/* Explain It Back - an exam paper on a desk: cream ruled paper with a red margin line, a navy ink header, a yellow
 * highlighter on the hot-spot rows, red-pen marks once graded, and a rubber stamp for the verdict. */
:root {
  --bg: #e9edf3; --ink: #1d2740; --muted: #586179; --card: #ffffff; --line: #d3d9e4;
  --paper: #fcf8ec; --rule: #c6d6ee; --margin: #e49a92; --pen: #b92a22; --pen-soft: #fbe3df;
  --hi: #fff09a; --hi-ink: #3d3300; --add: #e5f4e8; --add-ink: #1b5e30; --del: #fbe8e5; --del-ink: #8d2a1f;
  --navy: #26375c; --navy-ink: #ffffff; --chip: #f3f5f9;
  --ok: #1d7a3d; --ok-bg: #e2f3e7; --amber: #9a5b00; --amber-bg: #fdf0d8; --red: #b3261e; --red-bg: #fbe4e1; --slate: #4d5870; --slate-bg: #e8ebf1;
  --serif: Georgia, "Iowan Old Style", "Palatino Linotype", "Book Antiqua", serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
  color-scheme: light;
}
:root[data-theme="dark"] {
  --bg: #0f131b; --ink: #e5e9f1; --muted: #a0a9bb; --card: #171c27; --line: #2d3546;
  --paper: #1b2130; --rule: #2a3a55; --margin: #8a4741; --pen: #ff8f85; --pen-soft: #3a2020;
  --hi: #5c4d08; --hi-ink: #fff3b8; --add: #15301f; --add-ink: #9fe0b2; --del: #3a1d1b; --del-ink: #ffb3a8;
  --navy: #9db6e8; --navy-ink: #0f131b; --chip: #1e2533;
  --ok: #7fdc9d; --ok-bg: #133022; --amber: #ffc56b; --amber-bg: #372912; --red: #ff9b92; --red-bg: #3c1a18; --slate: #b8c2d6; --slate-bg: #252c3b;
  color-scheme: dark;
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 16px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; overflow-x: hidden; }
a { color: var(--navy); }
button, input, textarea, select { font: inherit; color: inherit; }
.hidden { display: none !important; }
.visually-hidden { position: absolute !important; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.small { font-size: 0.87rem; }
.muted { color: var(--muted); }
.mono { font-family: var(--mono); }
.note { background: var(--amber-bg); color: var(--ink); border-left: 4px solid var(--amber); padding: 6px 10px; border-radius: 4px; }

/* Header */
.bar { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; padding: 10px 16px; background: var(--navy); color: var(--navy-ink); }
.bar .back { color: var(--navy-ink); text-decoration: none; font-size: 0.9rem; opacity: 0.9; }
.brand { display: flex; align-items: center; gap: 8px; font-size: 1.05rem; flex: 1 1 auto; min-width: 0; }
.logo { width: 28px; height: 28px; flex: none; }
.lg-paper { fill: #fcf8ec; stroke: #1d2740; stroke-width: 2; }
.lg-rule { stroke: #7fa3d6; stroke-width: 1.6; fill: none; }
.lg-pen { fill: none; stroke: #c8312b; stroke-width: 2.4; stroke-linecap: round; stroke-linejoin: round; }
.session { display: flex; gap: 6px; flex-wrap: wrap; align-items: center; }
.bar .pill { border-color: color-mix(in srgb, var(--navy-ink) 45%, transparent); color: var(--navy-ink); background: transparent; }
.bar .pill.solid { background: var(--navy-ink); color: var(--navy); }

/* Controls */
.pill { display: inline-flex; align-items: center; gap: 4px; border: 1.5px solid var(--line); background: var(--card); color: var(--ink); border-radius: 999px; padding: 5px 13px; cursor: pointer; text-decoration: none; font-size: 0.92rem; line-height: 1.3; }
.pill:hover:not(:disabled) { border-color: var(--navy); }
.pill.solid { background: var(--navy); color: var(--navy-ink); border-color: var(--navy); }
.pill.big { padding: 9px 20px; font-size: 1rem; font-weight: 600; }
.pill.tiny { padding: 2px 10px; font-size: 0.82rem; }
.pill.ghost { cursor: default; }
.pill:disabled { opacity: 0.5; cursor: not-allowed; }
.chip { border: 1.5px dashed var(--line); background: var(--chip); color: var(--ink); border-radius: 6px; padding: 4px 10px; cursor: pointer; font-size: 0.88rem; }
.chip.on { border-style: solid; border-color: var(--pen); background: var(--pen-soft); }
.seg { border: 1.5px solid var(--line); background: var(--card); padding: 4px 14px; cursor: pointer; font-weight: 600; }
.seg:first-of-type { border-radius: 8px 0 0 8px; }
.seg:last-of-type { border-radius: 0 8px 8px 0; }
.seg + .seg { border-left: 0; }
.seg.on { background: var(--navy); color: var(--navy-ink); border-color: var(--navy); }
:focus-visible { outline: 3px solid color-mix(in srgb, var(--pen) 70%, transparent); outline-offset: 2px; }

main { max-width: 1180px; margin: 0 auto; padding: 0 16px 40px; }
.hero { padding: 22px 0 8px; }
.kicker { margin: 0 0 8px; color: var(--muted); font-size: 0.92rem; max-width: 75ch; }
.hero h1 { font-family: var(--serif); font-size: clamp(1.7rem, 4.6vw, 2.7rem); line-height: 1.12; margin: 0 0 10px; overflow-wrap: break-word; text-wrap: balance; }
.lede { margin: 0 0 12px; max-width: 72ch; }
.samples { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; }

.layout { display: grid; grid-template-columns: minmax(0, 1fr); gap: 14px; margin-top: 14px; }
@media (min-width: 980px) { .layout { grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr); } }
.panel { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 14px 16px; margin-top: 14px; min-width: 0; }
.layout .panel { margin-top: 0; }
.ph { display: flex; align-items: center; gap: 8px; font-size: 1.12rem; margin: 0 0 10px; }
.step-no { display: inline-grid; place-items: center; width: 26px; height: 26px; border-radius: 50%; border: 2px solid var(--pen); color: var(--pen); font-size: 0.85rem; font-weight: 700; flex: none; }
.lbl { display: block; font-weight: 600; margin: 10px 0 4px; font-size: 0.93rem; }
textarea, input[type="text"] { width: 100%; border: 1.5px solid var(--line); border-radius: 8px; background: var(--card); padding: 8px 10px; }
#diff { font-family: var(--mono); font-size: 0.82rem; line-height: 1.45; resize: vertical; white-space: pre; overflow-wrap: normal; overflow-x: auto; }
.drop { border: 1.5px dashed var(--line); border-radius: 8px; padding: 6px 10px; margin-top: 6px; }
.drop.over { border-color: var(--pen); background: var(--pen-soft); }
.filelbl { color: var(--navy); text-decoration: underline; cursor: pointer; }
.row2 { display: flex; gap: 14px; flex-wrap: wrap; align-items: flex-end; }
.count { border: 0; padding: 0; margin: 0; }
.count legend { padding: 0; }
.focusbox { flex: 1 1 220px; min-width: 0; }
.stats { margin: 10px 0 4px; color: var(--muted); overflow-wrap: anywhere; }
.flags { list-style: none; padding: 0; margin: 6px 0 0; display: grid; gap: 4px; }
.flags li { font-size: 0.88rem; display: flex; gap: 8px; align-items: baseline; }
.lv { font-size: 0.72rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.04em; padding: 1px 6px; border-radius: 4px; flex: none; }
.lv-fix .lv { background: var(--red-bg); color: var(--red); }
.lv-warn .lv { background: var(--amber-bg); color: var(--amber); }
.lv-info .lv { background: var(--slate-bg); color: var(--slate); }

/* The listing */
.listing { max-height: 620px; overflow: auto; border: 1px solid var(--line); border-radius: 8px; background: var(--paper); font-family: var(--mono); font-size: 0.8rem; }
.empty-list { padding: 18px; font-family: system-ui, sans-serif; color: var(--muted); }
.lfile + .lfile { border-top: 2px solid var(--line); }
.lfile-h { position: sticky; top: 0; z-index: 2; display: flex; gap: 8px; align-items: center; flex-wrap: wrap; padding: 6px 10px; background: var(--card); border-bottom: 1px solid var(--line); }
.lpath { overflow-wrap: anywhere; }
.ladd { color: var(--add-ink); } .ldel { color: var(--del-ink); }
.lhunk { padding: 3px 10px; color: var(--muted); background: color-mix(in srgb, var(--rule) 35%, transparent); }
.lrows { min-width: max-content; }
.lrow { display: grid; grid-template-columns: 3.4em 1.4em auto; align-items: start; position: relative; }
.lrow.add { background: var(--add); }
.lrow.del { background: var(--del); }
.lrow.hot .lcode { background: linear-gradient(transparent 12%, var(--hi) 12%, var(--hi) 88%, transparent 88%); color: var(--hi-ink); }
.lrow.flash { outline: 3px solid var(--pen); outline-offset: -2px; }
.lno { text-align: right; padding-right: 8px; color: var(--muted); user-select: none; border-right: 2px solid var(--margin); }
.lsign { text-align: center; color: var(--muted); user-select: none; }
.lrow.add .lsign { color: var(--add-ink); } .lrow.del .lsign { color: var(--del-ink); }
.lcode { white-space: pre; padding-right: 10px; font-family: inherit; }
.ltags { grid-column: 3; display: flex; gap: 4px; flex-wrap: wrap; padding: 0 0 3px 0; font-family: system-ui, sans-serif; }
.spot { font-size: 0.72rem; background: var(--hi); color: var(--hi-ink); border: 1px solid color-mix(in srgb, var(--hi-ink) 30%, transparent); border-radius: 3px; padding: 0 5px; }
.qpin { font: 700 0.72rem system-ui, sans-serif; border: 1.5px solid var(--pen); color: var(--pen); background: var(--card); border-radius: 10px 10px 10px 2px; padding: 0 6px; cursor: pointer; }
.qpin.on { background: var(--pen); color: var(--card); }

.askbox .runrow, .handin .runrow { display: flex; gap: 12px; align-items: center; flex-wrap: wrap; margin-top: 8px; }
.gate { margin: 8px 0 0; padding: 8px 10px; border-radius: 8px; background: var(--slate-bg); }
.gate .pill { margin-left: 4px; }
.progress .steps { list-style: none; padding: 0; margin: 6px 0; display: grid; gap: 3px; }
.step { color: var(--muted); }
.step.active { color: var(--ink); font-weight: 600; }
.step.done { color: var(--ok); }
.step-ic { display: inline-block; width: 1.2em; font-family: var(--mono); }
.raw { white-space: pre-wrap; overflow-wrap: anywhere; font-family: var(--mono); font-size: 0.8rem; max-height: 400px; overflow: auto; }

/* The exam paper */
.exam { margin-top: 18px; }
.sheetwrap { display: grid; grid-template-columns: minmax(0, 1fr); gap: 14px; align-items: start; }
@media (min-width: 900px) { .sheetwrap { grid-template-columns: minmax(0, 1fr) 190px; } .sheet { position: sticky; top: 12px; } }
.paper { position: relative; background: var(--paper); border: 1px solid var(--line); border-radius: 4px; padding: 22px 18px 18px 56px; box-shadow: 0 2px 0 var(--line), 0 10px 24px -14px rgba(20, 30, 60, 0.35);
  background-image: linear-gradient(90deg, transparent 42px, var(--margin) 42px, var(--margin) 44px, transparent 44px); font-family: var(--serif); min-width: 0; }
.phead { position: relative; padding-right: 0; }
.pline { margin: 0; color: var(--muted); letter-spacing: 0.08em; font-family: var(--mono); padding-right: 66px; }
.phead h2 { font-size: clamp(1.3rem, 3.4vw, 1.75rem); line-height: 1.2; margin: 4px 0 6px; overflow-wrap: break-word; padding-right: 64px; }
.esum { margin: 0 0 10px; }
.score { position: absolute; top: -6px; right: 0; width: 60px; height: 60px; border: 3px solid var(--pen); border-radius: 50%; display: grid; place-items: center; color: var(--pen); font: 700 1.05rem var(--serif); transform: rotate(-8deg); background: color-mix(in srgb, var(--paper) 80%, transparent); }
.stamp { display: inline-block; margin: 2px 0 12px; padding: 4px 14px; border: 3px double currentColor; border-radius: 6px; font: 800 1.05rem system-ui, sans-serif; text-transform: uppercase; letter-spacing: 0.1em; transform: rotate(-3deg); }
.stamp.s-ship { color: var(--ok); background: var(--ok-bg); }
.stamp.s-reread { color: var(--amber); background: var(--amber-bg); }
.stamp.s-hold { color: var(--red); background: var(--red-bg); }
.stamp.s-needs-answers, .stamp.s-needs-diff { color: var(--slate); background: var(--slate-bg); }
.walk { border: 1.5px dashed var(--rule); border-radius: 6px; padding: 8px 12px; margin: 6px 0 14px; background: color-mix(in srgb, var(--card) 40%, transparent); }
.walk h3, .testsbox h3, .tipsbox h3 { font-size: 1rem; margin: 0 0 4px; font-family: system-ui, sans-serif; }
.walklist { margin: 0; padding-left: 18px; }
.walklist li { margin: 4px 0; overflow-wrap: anywhere; }
.walklist .mono { font-size: 0.85rem; }
.look { color: var(--muted); font-style: italic; }
.qs { list-style: none; margin: 0; padding: 0; }
.q { position: relative; display: block; padding: 10px 0 14px; border-top: 1px solid var(--rule); }
.qmargin { position: absolute; left: -50px; top: 10px; width: 40px; text-align: center; }
.qno { display: block; font: 700 1.15rem var(--serif); }
.pen { display: block; font: 700 1.7rem/1 var(--serif); color: var(--pen); margin-top: 2px; }
.q.m-solid .pen { color: var(--ok); }
.qtop { display: flex; gap: 6px; flex-wrap: wrap; align-items: center; margin: 0 0 4px; font-family: system-ui, sans-serif; }
.qkind { font-size: 0.74rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em; padding: 1px 7px; border-radius: 3px; background: var(--slate-bg); color: var(--slate); }
.qloc { font: 0.78rem var(--mono); background: none; border: 0; border-bottom: 1.5px dotted var(--navy); color: var(--navy); cursor: pointer; padding: 0; overflow-wrap: anywhere; text-align: left; }
.qspot { font-size: 0.72rem; background: var(--hi); color: var(--hi-ink); padding: 0 5px; border-radius: 3px; }
.qask { margin: 0 0 6px; font-size: 1.03rem; }
textarea.ruled { font-family: var(--serif); font-size: 1rem; line-height: 28px; padding: 2px 8px; border: 0; border-bottom: 1.5px solid var(--rule); border-radius: 0; resize: vertical; min-height: 88px;
  background: transparent; background-image: repeating-linear-gradient(transparent, transparent 27px, var(--rule) 27px, var(--rule) 28px); background-attachment: local; }
textarea.ruled:focus { background-color: color-mix(in srgb, var(--card) 50%, transparent); }
.bubbles { display: flex; gap: 8px; margin-top: 6px; font-family: system-ui, sans-serif; }
.bubble { display: inline-flex; align-items: center; gap: 6px; background: none; border: 0; cursor: pointer; font-size: 0.85rem; color: var(--muted); padding: 2px 4px; }
.bubble::before { content: ""; width: 14px; height: 14px; border-radius: 50%; border: 1.5px solid var(--muted); }
.bubble.on { color: var(--ink); font-weight: 600; }
.bubble.on::before { background: var(--ink); border-color: var(--ink); }
.redpen { margin-top: 8px; padding: 6px 10px; border-left: 3px solid var(--pen); background: var(--pen-soft); color: var(--ink); border-radius: 0 6px 6px 0; }
.redpen p { margin: 2px 0; }
.rp-mark { color: var(--pen); font-style: italic; }
.q.m-solid .redpen { border-left-color: var(--ok); background: var(--ok-bg); }
.q.m-solid .rp-mark { color: var(--ok); }
.rp-key { font-family: system-ui, sans-serif; font-size: 0.9rem; }
.q.stale .redpen { opacity: 0.6; }
.testsbox, .tipsbox { margin-top: 12px; padding-top: 10px; border-top: 1px solid var(--rule); }
.handin { margin-top: 14px; padding-top: 10px; border-top: 2px solid var(--rule); font-family: system-ui, sans-serif; }

/* The bubble sheet */
.sheet { background: var(--card); border: 1px solid var(--line); border-radius: 6px; padding: 10px; border-top: 6px solid var(--pen); }
.sheet-t { width: 100%; border-collapse: collapse; font-size: 0.85rem; }
.sheet-t th { font-weight: 700; color: var(--muted); padding: 3px 2px; }
.sheet-t td { text-align: center; padding: 3px 2px; }
.sheet-t tbody tr.answered th { color: var(--ink); }
.bdot { display: inline-block; width: 15px; height: 15px; border-radius: 50%; border: 1.5px solid var(--muted); vertical-align: middle; }
.bdot.fill { border-color: transparent; }
.bdot.f-solid { background: var(--ok); } .bdot.f-shaky { background: var(--amber); } .bdot.f-wrong { background: var(--red); } .bdot.f-blank { background: var(--slate); }
.bdot.ghost { border-style: dashed; }
.sheet-foot { margin: 8px 0 0; font-weight: 600; font-size: 0.9rem; text-align: center; }

.recon { list-style: none; padding: 0; margin: 8px 0; display: grid; gap: 4px; }
.recon li { font-size: 0.88rem; padding: 4px 8px; border-radius: 6px; background: var(--slate-bg); overflow-wrap: anywhere; }
.recon li.warn { background: var(--amber-bg); }
.recon li.none { background: var(--ok-bg); }
.graded .ghead { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.graded h3 { margin: 12px 0 4px; font-size: 1rem; }
.ghead h3 { margin: 0; font-family: var(--serif); font-size: 1.25rem; overflow-wrap: break-word; min-width: 0; }
.verdict { display: inline-block; font-weight: 800; text-transform: uppercase; font-size: 0.82rem; letter-spacing: 0.06em; padding: 3px 10px; border-radius: 4px; border: 2px solid currentColor; }
.v-ship { color: var(--ok); background: var(--ok-bg); } .v-reread { color: var(--amber); background: var(--amber-bg); } .v-hold { color: var(--red); background: var(--red-bg); }
.v-needs-answers, .v-none { color: var(--slate); background: var(--slate-bg); }
.summary { font-size: 1.02rem; }
.plain { margin: 4px 0; padding-left: 20px; }
.plain li { margin: 3px 0; }
.exports, .cardrow { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 12px; }
.hist { list-style: none; padding: 0; margin: 10px 0 0; display: grid; gap: 6px; }
.hrow { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; border: 1px solid var(--line); border-radius: 8px; padding: 6px 10px; }
.hinfo { flex: 1 1 200px; display: flex; flex-direction: column; min-width: 0; overflow-wrap: anywhere; }
.none { color: var(--muted); font-style: italic; }
.foot { max-width: 1180px; margin: 0 auto; padding: 18px 16px 40px; color: var(--muted); font-size: 0.88rem; border-top: 1px solid var(--line); }
.toasts { position: fixed; bottom: 14px; left: 50%; transform: translateX(-50%); display: grid; gap: 6px; z-index: 50; width: min(92vw, 520px); }
.toast { background: var(--navy); color: var(--navy-ink); padding: 9px 14px; border-radius: 8px; box-shadow: 0 6px 20px rgba(0, 0, 0, 0.25); transition: opacity 0.5s; font-size: 0.92rem; }
.toast.err { background: var(--red); color: #fff; }
:root[data-theme="dark"] .toast.err { color: #1a0d0c; }
.toast a { color: inherit; font-weight: 700; }
.toast.gone { opacity: 0; }

@media (max-width: 600px) {
  .paper { padding: 16px 12px 14px 44px; background-image: linear-gradient(90deg, transparent 32px, var(--margin) 32px, var(--margin) 34px, transparent 34px); }
  .qmargin { left: -42px; width: 32px; }
  .bar { padding: 8px 12px; }
  .listing { max-height: 460px; }
}
@media print {
  .bar, .hero, .layout, .askbox, .histbox, .exports, .handin, .foot, .toasts, #progressPanel { display: none !important; }
  body { background: #fff; }
  .paper { box-shadow: none; }
}