ink: #111110;
  --ink-2: #5F5F58;
  --ink-3: #888880;
  --rule: #DDDDD8;
  --rule-2: #EBEBE6;
  --pen: #2B5CE6;
  --pen-light: #EEF2FD;
  --red: #C0392B;
  --red-light: #FBEAE8;
  --green: #1E8E5A;
  --grid-minor: #E8EDFB;
  --grid-major: #C5D3F6;
  --lcd-bg: #111110;
  --lcd-fg: #F5F5F0;
  --font: 'Atkinson Hyperlegible', 'Segoe UI', system-ui, -apple-system, sans-serif;
  --mono: 'IBM Plex Mono', ui-monospace, 'Cascadia Mono', Consolas, monospace;

  /* Names used inside the apparatus drawings. */
  --bg: var(--paper);
  --text: var(--ink);
  --muted: var(--ink-3);
  --border: var(--rule);
  --accent: var(--pen);
  --accent-light: var(--pen-light);
  --danger: var(--red);
  --danger-light: var(--red-light);
  --ok: var(--green);
}

* { box-sizing: border-box; }
body { margin: 0; background: var(--paper); color: var(--ink); font-family: var(--font); font-size: 16px; line-height: 1.5; }
a { color: var(--pen); }
.visually-hidden { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

.lab, .hub { max-width: 1060px; margin: 0 auto; padding: 0 20px; }

/* ── Top bar and practical switcher ── */
.lab-top { display: flex; align-items: center; gap: 8px 18px; flex-wrap: wrap; padding: 14px 0; border-bottom: 1px solid var(--rule); font-size: 14.5px; }
.lab-site { font-weight: 700; color: var(--ink); text-decoration: none; }
.lab-site span { color: var(--pen); }
.lab-crumbs { flex: 1; color: var(--ink-2); }
.lab-crumbs a { color: var(--ink-2); }
.lab-switch { display: flex; align-items: center; justify-content: space-between; gap: 10px 16px; flex-wrap: wrap; padding: 10px 0; border-bottom: 1px solid var(--rule); font-size: 14.5px; }
.lab-switch label { display: flex; align-items: center; gap: 8px; flex: 1 1 320px; min-width: 0; justify-content: center; }
.lab-switch select { font: inherit; padding: 6px 8px; border: 1px solid var(--ink-3); background: var(--sheet); color: var(--ink); width: 100%; min-width: 0; flex: 1 1 0; text-overflow: ellipsis; }
@media (max-width: 600px) {
  .lab-switch { flex-direction: column; align-items: stretch; }
  .lab-switch label { flex: 1 1 auto; width: 100%; }
  .lab-next { text-align: left; }
}
.lab-prev, .lab-next { color: var(--ink-2); text-decoration: none; }
.lab-prev:hover, .lab-next:hover { color: var(--ink); text-decoration: underline; }
.lab-next { text-align: right; }

/* ── Title ── */
.lab-title { padding: 26px 0 4px; }
.lab-ref { margin: 0 0 4px; font-family: var(--mono); font-size: 13.5px; color: var(--ink-2); }
.lab-title h1 { margin: 0; font-size: clamp(26px, 4vw, 36px); line-height: 1.15; }
.lab-aim { margin: 12px 0 0; max-width: 72ch; }

/* ── Parts (e.g. liquid / solid) ── */
.lab-parts { display: flex; flex-wrap: wrap; margin-top: 22px; border-bottom: 1px solid var(--rule); }
.lab-parts button { font: inherit; background: none; border: 1px solid transparent; border-bottom: none; margin-bottom: -1px; padding: 8px 14px; cursor: pointer; color: var(--ink-2); }
.lab-parts button[aria-selected="true"] { background: var(--sheet); border-color: var(--rule); color: var(--ink); font-weight: 700; }

/* ── Sections ── */
.lab-sec { margin-top: 36px; }
.lab-sec > h2 { display: flex; align-items: baseline; gap: 10px; margin: 0 0 14px; padding-bottom: 6px; border-bottom: 2px solid var(--ink); font-size: 21px; }
.lab-sec > h2 .n { font-family: var(--mono); font-size: 15px; font-weight: 600; min-width: 1.3em; }
.lab-hint { margin: 0; color: var(--ink-2); max-width: 72ch; }

/* ── Apparatus bench ── */
.lab-bench { display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr); gap: 24px; align-items: start; }
@media (max-width: 820px) { .lab-bench { grid-template-columns: 1fr; } }
.lab-figure { margin: 0; background: var(--sheet); border: 1px solid var(--rule); padding: 12px; }
.lab-diagram svg { display: block; width: 100%; height: 270px; }
@media (max-width: 600px) { .lab-diagram svg { height: 220px; } }
.lab-status { margin-top: 8px; min-height: 1.5em; font-size: 14.5px; color: var(--ink-2); }
.lab-status .flag { color: var(--red); font-weight: 700; }
.lab-status .good { color: var(--green); font-weight: 700; }

.lab-controls { display: flex; flex-direction: column; gap: 18px; }
.ctl[hidden] { display: none; }
.ctl > label, .ctl .ctl-label { display: block; margin-bottom: 6px; font-size: 15px; font-weight: 700; }
.ctl-row { display: flex; align-items: center; gap: 12px; }
.ctl-row input[type="range"] { flex: 1; min-width: 0; accent-color: var(--ink); }
.ctl-val { min-width: 8ch; padding: 3px 7px; border: 1px solid var(--rule); background: var(--sheet); font-family: var(--mono); font-size: 15px; text-align: right; white-space: nowrap; }
.ctl select { width: 100%; padding: 8px; border: 1px solid var(--ink-3); background: var(--sheet); color: var(--ink); font: inherit; }
.ctl-note { margin: 6px 0 0; font-size: 14px; color: var(--ink-2); }
.ctl-readout { display: flex; justify-content: space-between; align-items: baseline; gap: 12px; padding: 8px 12px; background: var(--lcd-bg); color: var(--lcd-fg); font-family: var(--mono); font-size: 17px; }
.ctl-readout span { font-family: var(--font); font-size: 14px; color: #A8A8A0; }
.ctl-fixed { margin: 0; padding-left: 10px; border-left: 3px solid var(--rule); font-size: 14.5px; color: var(--ink-2); }
.slots { display: flex; gap: 6px; margin: 6px 0 8px; }
.slot { flex: 1; padding: 5px 4px; border: 1px dashed var(--ink-3); font-family: var(--mono); font-size: 13.5px; text-align: center; color: var(--ink-3); }
.slot.filled { border-style: solid; background: var(--sheet); color: var(--ink); }
.lab-method { margin-top: 18px; }
.lab-method summary, .lab-notes summary { cursor: pointer; font-weight: 700; }
.lab-method ol { margin: 8px 0 0; padding-left: 22px; max-width: 72ch; }
.lab-method li { margin-bottom: 4px; }

/* ── Buttons ── */
.btn { padding: 8px 14px; border: 1px solid var(--ink); border-radius: 2px; background: var(--sheet); color: var(--ink); font: inherit; font-size: 15px; cursor: pointer; }
.btn:hover { background: var(--rule-2); }
.btn:disabled { opacity: 0.45; cursor: not-allowed; }
.btn:disabled:hover { background: var(--sheet); }
.btn-primary { background: var(--ink); color: #fff; }
.btn-primary:hover { background: #000; }
.btn-primary:disabled:hover { background: var(--ink); }
.btn-quiet { border-color: var(--rule); color: var(--ink-2); }
.btn-danger { border-color: var(--red); color: var(--red); }
.btn-row { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 12px; }
@media (pointer: coarse) { .btn, .ctl select, .lab-switch select { min-height: 44px; } }

/* ── Results table ── */
.lab-count { margin: 0 0 10px; font-size: 14.5px; color: var(--ink-2); }
.lab-table-wrap { overflow-x: auto; background: var(--sheet); border: 1px solid var(--rule); }
table.lab-table { width: 100%; border-collapse: collapse; }
.lab-table th { padding: 8px 12px; border-bottom: 2px solid var(--ink); font-size: 15px; text-align: right; white-space: nowrap; }
.lab-table td { padding: 6px 12px; border-bottom: 1px solid var(--rule-2); font-family: var(--mono); font-size: 14.5px; text-align: right; white-space: nowrap; }
.lab-table th:first-child, .lab-table td:first-child { text-align: left; color: var(--ink-3); }
.lab-table .derived { color: var(--pen); }
.lab-table tbody tr { cursor: pointer; }
.lab-table tbody tr:hover td { background: #FAFAF7; }
.lab-table tr.selected td { background: var(--pen-light); }
.row-del { padding: 0 4px; border: none; background: none; color: var(--ink-3); font-size: 19px; line-height: 1; cursor: pointer; }
.row-del:hover { color: var(--red); }
.lab-empty { margin: 0; padding: 14px; color: var(--ink-2); }

/* ── Graph ── */
.graph-tabs { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 10px; }
.graph-tabs button { padding: 4px 10px; border: 1px solid var(--rule); background: var(--sheet); font: inherit; font-size: 14px; cursor: pointer; }
.graph-tabs button[aria-pressed="true"] { border-color: var(--ink); font-weight: 700; }
.graph-sheet { padding: 8px; background: var(--sheet); border: 1px solid var(--rule); }
.graph-plot svg { display: block; width: 100%; height: auto; }
.graph-caption { margin: 8px 0 0; font-size: 14.5px; color: var(--ink-2); max-width: 72ch; }
.plot .tick { font-family: var(--mono); font-size: 11px; fill: var(--ink-2); }
.plot .axis-label { font-family: var(--font); font-size: 13px; font-weight: 700; fill: var(--ink); }
.plot .legend { font-family: var(--font); font-size: 12.5px; fill: var(--ink); }
.plot .mark-label { font-family: var(--mono); font-size: 12px; font-weight: 600; fill: var(--red); }

/* ── Analysis ── */
ol.steps { margin: 0; padding: 0; list-style: none; counter-reset: step; }
ol.steps li { counter-increment: step; margin-bottom: 10px; padding: 10px 14px; background: var(--sheet); border: 1px solid var(--rule); border-left: 3px solid var(--ink); }
.step-label { margin: 0; font-weight: 700; }
.step-label::before { content: "Step " counter(step) ".  "; font-family: var(--mono); font-size: 14px; font-weight: 600; color: var(--ink-2); }
.step-work { margin: 6px 0 0; font-family: var(--mono); font-size: 14.5px; white-space: pre-wrap; }
.step-val { margin: 6px 0 0; font-weight: 700; }
.try { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; margin: 4px 0 4px; font-size: 15px; }
.try input { width: 11ch; padding: 6px; border: 1px solid var(--ink-3); font-family: var(--mono); font-size: 15px; }
.try .ok { color: var(--green); font-weight: 700; }
.try .no { color: var(--red); font-weight: 700; }

/* ── Theory and evaluation ── */
.lab-notes details { padding: 10px 0; border-top: 1px solid var(--rule); }
.lab-notes details:last-child { border-bottom: 1px solid var(--rule); }
.lab-notes p, .lab-notes ul { margin: 8px 0 0; max-width: 72ch; }
.lab-notes li { margin-bottom: 4px; }

/* ── Take reading bar ── */
.lab-bar { position: sticky; bottom: 0; z-index: 30; display: flex; align-items: center; gap: 14px; margin-top: 36px; padding: 10px 0 calc(10px + env(safe-area-inset-bottom, 0px)); border-top: 1px solid var(--ink); background: var(--paper); }
.lab-bar .btn-primary { min-height: 46px; padding: 0 22px; font-size: 16px; font-weight: 700; }
.lab-bar-msg { font-size: 14.5px; color: var(--ink-2); }
@media (max-width: 600px) { .lab-bar .btn-primary { flex: 0 0 auto; } }

.lab-foot { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 6px; padding: 22px 0 34px; font-size: 14px; color: var(--ink-2); }

/* ── Toast ── */
.toast { position: fixed; left: 50%; bottom: 84px; z-index: 1100; max-width: 90vw; padding: 9px 16px; background: var(--ink); color: #fff; font-size: 14.5px; opacity: 0; pointer-events: none; transform: translateX(-50%); transition: opacity 0.2s; }
.toast.show { opacity: 1; }
.toast.error { background: var(--red); }

/* ── Hubs ── */
.hub h1 { margin: 30px 0 6px; font-size: clamp(30px, 5vw, 44px); line-height: 1.1; }
.hub-intro { margin: 0; max-width: 70ch; color: var(--ink-2); }
.hub-group { margin-top: 32px; }
.hub-group h2 { display: flex; align-items: baseline; gap: 10px; margin: 0; padding-bottom: 6px; border-bottom: 2px solid var(--ink); font-size: 19px; }
.hub-group h2 .n { font-family: var(--mono); font-size: 15px; font-weight: 600; }
.hub-group h2 small { margin-left: auto; font-size: 14px; font-weight: 400; color: var(--ink-2); }
.hub-list { margin: 0; padding: 0; list-style: none; }
.hub-list a, .hub-list .soon { display: grid; grid-template-columns: 6.5em 1fr auto; gap: 4px 16px; align-items: baseline; padding: 12px 4px; border-bottom: 1px solid var(--rule); color: var(--ink); text-decoration: none; }
.hub-list a:hover { background: var(--sheet); }
.hub-code { font-family: var(--mono); font-size: 14px; color: var(--ink-2); }
.hub-name { font-weight: 700; }
.hub-sum { display: block; font-weight: 400; font-size: 14.5px; color: var(--ink-2); }
.hub-go { color: var(--pen); font-size: 14.5px; white-space: nowrap; }
.hub-list .soon .hub-name, .hub-list .soon .hub-go { color: var(--ink-3); }
@media (max-width: 600px) {
  .hub-list a, .hub-list .soon { grid-template-columns: 1fr auto; }
  .hub-code { grid-column: 1 / -1; }
}
.hub-foot { margin-top: 36px; }