/* Motion Graphs: its colours, diagrams, drawing editor and tutor marks; the general look is in
   ui.css (shared by the apps). */
:root {
  --grid: #ebe8e1;
  --grid-major: #d9d5cb;
  /* one colour per quantity */
  --q-s: #c62828;
  --q-v: #1f5fc4;
  --q-a: #1b7f3b;
  --band: #fdf0c4;
  --focus-band: rgba(43, 89, 195, 0.1);
  --area-pos: rgba(43, 89, 195, 0.22);
  --area-neg: rgba(194, 65, 12, 0.24);
}

@media (prefers-color-scheme: dark) {
  :root {
    --grid: #2a2e33;
    --grid-major: #3a3f45;
    --q-s: #ff7b72;
    --q-v: #79a8ff;
    --q-a: #5fd07e;
    --band: #3a3320;
    --focus-band: rgba(122, 162, 255, 0.12);
    --area-pos: rgba(122, 162, 255, 0.28);
    --area-neg: rgba(251, 146, 60, 0.28);
  }
}

.card h3 { margin: 18px 0 6px; }
.actions { margin-top: 16px; }

i.bar { text-decoration: overline; text-decoration-thickness: 1px; }

/* diagrams */
.qc-s { color: var(--q-s); }
.qc-v { color: var(--q-v); }
.qc-a { color: var(--q-a); }
.plot svg { display: block; width: 100%; height: auto; }
#draw { touch-action: none; user-select: none; -webkit-user-select: none; border-radius: 8px; }
#draw:focus { outline: none; }
#draw:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
#draw.dragging { cursor: grabbing !important; }
svg text { font-family: var(--serif); }
svg .grid { stroke: var(--grid); stroke-width: 1; }
svg .grid.major { stroke: var(--grid-major); }
svg .bp { stroke: var(--muted); stroke-width: 1; stroke-dasharray: 2 4; opacity: 0.7; }
svg .ax { stroke: var(--muted); stroke-width: 1.2; }
svg .tick { fill: var(--muted); font-size: 12px; font-family: system-ui, sans-serif; }
svg .axis { fill: var(--ink); font-size: 14px; }
svg .it { font-style: italic; }
svg .pnum { fill: var(--muted); font-size: 12px; font-weight: 600; font-family: system-ui, sans-serif; }
svg .pnum.bad { fill: var(--ink); }
svg .band { fill: var(--band); }
svg .qc-s { --qc: var(--q-s); }
svg .qc-v { --qc: var(--q-v); }
svg .qc-a { --qc: var(--q-a); }
svg .qlabel { fill: var(--qc); }
svg .curve { stroke: var(--qc); stroke-width: 2.6; fill: none; stroke-linecap: round; }
svg .curve.solution { stroke: var(--ink); stroke-width: 2; stroke-dasharray: 7 5; }
svg .handle { fill: var(--card); stroke: var(--qc); stroke-width: 2; }
svg .handle.mid { fill: var(--qc); fill-opacity: 0.25; }
svg .handle.active { fill: var(--qc); fill-opacity: 1; }
svg .fixed { fill: var(--muted); stroke: var(--card); stroke-width: 2; }
svg .hover { pointer-events: none; }
svg .guide { stroke: var(--qc); stroke-width: 1; stroke-dasharray: 3 3; opacity: 0.6; }
svg .gp { fill: var(--qc); }
svg .gp.on { fill: var(--card); stroke: var(--qc); stroke-width: 2; }
svg .val { fill: var(--ink); font-size: 13px; font-family: system-ui, sans-serif; font-weight: 600; paint-order: stroke; stroke: var(--card); stroke-width: 4px; }

.feedback { margin: 6px 0 0; padding-left: 1.2em; }
.feedback:empty { display: none; }
.feedback li { margin: 6px 0; }

#hint-list ul, .pieces { margin: 6px 0; padding-left: 1.2em; }
#sol-text p { margin: 8px 0; }
.pieces li { margin: 6px 0; }


/* tutor mode */
.tgraphs { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 8px 18px; }
.tgraphs h3 { margin: 4px 0 2px; font-size: 0.95rem; }
.tutor-text { min-height: 8em; }
.tutor-text p { margin: 8px 0; }
.tutor-text .step-rule { color: var(--muted); font-size: 0.9rem; font-weight: 600; margin-bottom: 4px; }
svg .band.focus { fill: var(--focus-band); }
.tgraphs svg .val { font-size: 19px; }
.tgraphs svg .tick, .tgraphs svg .pnum { font-size: 15px; }
/* stacked (tutor): each graph as wide as the page allows, so the usual label sizes */
.tgraphs.stack { grid-template-columns: minmax(0, 1fr); max-width: 760px; }
.tgraphs.stack svg .val { font-size: 13px; }
.tgraphs.stack svg .tick, .tgraphs.stack svg .pnum { font-size: 12px; }
svg .pnum.focus { fill: var(--ink); }
svg .chord { stroke: var(--ink); stroke-width: 1.4; stroke-dasharray: 6 4; }
svg .tangent { stroke: var(--ink); stroke-width: 2; stroke-linecap: round; }
svg .area.pos { fill: var(--area-pos); }
svg .area.neg { fill: var(--area-neg); }
svg .tdot { fill: var(--qc); stroke: var(--card); stroke-width: 1.5; }
svg .tdot.mean { fill: var(--card); stroke: var(--qc); stroke-width: 2; }
.k-band { background: var(--focus-band); border-radius: 3px; padding: 0 3px; }
.k-pos { background: var(--area-pos); border-radius: 3px; padding: 0 3px; }
.k-neg { background: var(--area-neg); border-radius: 3px; padding: 0 3px; }
@media (max-width: 760px) {
  .tgraphs { grid-template-columns: minmax(0, 1fr); }
}

/* arcade: manim's colours for s, v and a */
#arcade { --q-s: #fc6255; --q-v: #58c4dd; --q-a: #83c167; --grid: #1c1c1c; --grid-major: #333; --band: #222; }
#arcade #ar-figure .fig svg, #arcade .ar-explain > .figs .fig svg { width: 420px; }
#arcade #ar-figure .fig, #arcade .ar-explain > .figs .fig { flex: 0 1 420px; } /* full width on a phone */
#arcade .ar-opt { padding: 22px 8px 6px; }
#arcade .ar-opt .val { width: 100%; }
#arcade .ar-opt .val svg { width: 100%; max-width: 380px; margin: 0 auto; }
#arcade .ar-answers svg { width: 300px; display: block; }
#arcade .ar-explain .tgraphs { max-width: 760px; }
.ar-hero .figs .fig svg { width: 340px; }
/* the start picture: first the position, then its slope */
#ar-hero.animate .fig:nth-child(2) .curve { animation-delay: 1.4s, 1.8s; }

/* exercises answered by choosing and entering numbers (quiz.js) */
#q-fields { display: grid; gap: 18px; margin-bottom: 4px; }
.qprompt { margin: 0 0 8px; font-weight: 600; }
.qn {
  display: inline-grid; place-items: center; width: 1.5em; height: 1.5em; margin-right: 8px;
  border-radius: 50%; background: var(--accent); color: var(--accent-ink);
  font-size: 0.8rem; font-weight: 700; vertical-align: 1px;
}
.qopts { display: flex; flex-wrap: wrap; gap: 8px; }
.qopts.pics { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); }
.qopt { display: flex; align-items: center; gap: 8px; padding: 7px 12px; border: 1px solid var(--line); border-radius: 8px; background: var(--bg); cursor: pointer; }
.qopt input { margin: 0; accent-color: var(--accent); }
.qopts.pics .qopt { align-items: flex-start; padding: 6px; }
.qopts.pics .qval { flex: 1; min-width: 0; }
.qopts.pics .qval svg { display: block; width: 100%; height: auto; }
.qopt:hover { border-color: var(--accent); }
.qopt:has(input:checked) { border-color: var(--accent); box-shadow: 0 0 0 1px var(--accent) inset; background: var(--card); }
.qopts .qopt.right { border-color: var(--ok); background: var(--ok-bg); box-shadow: 0 0 0 1px var(--ok) inset; }
.qopts .qopt.wrong { border-color: var(--bad); background: var(--bad-bg); box-shadow: 0 0 0 1px var(--bad) inset; }
.qfb { margin: 8px 0 0; font-size: 0.93rem; }
.qfb:empty { display: none; }
.qfb.ok { color: var(--ok); }
.qfb.ok::before { content: "✓ "; }
.qfb.bad { color: var(--bad); }
.qfb.bad::before { content: "✗ "; }
.qblock .fields { margin-bottom: 0; }
@media (max-width: 560px) { .qopts.pics { grid-template-columns: minmax(0, 1fr); } }

/* their figures (figs.js): graphs of several motions, stroboscope picture, value table */
#q-figure .fig svg.cgraph, .steps .fig svg.cgraph, #t-figure .fig svg.cgraph { width: 420px; }
/* two graphs side by side (A and B): the pair takes the full row */
.figs.pair { flex: 1 1 100%; margin: 0; }
#q-figure .figs.pair .fig svg.cgraph, .steps .figs.pair .fig svg.cgraph, #t-figure .figs.pair .fig svg.cgraph, #arcade .figs.pair .fig svg.cgraph { width: 320px; }
svg.strobe { width: 480px; max-width: 100%; height: auto; display: block; }
.figs.pair figcaption, .fig figcaption { text-align: center; font-style: italic; color: var(--muted); }
svg .curve.dashed { stroke-dasharray: 9 6; }
svg .lname { fill: var(--ink); font: italic 600 15px var(--serif); paint-order: stroke; stroke: var(--card); stroke-width: 4px; stroke-linejoin: round; }
/* slope triangles: Δt along, Δs up or down */
svg .tri { fill: none; stroke: var(--ink); stroke-width: 1.4; stroke-dasharray: 4 3; }
svg .trilab { fill: var(--ink); font: 13px var(--serif); paint-order: stroke; stroke: var(--card); stroke-width: 4px; stroke-linejoin: round; }
/* a graph given as the answer in the tutor's summary: the size of the graphs above, not the page's */
.tutor-text p b svg { display: block; width: min(100%, 360px); height: auto; margin: 6px 0; }
svg .sdot { fill: var(--qc); stroke: var(--card); stroke-width: 1.5; }
svg .stime { fill: var(--ink); font: 600 11px system-ui, sans-serif; }
svg .axhead { fill: var(--muted); }
svg .vline { stroke: var(--muted); stroke-width: 1.2; stroke-dasharray: 4 4; }
.vtable { border-collapse: collapse; margin: 4px auto; font-variant-numeric: tabular-nums; }
.vtable th, .vtable td { padding: 4px 10px; border-bottom: 1px solid var(--line); text-align: right; white-space: nowrap; }
.vtable thead th { font-weight: 600; border-bottom: 2px solid var(--line); }
.vtable tbody th { text-align: left; font-weight: 400; }
.vtable td.missing { color: var(--accent); font-size: 0.85rem; }
.vtable tr.diff th, .vtable tr.diff td { color: var(--muted); font-size: 0.9rem; }
.vtable tr.diff td { text-align: center; }
@media (max-width: 560px) { .vtable th, .vtable td { padding: 4px 4px; font-size: 0.85rem; } }

/* their worked examples in the tutor */
.tutor-text .tq { margin: 8px 0; padding-left: 1.4em; font-weight: 600; }
.tutor-text details { margin: 2px 0 12px 2.1em; }
.tutor-text summary { cursor: pointer; color: var(--accent); font-size: 0.93rem; }
.tutor-text .wrong { margin: 6px 0; padding-left: 1.2em; font-size: 0.93rem; }
.tutor-text .wrong li { margin: 8px 0; }
.tag { display: inline-block; margin-left: 4px; padding: 0 8px; border: 1px solid currentColor; border-radius: 999px; color: var(--bad); font-size: 0.78rem; font-weight: 600; }
.short { list-style: none; padding-left: 0; }
.short li { margin: 4px 0; }
/* a graph as an answer (a choice of graphs): small, below its number */
.short svg.cgraph, .tutor-text p > b > svg.cgraph { display: block; width: 100%; max-width: 280px; height: auto; margin-top: 4px; }