/* SPDX-License-Identifier: GPL-3.0-or-later
   Copyright (c) 2026 Jyotiprakash Mishra. Based on "xv6, line by line" by Jyotiprakash Mishra
   (https://xv6.jyotiprakash.org); see NOTICE for the attribution term (GPLv3 section 7(b)). */
/* xv6, line by line: site styles. Colors are tokens; dark mode redefines them. */

:root {
  --bg: #fbfaf7;
  --bg-2: #f3f1ec;
  --bg-3: #e9e6df;
  --fg: #1f2328;
  --fg-2: #57606a;
  --fg-3: #8a929a;
  --line: #dedad2;
  --accent: #2456b8;
  --accent-bg: #e3ebfa;
  --hl: #ffe8a3;
  --target: #fff4cc;
  --tip-bg: #ffffff;
  --shadow: 0 6px 24px rgba(30, 30, 30, .14);

  --kw: #9a2f8f;
  --kt: #1f6f8b;
  --st: #0f7a3d;
  --nu: #b3541e;
  --cm: #737b84;
  --pp: #8a5a00;
  --op: #5b636b;
  --insn: #9a2f8f;
  --reg: #1f6f8b;
  --csr: #b02a37;
  --dir: #8a5a00;
  --lbl: #2456b8;
  --sec: #6b4fbb;
  --var: #1f6f8b;
  --flag: #6b4fbb;
  --tgt: #2456b8;

  --mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #15171a; --bg-2: #1c1f23; --bg-3: #262a30; --fg: #e3e6ea; --fg-2: #a6adb6;
    --fg-3: #737b85; --line: #2e333a; --accent: #7aa7ff; --accent-bg: #1f2c47;
    --hl: #5a4a12; --target: #2f2a14; --tip-bg: #22262b; --shadow: 0 6px 24px rgba(0,0,0,.5);
    --kw: #d39bf0; --kt: #6fc3df; --st: #8fd19e; --nu: #f0a86c; --cm: #7f8893; --pp: #e3b75f;
    --op: #9aa3ad; --insn: #d39bf0; --reg: #6fc3df; --csr: #ff8b94; --dir: #e3b75f;
    --lbl: #7aa7ff; --sec: #b9a3f5; --var: #6fc3df; --flag: #b9a3f5; --tgt: #7aa7ff;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #15171a; --bg-2: #1c1f23; --bg-3: #262a30; --fg: #e3e6ea; --fg-2: #a6adb6;
  --fg-3: #737b85; --line: #2e333a; --accent: #7aa7ff; --accent-bg: #1f2c47;
  --hl: #5a4a12; --target: #2f2a14; --tip-bg: #22262b; --shadow: 0 6px 24px rgba(0,0,0,.5);
  --kw: #d39bf0; --kt: #6fc3df; --st: #8fd19e; --nu: #f0a86c; --cm: #7f8893; --pp: #e3b75f;
  --op: #9aa3ad; --insn: #d39bf0; --reg: #6fc3df; --csr: #ff8b94; --dir: #e3b75f;
  --lbl: #7aa7ff; --sec: #b9a3f5; --var: #6fc3df; --flag: #b9a3f5; --tgt: #7aa7ff;
  color-scheme: dark;
}

* { box-sizing: border-box; }
html, body { margin: 0; height: 100%; }
body { background: var(--bg); color: var(--fg); font: 15px/1.5 var(--sans); }
a { color: var(--accent); }
kbd { font: 12px var(--mono); border: 1px solid var(--line); border-bottom-width: 2px;
      border-radius: 4px; padding: 0 5px; background: var(--bg-2); }
code { font-family: var(--mono); font-size: .92em; }

/* ---------------------------------------------------------------- header */
.top { position: sticky; top: 0; z-index: 20; height: 52px; display: flex; align-items: center;
       gap: 12px; padding: 0 16px; background: var(--bg-2); border-bottom: 1px solid var(--line); }
.brand { font-weight: 700; color: var(--fg); text-decoration: none; white-space: nowrap; }
.brand span { font-weight: 400; color: var(--fg-2); }
.crumb { font: 13px var(--mono); color: var(--fg-2); overflow: hidden; text-overflow: ellipsis;
         white-space: nowrap; flex: 1; min-width: 0; }
.search { position: relative; width: min(380px, 40vw); }
.search input { width: 100%; height: 34px; padding: 0 10px; border-radius: 8px;
                border: 1px solid var(--line); background: var(--bg); color: var(--fg); font: inherit;
                font-size: 14px; }
.search input:focus { outline: 2px solid var(--accent); outline-offset: -1px; }
#results { position: absolute; right: 0; top: 40px; width: min(520px, 92vw); max-height: 70vh;
           overflow: auto; background: var(--tip-bg); border: 1px solid var(--line);
           border-radius: 10px; box-shadow: var(--shadow); padding: 4px; }
#results a { display: flex; gap: 8px; align-items: baseline; padding: 6px 8px; border-radius: 6px;
             color: var(--fg); text-decoration: none; }
#results a.sel, #results a:hover { background: var(--accent-bg); }
#results .r-name { font-family: var(--mono); font-size: 13.5px; }
#results .r-where { color: var(--fg-3); font-size: 12px; margin-left: auto; white-space: nowrap; }
#results .none { padding: 8px; color: var(--fg-3); }
.icon-btn { border: 1px solid transparent; background: none; color: var(--fg-2); font-size: 18px;
            width: 34px; height: 34px; border-radius: 8px; cursor: pointer; flex: none; }
.icon-btn:hover { background: var(--bg-3); color: var(--fg); }
#tree-toggle { display: none; }

/* ---------------------------------------------------------------- layout */
.layout { display: grid; grid-template-columns: 250px minmax(0, 1fr) 400px;
          height: calc(100vh - 52px); }
.layout.home { grid-template-columns: 250px minmax(0, 1fr); }
.tree, .main, .panel { overflow: auto; min-height: 0; }
.tree { border-right: 1px solid var(--line); padding: 8px 0 24px; font-size: 13.5px;
        background: var(--bg-2); }
.tree summary { cursor: pointer; padding: 4px 14px; color: var(--fg-2); font-weight: 600;
                font-family: var(--mono); font-size: 12.5px; }
.tree ul { list-style: none; margin: 0 0 6px; padding: 0; }
.tree li a { display: block; padding: 2px 14px 2px 28px; color: var(--fg); text-decoration: none;
             font-family: var(--mono); font-size: 13px; border-left: 3px solid transparent; }
.tree li { display: flex; align-items: center; }
.tree li a { flex: 1; }
.tree li a:hover { background: var(--bg-3); }
.tree li a.here { background: var(--accent-bg); border-left-color: var(--accent); font-weight: 600; }
.tree li.minor a { color: var(--fg-3); }
.badge { font: 10px var(--sans); text-transform: uppercase; letter-spacing: .04em; color: var(--fg-2);
         border: 1px solid var(--line); border-radius: 4px; padding: 0 4px; margin-right: 10px; }

/* ---------------------------------------------------------------- file head */
.file-head { padding: 18px 24px 10px; border-bottom: 1px solid var(--line); }
.file-head h1 { margin: 0; font: 600 20px var(--mono); }
.meta { margin: 4px 0 0; color: var(--fg-2); font-size: 13px; }
.gen-note { margin: 8px 0 0; font-size: 13.5px; background: var(--bg-2); padding: 8px 10px;
            border-radius: 6px; border: 1px solid var(--line); }
.incby { margin-top: 6px; font-size: 13px; color: var(--fg-2); }
.incby summary { cursor: pointer; }
.incby a { font-family: var(--mono); font-size: 12.5px; }

/* ---------------------------------------------------------------- code */
.code { font: 13.5px/1.6 var(--mono); padding: 8px 0 40vh; tab-size: 8; -moz-tab-size: 8; }
.l { display: flex; white-space: pre; min-height: 1.6em; scroll-margin-top: 30vh; }
.l .n { flex: none; width: 4.2em; padding-right: 1.1em; text-align: right; color: var(--fg-3);
        text-decoration: none; user-select: none; -webkit-user-select: none; }
.l .n:hover { color: var(--accent); }
.l .t { flex: 1; padding-right: 24px; }
.l.target { background: var(--target); }
.l.target .n { color: var(--fg); font-weight: 600; }
.l.flash { animation: flash 1.2s ease-out; }
@keyframes flash { from { background: var(--hl); } to { background: var(--target); } }

.kw { color: var(--kw); } .kt { color: var(--kt); } .st { color: var(--st); }
.nu { color: var(--nu); } .cm { color: var(--cm); font-style: italic; } .pp { color: var(--pp); }
.op { color: var(--op); } .nb { color: var(--kt); }
.insn { color: var(--insn); } .reg { color: var(--reg); } .csr { color: var(--csr); font-weight: 600; }
.dir { color: var(--dir); } .lbl { color: var(--lbl); font-weight: 600; } .sec { color: var(--sec); }
.var { color: var(--var); } .flag { color: var(--flag); } .tgt { color: var(--tgt); font-weight: 600; }
.av { color: var(--csr); } .fn { color: var(--kw); }
[data-g] { cursor: help; }

a.sy { color: inherit; text-decoration: none; border-radius: 3px; }
a.sy:hover { text-decoration: underline; text-decoration-color: var(--accent);
             text-underline-offset: 3px; }
a.sy.def { font-weight: 700; }
a.sy.hl { background: var(--hl); box-shadow: 0 0 0 1px var(--hl); }
a.fl { color: inherit; text-decoration: underline dotted var(--fg-3); text-underline-offset: 3px; }
a.fl:hover { text-decoration-color: var(--accent); color: var(--accent); }

/* ---------------------------------------------------------------- panel */
.panel { border-left: 1px solid var(--line); background: var(--bg); display: flex;
         flex-direction: column; }
.panel-tabs { display: flex; gap: 4px; padding: 8px 10px 0; border-bottom: 1px solid var(--line);
              position: sticky; top: 0; background: var(--bg); z-index: 1; }
.panel-tabs [role=tab] { border: none; background: none; color: var(--fg-2); font: 600 13px var(--sans);
                         padding: 8px 10px; border-bottom: 2px solid transparent; cursor: pointer; }
.panel-tabs [aria-selected=true] { color: var(--fg); border-bottom-color: var(--accent); }
.panel-close { margin-left: auto; display: none; }
.panel-body { padding: 14px 16px 40px; font-size: 14px; }
.panel .empty { color: var(--fg-2); }
.sym-head { margin: 0 0 2px; font: 600 17px var(--mono); word-break: break-all; }
.kind { display: inline-block; font: 600 10.5px var(--sans); text-transform: uppercase;
        letter-spacing: .05em; color: var(--accent); background: var(--accent-bg);
        border-radius: 4px; padding: 1px 6px; margin-right: 6px; vertical-align: 2px; }
.sym-type { font: 13px var(--mono); color: var(--fg-2); margin: 4px 0; word-break: break-word; }
.sym-def { margin: 8px 0 14px; font-size: 13.5px; color: var(--fg-2); }
.sym-def a { font-family: var(--mono); font-size: 13px; }
.occ-file { margin: 14px 0 4px; font: 600 12.5px var(--mono); color: var(--fg-2);
            display: flex; justify-content: space-between; }
.occ { display: flex; gap: 8px; padding: 3px 6px; border-radius: 5px; text-decoration: none;
       color: var(--fg); font: 12.5px/1.5 var(--mono); }
.occ:hover { background: var(--bg-2); }
.occ.cur { background: var(--accent-bg); }
.occ .ol { color: var(--fg-3); flex: none; min-width: 3.2em; text-align: right; }
.occ .os { white-space: pre; overflow: hidden; text-overflow: ellipsis; }
.occ .os b { background: var(--hl); font-weight: 600; border-radius: 2px; }
.occ .role { flex: none; margin-left: auto; font: 600 10px var(--sans); text-transform: uppercase;
             color: var(--fg-3); padding-top: 2px; }
.sum { color: var(--fg-2); font-size: 13px; }
.pick a { display: block; font-family: var(--mono); font-size: 13px; padding: 3px 0; }

/* ---------------------------------------------------------------- tooltip */
.tip { position: fixed; z-index: 50; max-width: min(480px, 92vw); max-height: 60vh; overflow: auto;
       background: var(--tip-bg); color: var(--fg); border: 1px solid var(--line); border-radius: 10px;
       box-shadow: var(--shadow); padding: 10px 12px; font-size: 13.5px; }
.tip a.gl, .tip a.sy, .tip a.fl { color: var(--accent); }
.tip .tn { font: 600 14px var(--mono); }
.tip .tt { font: 12.5px var(--mono); color: var(--fg-2); margin-top: 2px; word-break: break-word; }
.tip .tw { color: var(--fg-2); font-size: 12.5px; margin-top: 6px; }
.tip pre { margin: 6px 0 0; font: 12px/1.5 var(--mono); background: var(--bg-2); padding: 6px 8px;
           border-radius: 6px; white-space: pre-wrap; word-break: break-word; }
.tip .hint { color: var(--fg-3); font-size: 12px; margin-top: 6px; }

/* ---------------------------------------------------------------- home */
.prose { padding: 28px clamp(16px, 4vw, 48px) 60px; max-width: 980px; }
.prose h1 { font-size: 30px; margin: 0 0 8px; }
.prose h2 { font-size: 19px; margin: 32px 0 10px; }
.lede { font-size: 17px; color: var(--fg-2); max-width: 70ch; }
.howto li, .order li { margin: 5px 0; }
.files { border-collapse: collapse; width: 100%; font-size: 14px; }
.files th, .files td { text-align: left; padding: 5px 10px; border-bottom: 1px solid var(--line); }
.files th { color: var(--fg-2); font-weight: 600; font-size: 12.5px; }
.files td a { font-family: var(--mono); font-size: 13.5px; }
.files .num { text-align: right; font-variant-numeric: tabular-nums; }
.foot { margin-top: 36px; color: var(--fg-3); font-size: 13px; }

/* ---------------------------------------------------------------- responsive */
@media (max-width: 1180px) {
  .layout { grid-template-columns: 230px minmax(0, 1fr); }
  .panel { position: fixed; right: 0; top: 52px; bottom: 0; width: min(420px, 100vw); z-index: 30;
           box-shadow: var(--shadow); transform: translateX(105%); transition: transform .18s; }
  body.panel-open .panel { transform: none; }
  .panel-close { display: block; }
}
@media (max-width: 760px) {
  .layout, .layout.home { grid-template-columns: minmax(0, 1fr); }
  #tree-toggle { display: block; }
  .tree { position: fixed; left: 0; top: 52px; bottom: 0; width: min(300px, 86vw); z-index: 30;
          box-shadow: var(--shadow); transform: translateX(-105%); transition: transform .18s; }
  body.tree-open .tree { transform: none; }
  .crumb { display: none; }
  .search { flex: 1; width: auto; }
  .brand span { display: none; }
  .file-head { padding: 14px 16px 10px; }
  .code { font-size: 12.5px; }
  .l .n { width: 3.4em; padding-right: .8em; }
}

/* ---------------------------------------------------------------- notes */
.toplink { color: var(--fg-2); font-size: 13.5px; text-decoration: none; white-space: nowrap; }
.toplink:hover { color: var(--accent); }
.dot { width: 7px; height: 7px; border-radius: 50%; background: var(--accent); margin-right: 12px;
       flex: none; }
.btn { font: 600 13px var(--sans); color: var(--fg); background: var(--bg-2); border: 1px solid var(--line);
       border-radius: 7px; padding: 5px 11px; cursor: pointer; }
.btn:hover:not([disabled]) { border-color: var(--accent); color: var(--accent); }
.btn[disabled] { opacity: .4; cursor: default; }
.about { margin-top: 12px; font-size: 14.5px; max-width: 80ch; }
.about > summary { cursor: pointer; font-weight: 600; font-size: 13px; color: var(--fg-2); }
.about p { margin: .6em 0; }
.note-bar { display: flex; gap: 16px; align-items: center; margin-top: 12px; flex-wrap: wrap; }
.inline-toggle { font-size: 13.5px; color: var(--fg-2); display: flex; gap: 6px; align-items: center; cursor: pointer; }

/* gutter: a bar for lines covered by a block note, a dot for line notes */
.l.ib .n { box-shadow: inset -2px 0 0 var(--line); }
.l.bs .n { box-shadow: inset -2px 0 0 var(--fg-3); }
.l.hn .n { position: relative; }
.l.hn .n::after { content: ""; position: absolute; right: 5px; top: .62em; width: 5px; height: 5px;
                  border-radius: 50%; background: var(--accent); }
.code .l { cursor: pointer; }
.code .l.rng { background: var(--bg-2); }
.code .l.rng.target { background: var(--target); }

.note-nav { display: flex; align-items: center; justify-content: space-between; gap: 8px;
            margin-bottom: 10px; font: 600 13px var(--sans); color: var(--fg-2); }
.note { border: 1px solid var(--line); border-radius: 10px; padding: 10px 14px; margin: 0 0 12px;
        background: var(--bg); font-size: 14.5px; line-height: 1.6; }
.note.block { background: var(--bg-2); }
.note h3 { margin: 2px 0 6px; font-size: 15px; }
.note .nl { font: 600 11px var(--sans); text-transform: uppercase; letter-spacing: .05em; }
.note .nl a { color: var(--fg-3); text-decoration: none; }
.note .nl a:hover { color: var(--accent); }
.note p, .about p, .gloss p { margin: .55em 0; }
.note ul, .note ol { padding-left: 1.3em; margin: .4em 0; }
.note li { margin: .2em 0; }
.note code, .about code, .gloss code { background: var(--bg-3); padding: .05em .3em; border-radius: 4px; font-size: .88em; }
.note pre, .gloss pre { background: var(--bg-3); padding: 8px 10px; border-radius: 6px; overflow: auto; font: 12.5px/1.5 var(--mono); }
.note pre code, .gloss pre code { background: none; padding: 0; }
.note table, .gloss table { border-collapse: collapse; font-size: 13px; margin: .5em 0; }
.note th, .note td, .gloss th, .gloss td { border: 1px solid var(--line); padding: 3px 7px; text-align: left; }
a.gl { color: inherit; text-decoration: underline dotted var(--accent); text-underline-offset: 3px; }
a.gl:hover { color: var(--accent); }
.note a.sy, .about a.sy, .gloss a.sy { color: var(--accent); }
.note a.sy code, .about a.sy code { color: var(--accent); }
a.ln-ref { color: var(--accent); }
.tip .gs { margin-top: 6px; line-height: 1.5; }
.tip .gs code { background: var(--bg-3); padding: 0 .25em; border-radius: 3px; font-size: .9em; }

/* inline mode: notes sit between code lines, in prose font */
.inline-note { white-space: normal; font-family: var(--sans); margin: 6px 24px 8px 4.2em; max-width: 80ch; cursor: auto; }
.inline-note.line { margin-left: 5.4em; border-left: 3px solid var(--accent); border-radius: 0 10px 10px 0; }

/* glossary page */
.glossary h2 { border-bottom: 1px solid var(--line); padding-bottom: 4px; }
.gloss { padding: 8px 0 14px; scroll-margin-top: 20px; }
.gloss h3 { margin: 0; font: 600 16px var(--mono); }
.gloss:target { background: var(--target); border-radius: 8px; padding-left: 10px; }
.gshort { font-weight: 500; }

/* ================================================================ guided tours */
:root { --m-M: #b02a37; --m-S: #2456b8; --m-U: #0f7a3d; --lockc: #8a5a00; --lockbg: #fff3d6;
        --fxbg: #fff6d8; --fxbar: #e0a100; --others: #6b4fbb; --othersbg: #f4f0fc; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) {
  --m-M: #ff8b94; --m-S: #7aa7ff; --m-U: #8fd19e; --lockc: #e3b75f; --lockbg: #3a2e12;
  --fxbg: #2f2a14; --fxbar: #e3b75f; --others: #b9a3f5; --othersbg: #241f33; } }
:root[data-theme="dark"] { --m-M: #ff8b94; --m-S: #7aa7ff; --m-U: #8fd19e; --lockc: #e3b75f;
  --lockbg: #3a2e12; --fxbg: #2f2a14; --fxbar: #e3b75f; --others: #b9a3f5; --othersbg: #241f33; }

body.tour-page, body.tours-index, body.test-page { height: auto; min-height: 100%; }
.tour { max-width: 1600px; margin: 0 auto; padding: 0 20px 40px; }
.tour-top { position: sticky; top: 52px; z-index: 15; background: var(--bg); display: flex;
            align-items: center; gap: 14px; padding: 10px 0; border-bottom: 1px solid var(--line); }
.tback { color: var(--fg-2); text-decoration: none; font-size: 13.5px; white-space: nowrap; }
.tback::before { content: "← "; }
.ttitle { font-size: 14px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; max-width: 32ch; }
.ttitle b { display: inline-block; min-width: 1.8em; text-align: center; background: var(--accent);
            color: #fff; border-radius: 6px; margin-right: 6px; font-size: 12.5px; padding: 1px 0; }
.segs { flex: 1; display: flex; gap: 3px; min-width: 80px; }
.seg { flex: 1; height: 8px; border: none; border-radius: 4px; background: var(--bg-3); cursor: pointer; padding: 0; }
.seg.past { background: color-mix(in srgb, var(--accent) 55%, var(--bg-3)); }
.seg.now { background: var(--accent); transform: scaleY(1.5); }
.seg:hover { outline: 2px solid var(--accent); outline-offset: 1px; }
.tnav { display: flex; align-items: center; gap: 6px; }
.tnav .count { font: 600 13px var(--sans); color: var(--fg-2); min-width: 7.5em; text-align: center; }
.keys { color: var(--fg-3); font-size: 12px; text-align: center; margin-top: 18px; }

.tstep.enter-fwd { animation: tin-f .28s ease-out; }
.tstep.enter-back { animation: tin-b .28s ease-out; }
@keyframes tin-f { from { opacity: 0; transform: translateX(24px); } to { opacity: 1; transform: none; } }
@keyframes tin-b { from { opacity: 0; transform: translateX(-24px); } to { opacity: 1; transform: none; } }
@media (prefers-reduced-motion: reduce) { .tstep.enter-fwd, .tstep.enter-back { animation: none; } }

/* intro and wrap-up */
.intro-inner { max-width: 860px; margin: 0 auto; padding: 34px 0 10px; }
.tkicker { color: var(--fg-2); font: 600 12.5px var(--sans); text-transform: uppercase; letter-spacing: .06em; margin: 0; }
.intro-inner h1 { font-size: clamp(26px, 4vw, 38px); margin: 6px 0 14px; line-height: 1.15; }
.tsum { font-size: 17px; line-height: 1.65; }
.tsum p { margin: .7em 0; }
.prereq { color: var(--fg-2); }
.cast { background: var(--bg-2); border: 1px solid var(--line); border-radius: 12px; padding: 4px 18px; margin: 18px 0; }
.cast h3 { font-size: 14px; margin: 12px 0 0; color: var(--fg-2); }
.multihart { border-left: 4px solid var(--others); background: var(--othersbg); padding: 12px 16px;
             border-radius: 0 12px 12px 0; margin: 20px 0; font-size: 15px; line-height: 1.55; }
.hp-demo { font: 600 12px var(--sans); color: var(--lockc); background: var(--lockbg); border-radius: 5px; padding: 1px 6px; }
.btn.big { font-size: 15px; padding: 10px 18px; border-radius: 10px; margin: 6px 6px 6px 0; }
.btn.big:not(.resume) { background: var(--accent); color: #fff; border-color: var(--accent); }
.btn.big:not(.resume):hover { filter: brightness(1.08); color: #fff; }
.outline { margin-top: 24px; }
.outline summary { cursor: pointer; font-weight: 600; color: var(--fg-2); }
.outline ol { list-style: none; padding: 0; margin: 10px 0; columns: 2 320px; column-gap: 28px; }
.outline li { break-inside: avoid; padding: 4px 0; font-size: 14.5px; }
.outline a { color: var(--fg); text-decoration: none; }
.outline a:hover { color: var(--accent); }
.outline .on { display: inline-block; width: 1.9em; color: var(--fg-3); font-variant-numeric: tabular-nums; }
.outline .ofile { color: var(--fg-3); font: 12px var(--mono); }
.locktab { border-collapse: collapse; width: 100%; font-size: 14px; margin: 8px 0 20px; }
.locktab th, .locktab td { border-bottom: 1px solid var(--line); padding: 7px 10px; text-align: left; vertical-align: top; }
.locktab th { color: var(--fg-2); font-size: 12.5px; }
.locktab code { color: var(--lockc); background: var(--lockbg); border-radius: 4px; padding: 1px 5px; }
.quiz { display: grid; gap: 10px; margin-bottom: 24px; }
.q { border: 1px solid var(--line); border-radius: 12px; background: var(--bg-2); }
.q > summary { cursor: pointer; padding: 12px 16px; display: flex; gap: 12px; align-items: baseline; list-style: none; }
.q > summary::-webkit-details-marker { display: none; }
.q > summary p { margin: 0; }
.q .qn { flex: none; font: 700 13px var(--sans); color: var(--accent); }
.q > summary::after { content: "Show answer"; margin-left: auto; flex: none; font: 600 12px var(--sans); color: var(--fg-3); }
.q[open] > summary::after { content: "Hide"; }
.qa { padding: 2px 16px 12px 44px; border-top: 1px dashed var(--line); line-height: 1.6; }
.outro-nav { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin-top: 10px; }

/* machine-state display */
.hud { display: flex; flex-wrap: wrap; gap: 8px; padding: 14px 0 6px; }
.hp { display: inline-flex; align-items: center; border: 1px solid var(--line); border-radius: 999px;
      background: var(--bg-2); font-size: 13px; overflow: hidden; }
.hk { font: 600 10.5px var(--sans); text-transform: uppercase; letter-spacing: .05em; color: var(--fg-3);
      padding: 4px 4px 4px 10px; }
.hv { padding: 4px 10px 4px 4px; font-weight: 600; display: inline-flex; gap: 5px; flex-wrap: wrap; align-items: center; }
.h-hart .hv::before { content: ""; width: 8px; height: 8px; border-radius: 50%; background: var(--accent);
                      box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 25%, transparent); margin-right: 3px; }
.h-mode .hv { color: #fff; border-radius: 999px; padding: 2px 10px; margin: 2px 3px 2px 0; }
.m-M .hv { background: var(--m-M); } .m-S .hv { background: var(--m-S); } .m-U .hv { background: var(--m-U); }
.h-intr.on .hv { color: var(--m-U); } .h-intr.off .hv { color: var(--m-M); }
.h-locks { border-color: color-mix(in srgb, var(--lockc) 45%, var(--line)); }
.lk { color: var(--lockc); background: var(--lockbg); border-radius: 5px; padding: 1px 6px; font: 600 12px var(--mono); }
.nolk { color: var(--fg-3); font-weight: 500; }
.stack { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; font: 13px var(--mono); padding: 2px 0 10px; }
.stack .hk { padding-left: 0; }
.stack .sep { color: var(--fg-3); }
.stack a.sy { color: var(--accent); }
.stack > *:last-child { font-weight: 700; }

/* step layout: code on the left, story on the right */
.tgrid { display: grid; grid-template-columns: minmax(0, 1.15fr) minmax(0, 1fr); gap: 22px; align-items: start; }
.tcode { position: sticky; top: 112px; border: 1px solid var(--line); border-radius: 12px; overflow: hidden; background: var(--bg); }
.tfile { display: flex; justify-content: space-between; gap: 10px; padding: 8px 14px; background: var(--bg-2);
         border-bottom: 1px solid var(--line); font: 13px var(--mono); }
.tfile a { color: var(--fg); font-weight: 600; text-decoration: none; }
.tfile a:hover { color: var(--accent); }
.tfile span { color: var(--fg-3); }
.code.excerpt { padding: 8px 0 14px; max-height: calc(100vh - 230px); overflow: auto; }
.excerpt .l { cursor: default; scroll-margin-top: 0; }
.excerpt .l .n2 { flex: none; width: 4.2em; padding-right: 1.1em; text-align: right; color: var(--fg-3); text-decoration: none; user-select: none; -webkit-user-select: none; }
.excerpt .l .n2:hover { color: var(--accent); }
.excerpt .l.cx { opacity: .55; }
.excerpt .l.fx { background: var(--fxbg); box-shadow: inset 3px 0 0 var(--fxbar); }
.tnote { font-size: 16px; line-height: 1.68; padding: 4px 4px 30px; }
.tnote h2 { font-size: 23px; margin: 2px 0 12px; line-height: 1.25; }
.tstepno { margin: 4px 0 0; font: 600 12px var(--sans); color: var(--fg-3); text-transform: uppercase; letter-spacing: .06em; }
.tnote p { margin: .7em 0; }
.tnote code, .others code, .tsum code, .qa code, .q code { background: var(--bg-3); padding: .05em .3em; border-radius: 4px; font-size: .86em; }
.tnote a.sy code, .others a.sy code { color: var(--accent); }
.tnote pre, .others pre, .tsum pre, .qa pre { background: var(--bg-2); border: 1px solid var(--line); padding: 10px 12px; border-radius: 8px; overflow: auto; font: 13px/1.5 var(--mono); }
.tnote pre code, .others pre code, .qa pre code { background: none; padding: 0; }
.tnote table, .others table, .tsum table, .qa table { border-collapse: collapse; font-size: 13.5px; margin: .8em 0; width: 100%; }
.tnote th, .tnote td, .others th, .others td, .tsum th, .tsum td, .qa th, .qa td { border: 1px solid var(--line); padding: 5px 8px; text-align: left; vertical-align: top; }
.tnote th, .others th { background: var(--bg-2); }
.tnote blockquote { margin: .8em 0; padding: 4px 14px; border-left: 3px solid var(--accent); background: var(--bg-2); border-radius: 0 8px 8px 0; }
.others { margin: 20px 0 0; border: 1px solid color-mix(in srgb, var(--others) 40%, var(--line)); border-left: 5px solid var(--others);
          background: var(--othersbg); border-radius: 0 12px 12px 0; padding: 4px 16px 8px; font-size: 15px; }
.others h3 { display: flex; align-items: center; gap: 8px; margin: 10px 0 2px; font-size: 13px; text-transform: uppercase;
             letter-spacing: .05em; color: var(--others); }
.dots { display: inline-flex; gap: 3px; }
.dots i { width: 7px; height: 7px; border-radius: 50%; background: var(--others); animation: pulse 1.8s infinite; }
.dots i:nth-child(2) { animation-delay: .3s; } .dots i:nth-child(3) { animation-delay: .6s; }
@keyframes pulse { 0%, 100% { opacity: .35; } 50% { opacity: 1; } }

/* tours index and learning path */
.tours-main { max-width: 1100px; margin: 0 auto; padding: 28px clamp(16px, 4vw, 40px) 60px; }
.tours-main h1 { font-size: 32px; margin: 0 0 8px; }
.tours-main h2 { margin: 30px 0 12px; font-size: 19px; }
.lpath { display: flex; flex-wrap: wrap; gap: 6px; margin: 8px 0 6px; counter-reset: p; }
.pstop { display: inline-flex; align-items: center; gap: 7px; padding: 5px 11px 5px 6px; border: 1px solid var(--line);
         border-radius: 999px; text-decoration: none; color: var(--fg); background: var(--bg-2); font-size: 13.5px; }
.pstop span { background: var(--accent); color: #fff; border-radius: 999px; min-width: 1.7em; text-align: center; font: 700 11.5px var(--sans); padding: 2px 4px; }
.pstop:hover { border-color: var(--accent); }
.pstop.is-done span, .tcard.is-done .tnum { background: var(--m-U); }
.tcards { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 12px; }
.tcard { display: flex; gap: 12px; padding: 14px; border: 1px solid var(--line); border-radius: 14px; background: var(--bg);
         text-decoration: none; color: var(--fg); position: relative; transition: transform .12s, border-color .12s, box-shadow .12s; }
.tcard:hover { transform: translateY(-2px); border-color: var(--accent); box-shadow: var(--shadow); }
.tnum { flex: none; width: 34px; height: 34px; border-radius: 10px; background: var(--accent); color: #fff; display: grid; place-items: center; font-weight: 700; }
.tbody { display: flex; flex-direction: column; gap: 4px; min-width: 0; }
.tbody b { font-size: 15px; }
.tdesc { color: var(--fg-2); font-size: 13.5px; line-height: 1.45; }
.tmeta { color: var(--fg-3); font-size: 12px; }
.tdone { display: none; position: absolute; top: 10px; right: 12px; color: var(--m-U); font-weight: 700; }
.tcard.is-done .tdone { display: block; }
.intours { margin: 0 0 12px; padding: 8px 12px; border: 1px solid var(--line); border-radius: 10px; font-size: 13px; background: var(--bg-2); }
.intours a { display: block; margin-top: 3px; }

@media (max-width: 1000px) {
  .tgrid { grid-template-columns: minmax(0, 1fr); }
  .tcode { position: static; }
  .code.excerpt { max-height: 55vh; }
  .ttitle { display: none; }
}
@media (max-width: 760px) {
  .tour { padding: 0 12px 30px; }
  .tour-top { top: 52px; gap: 8px; }
  .tback { display: none; }
  .tnav .count { min-width: 5.5em; font-size: 12px; }
  .excerpt .l .n2 { width: 3.2em; padding-right: .8em; }
  .tnote { font-size: 15.5px; }
}
.tstep h1:focus, .tstep h2:focus { outline: none; }
.locktab a.sy code, .locktab a.sy { color: var(--accent); background: none; }

/* "running on": which stack sp points into */
:root { --st-user: #0b7a83; --st-kernel: #3346c4; --st-s0: #9b2f86; --st-none: #6b7280;
        --irq-on: #1f8a3b; --irq-off: #b4530f; --lk-spin: #b4530f; --lk-sleep: #6d4bd1; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) {
  --st-user: #63d0d8; --st-kernel: #9aa6ff; --st-s0: #f09ad9; --st-none: #a3a8b3;
  --irq-on: #6fd38a; --irq-off: #f0a463; --lk-spin: #f0a463; --lk-sleep: #b9a4ff; } }
:root[data-theme="dark"] { --st-user: #63d0d8; --st-kernel: #9aa6ff; --st-s0: #f09ad9; --st-none: #a3a8b3;
  --irq-on: #6fd38a; --irq-off: #f0a463; --lk-spin: #f0a463; --lk-sleep: #b9a4ff; }
.stk { --c: var(--st-none); display: flex; flex-wrap: wrap; align-items: center; gap: 8px 12px; margin: 14px 0 0;
       padding: 8px 12px; border: 1px solid color-mix(in srgb, var(--c) 45%, var(--line));
       border-left: 6px solid var(--c); border-radius: 12px;
       background: color-mix(in srgb, var(--c) 8%, var(--bg)); }
.stk.on-user { --c: var(--st-user); } .stk.on-kernel { --c: var(--st-kernel); }
.stk.on-boot, .stk.on-scheduler { --c: var(--st-s0); }
.stk .hk { padding: 0; }
.lanes { display: inline-flex; border: 1px solid var(--line); border-radius: 8px; overflow: hidden; background: var(--bg-2); }
.ln { display: inline-flex; flex-direction: column; justify-content: center; padding: 3px 10px; min-height: 30px;
      font: 600 12px var(--sans); color: var(--fg-3); border-left: 1px solid var(--line); line-height: 1.15;
      transition: background .35s, color .35s; }
.ln:first-child { border-left: 0; }
.ln small { font: 500 10px var(--sans); opacity: .85; }
.on-user .ln-user, .on-kernel .ln-kernel, .on-boot .ln-s0, .on-scheduler .ln-s0 { background: var(--c); color: #fff; }
.stkv { font-size: 15px; }
.stkv a.g { color: var(--c); font-weight: 700; text-decoration: none; border-bottom: 1px dotted var(--c); }
.stkv code { background: var(--bg-3); padding: .05em .3em; border-radius: 4px; font-size: .86em; }
.stkv .det { color: var(--fg-2); margin-left: 6px; font-size: 13.5px; }
.stkv .det::before { content: "· "; color: var(--fg-3); }
.sw { display: inline-flex; align-items: center; gap: 6px; font-size: 13px; color: var(--fg-2);
      padding: 2px 10px; border-radius: 999px; background: color-mix(in srgb, var(--c) 14%, var(--bg)); }
.sw code { background: var(--bg-3); padding: .05em .3em; border-radius: 4px; font-size: .9em; }
.swi { color: var(--c); font-weight: 700; }
.stk.changed { animation: stkflash 1.1s ease-out 1; }
@keyframes stkflash { 0% { box-shadow: 0 0 0 0 color-mix(in srgb, var(--c) 60%, transparent); }
                      100% { box-shadow: 0 0 0 10px transparent; } }
.trapb { font: 700 10px var(--sans); text-transform: uppercase; letter-spacing: .05em; color: var(--m-M);
         border: 1px dashed var(--m-M); border-radius: 5px; padding: 1px 5px; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .on-user .ln-user,
  :root:not([data-theme="light"]) .on-kernel .ln-kernel, :root:not([data-theme="light"]) .on-boot .ln-s0,
  :root:not([data-theme="light"]) .on-scheduler .ln-s0 { color: #111; } }
:root[data-theme="dark"] .on-user .ln-user, :root[data-theme="dark"] .on-kernel .ln-kernel,
:root[data-theme="dark"] .on-boot .ln-s0, :root[data-theme="dark"] .on-scheduler .ln-s0 { color: #111; }
@media (max-width: 640px) { .lanes { order: 3; width: 100%; } .ln { flex: 1; } }

/* stack-switch points in source views */
.l.spx .n { position: relative; color: var(--fg); font-weight: 700; }
.l.spx .n::before { content: "\21C4"; position: absolute; left: 2px; font-size: 12px; color: var(--st-none); }
.l.spx[data-spto="user"] .n::before { color: var(--st-user); }
.l.spx[data-spto="kernel"] .n::before { color: var(--st-kernel); }
.l.spx[data-spto="scheduler"] .n::before, .l.spx[data-spto="boot"] .n::before { color: var(--st-s0); }
.spbox { --c: var(--st-none); margin: 0 0 12px; padding: 8px 12px; border-left: 5px solid var(--c);
         background: color-mix(in srgb, var(--c) 9%, var(--bg)); border-radius: 0 10px 10px 0; font-size: 14px; line-height: 1.55; }
.spbox.st-user { --c: var(--st-user); } .spbox.st-kernel { --c: var(--st-kernel); }
.spbox.st-scheduler, .spbox.st-boot { --c: var(--st-s0); }
.spk { font: 700 12px var(--sans); text-transform: uppercase; letter-spacing: .04em; color: var(--c); margin-bottom: 3px; }
.spk a { color: var(--c); }
.spbox code { background: var(--bg-3); padding: .05em .3em; border-radius: 4px; font-size: .88em; }

/* figures (inline SVG, themed by CSS variables) */
.fig { margin: 16px 0 18px; padding: 12px; border: 1px solid var(--line); border-radius: 12px; background: var(--bg-2); }
.fig svg { display: block; width: 100%; height: auto; max-height: 70vh; font-family: var(--sans); }
.fig figcaption { font-size: 13.5px; color: var(--fg-2); margin-top: 8px; line-height: 1.5; }
.concept .kicker { font: 600 12px var(--sans); text-transform: uppercase; letter-spacing: .06em; color: var(--fg-3); margin: 0; }
/* concept pages: wide tables and text pictures scroll sideways instead of being clipped on phones */
.concept table { display: block; max-width: 100%; overflow-x: auto; border-collapse: collapse; font-size: 14px; margin: .8em 0; }
.concept th, .concept td { border: 1px solid var(--line); padding: 5px 8px; text-align: left; vertical-align: top; }
.concept th { background: var(--bg-2); }
.concept pre { background: var(--bg-2); border: 1px solid var(--line); padding: 10px 12px; border-radius: 8px; overflow-x: auto; font: 13px/1.5 var(--mono); }
.concept pre code { background: none; padding: 0; }
.concept details { margin: .6em 0; padding: 8px 12px; border: 1px solid var(--line); border-radius: 10px; background: var(--bg-2); }
.concept details summary { cursor: pointer; font-weight: 600; }
@media (max-width: 640px) {
  .fig { overflow-x: auto; -webkit-overflow-scrolling: touch; }
  .fig svg { min-width: 620px; max-height: none; }
  .fig figcaption { position: sticky; left: 0; }
}

/* interrupt-state strip (tours): SIE, push_off depth, intena */
.irq { --c: var(--irq-off); display: flex; flex-wrap: wrap; align-items: center; gap: 6px 12px; margin: 8px 0 0;
       padding: 6px 12px; border: 1px solid var(--line); border-left: 6px solid var(--c); border-radius: 12px;
       background: var(--bg-2); font-size: 13.5px; }
.irq .hk a { color: inherit; text-decoration: none; border-bottom: 1px dotted currentColor; }
.irq .sie { display: inline-flex; align-items: center; gap: 6px; font-weight: 700; }
.irq .sie i { width: 10px; height: 10px; border-radius: 50%; background: var(--irq-off);
              box-shadow: 0 0 0 3px color-mix(in srgb, var(--irq-off) 25%, transparent); }
.irq .sie.on { color: var(--irq-on); } .irq .sie.off { color: var(--irq-off); }
.irq .sie.on i { background: var(--irq-on); box-shadow: 0 0 0 3px color-mix(in srgb, var(--irq-on) 25%, transparent); }
.irq:has(.sie.on) { --c: var(--irq-on); }
.irq .noff { display: inline-flex; align-items: center; gap: 6px; }
.irq .pips { display: inline-flex; gap: 3px; }
.irq .pip { width: 12px; height: 12px; border-radius: 3px; border: 1.5px solid var(--lk-spin); }
.irq .pip.f { background: var(--lk-spin); }
.irq .ie { display: inline-flex; align-items: baseline; gap: 6px; font-weight: 600; }
.irq .ie small { font-weight: 400; color: var(--fg-2); }
.irq .ie.na { color: var(--fg-3); font-weight: 400; }
.irq .was { font-size: 12.5px; color: var(--fg-2); padding: 1px 8px; border-radius: 999px; background: var(--bg-3); }
.irq .det { color: var(--fg-2); flex-basis: 100%; }
.irq .det code { background: var(--bg-3); padding: .05em .3em; border-radius: 4px; font-size: .9em; }
.irq.changed .pips { animation: irqpulse 1s ease-out 1; }
@keyframes irqpulse { 0% { transform: scale(1.25); } 100% { transform: scale(1); } }
@media (prefers-reduced-motion: reduce) { .irq.changed .pips { animation: none; } }
@media (max-width: 640px) { .irq .ie small { display: none; } }

/* lock-operation markers in the source view */
.l.lkx .n { position: relative; }
.l.lkx .n::before { content: ""; position: absolute; left: 4px; top: 50%; width: 7px; height: 7px; margin-top: -4px;
                    border-radius: 2px; background: var(--lk-spin); }
.l.lkx[data-lk="sleep"] .n::before { background: var(--lk-sleep); border-radius: 50%; }
.l.lkx[data-lk="irq"] .n::before { background: transparent; border: 1.5px solid var(--irq-off); width: 5px; height: 5px; }
.lkbox { --c: var(--lk-spin); margin: 0 0 12px; padding: 8px 12px; border-left: 5px solid var(--c);
         background: color-mix(in srgb, var(--c) 9%, var(--bg)); border-radius: 0 10px 10px 0; font-size: 14px; line-height: 1.55; }
.lkbox.sleep { --c: var(--lk-sleep); } .lkbox.irq { --c: var(--irq-off); }
.lkbox .spk a { color: var(--c); }
.lkbox code { background: var(--bg-3); padding: .05em .3em; border-radius: 4px; font-size: .88em; }

/* tour tables scroll sideways on phones instead of widening the page */
@media (max-width: 640px) {
  .tnote table, .others table, .tsum table, .qa table, .note table, .gloss table {
    display: block; max-width: 100%; overflow-x: auto; width: auto; }
}

/* ------------------------------------------------------------ Test yourself */
:root { --q-ok: #1f8a3b; --q-bad: #c2410c; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) { --q-ok: #6fd38a; --q-bad: #fb923c; } }
:root[data-theme="dark"] { --q-ok: #6fd38a; --q-bad: #fb923c; }

.test-main { max-width: 920px; margin: 0 auto; padding: 28px clamp(16px, 4vw, 40px) 60px; }
.test-main h1 { font-size: 32px; margin: 0 0 8px; }
.test-main .tkicker a { color: inherit; }
.qbar { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 10px;
        margin: 16px 0 20px; padding: 10px 14px; border: 1px solid var(--line); border-radius: 12px; background: var(--bg-2); }
.qscore { font-weight: 600; }
.qfilter { display: flex; flex-wrap: wrap; gap: 6px; }
.qfilter .btn.on { background: var(--accent); color: #fff; border-color: var(--accent); }
.qcard.started .tnum { background: var(--accent-bg); }
.qcard.complete .tnum { background: var(--q-ok); color: #fff; }
.qlist { display: flex; flex-direction: column; gap: 18px; }
.qz { border: 1px solid var(--line); border-radius: 14px; padding: 16px 18px; background: var(--bg); scroll-margin-top: 70px; }
.qz.ok { border-color: color-mix(in srgb, var(--q-ok) 55%, var(--line)); }
.qz.bad { border-color: color-mix(in srgb, var(--q-bad) 55%, var(--line)); }
.qh { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; font: 600 12px var(--sans); color: var(--fg-3); }
.qn { display: inline-grid; place-items: center; min-width: 26px; height: 26px; border-radius: 8px; background: var(--bg-3); color: var(--fg); font-size: 13px; }
.qlvl { padding: 2px 8px; border-radius: 999px; background: var(--bg-3); text-transform: uppercase; letter-spacing: .04em; }
.qlvl.l1 { color: var(--q-ok); } .qlvl.l3 { color: var(--q-bad); }
.qtype { text-transform: uppercase; letter-spacing: .04em; }
.qstatus { margin-left: auto; }
.qz.was-ok .qstatus { color: var(--q-ok); } .qz.was-bad .qstatus { color: var(--q-bad); }
.qfrom { font-weight: 500; color: var(--accent); text-decoration: none; }
.qq { font-size: 16px; line-height: 1.6; }
.qq p { margin: .5em 0; }
.qq code, .qopt code, .fb code, .qfield code, .qorder code { background: var(--bg-3); padding: .05em .3em; border-radius: 4px; font-size: .9em; }
.qcode { border: 1px solid var(--line); border-radius: 10px; overflow: hidden; margin: 10px 0; }
.qfile { font: 600 12px var(--mono); padding: 6px 12px; background: var(--bg-2); border-bottom: 1px solid var(--line); }
.qcode .code.excerpt { max-height: 420px; }
.qz[data-type="line"] .qcode .l { cursor: pointer; opacity: 1; }
.qz[data-type="line"] .qcode .l:hover { background: var(--bg-3); }
.qcode .l.picked { background: var(--accent-bg); box-shadow: inset 3px 0 0 var(--accent); }
.qcode .l.right { background: color-mix(in srgb, var(--q-ok) 16%, var(--bg)); box-shadow: inset 3px 0 0 var(--q-ok); }
.qcode .l.wrong { background: color-mix(in srgb, var(--q-bad) 16%, var(--bg)); box-shadow: inset 3px 0 0 var(--q-bad); }
.qopts { display: flex; flex-direction: column; gap: 6px; margin: 8px 0; }
.qopt { display: flex; gap: 10px; align-items: flex-start; padding: 8px 12px; border: 1px solid var(--line); border-radius: 10px; cursor: pointer; line-height: 1.5; }
.qopt:hover { background: var(--bg-2); }
.qopt input { margin-top: .3em; flex: none; }
.qopt.right { border-color: var(--q-ok); background: color-mix(in srgb, var(--q-ok) 10%, var(--bg)); }
.qopt.wrong { border-color: var(--q-bad); background: color-mix(in srgb, var(--q-bad) 10%, var(--bg)); }
.qtf { flex-direction: row; } .qtf .qopt { flex: 1; }
.qsub { margin: 10px 0 0; font-weight: 600; }
.qnum { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; margin: 8px 0; }
.qnum input { font: 16px var(--mono); padding: 8px 10px; border: 1px solid var(--line); border-radius: 8px; background: var(--bg); color: var(--fg); width: 14em; max-width: 100%; }
.qhint { font-size: 13px; color: var(--fg-3); }
.qorder { list-style: none; counter-reset: qo; padding: 0; margin: 8px 0; display: flex; flex-direction: column; gap: 6px; }
.qorder li { counter-increment: qo; display: flex; align-items: center; gap: 10px; padding: 8px 10px; border: 1px solid var(--line); border-radius: 10px; background: var(--bg-2); }
.qorder li::before { content: counter(qo); font-weight: 700; color: var(--fg-3); min-width: 1.4em; }
.qotext { flex: 1; line-height: 1.45; }
.qomove { display: flex; gap: 4px; }
.qomove button { width: 34px; height: 34px; border: 1px solid var(--line); border-radius: 8px; background: var(--bg); color: var(--fg); cursor: pointer; font-size: 16px; }
.qz.done .qomove { visibility: hidden; }
.qorder li.right { border-color: var(--q-ok); } .qorder li.wrong { border-color: var(--q-bad); }
.qfields { display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: 8px 14px; margin: 8px 0; }
.qmatch { grid-template-columns: 1fr; }
.qfield { display: flex; flex-direction: column; gap: 4px; padding: 8px 10px; border: 1px solid var(--line); border-radius: 10px; }
.qfield span { font-weight: 600; font-size: 14px; }
.qfield select { font: 14px var(--sans); padding: 6px 8px; border: 1px solid var(--line); border-radius: 8px; background: var(--bg); color: var(--fg); max-width: 100%; }
.qfield.right { border-color: var(--q-ok); } .qfield.wrong { border-color: var(--q-bad); }
.qval { font-size: 15px; }
.qpick { font-size: 14px; color: var(--fg-2); }
.qbtns { display: flex; gap: 8px; margin-top: 10px; }
.qfb { margin-top: 12px; }
.fb { padding: 12px 14px; border-radius: 10px; border-left: 5px solid var(--c); background: color-mix(in srgb, var(--c) 8%, var(--bg)); line-height: 1.6; }
.fb.ok { --c: var(--q-ok); } .fb.bad { --c: var(--q-bad); } .fb.need { --c: var(--fg-3); }
.fb .fbh { font-weight: 700; color: var(--c); margin: 0 0 6px; }
.fb h4 { margin: 12px 0 4px; font-size: 13px; text-transform: uppercase; letter-spacing: .04em; color: var(--fg-2); }
.fb p { margin: .4em 0; }
.fb .fbright { border-top: 1px dashed var(--line); padding-top: 4px; }
.qcorr { margin: .3em 0 .6em; padding-left: 1.4em; }
.qnav { display: flex; justify-content: space-between; gap: 10px; flex-wrap: wrap; margin-top: 28px; padding-top: 14px; border-top: 1px solid var(--line); }
@media (max-width: 640px) {
  .qz { padding: 12px; } .qtf { flex-direction: column; }
  .qfields { grid-template-columns: 1fr; }
  .qcode .code.excerpt { max-height: 50vh; }
}

/* header: four section links must fit at phone width */
@media (max-width: 760px) {
  .top { gap: 8px; padding: 0 10px; }
  .search { min-width: 0; }
  .toplink { font-size: 12.5px; }
}
@media (max-width: 520px) { .tlw { display: none; } }
.qlist > *, .qz, .qans, .qcode { min-width: 0; max-width: 100%; }
.qcode .code.excerpt { overflow-x: auto; }
.qfield { min-width: 0; } .qfield select { width: 100%; min-width: 0; text-overflow: ellipsis; }
.qfields { grid-template-columns: repeat(auto-fill, minmax(min(250px, 100%), 1fr)); }

/* ------------------------------------------------------------ extension labs */
.lab .labhead h1 { margin-bottom: 4px; }
.stars { color: #d39e00; letter-spacing: 1px; }
.labmeta { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(320px, 100%), 1fr)); gap: 16px;
           margin: 14px 0; padding: 14px; border: 1px solid var(--line); border-radius: 12px; background: var(--bg-2); }
.labmeta h3 { margin: 0 0 6px; font-size: 14px; text-transform: uppercase; letter-spacing: .04em; color: var(--fg-2); }
.labmeta ul { margin: 0; padding-left: 1.2em; }
pre.cmd, pre.symptom { font: 13px/1.5 var(--mono); background: var(--bg-3); padding: 10px 12px; border-radius: 8px;
                       overflow-x: auto; max-width: 100%; white-space: pre; }
pre.symptom { border-left: 4px solid var(--q-bad); }
.labnav { position: sticky; top: 52px; z-index: 5; display: flex; flex-wrap: wrap; gap: 4px 14px; padding: 8px 0;
          background: var(--bg); border-bottom: 1px solid var(--line); margin-bottom: 8px; font-size: 14px; }
.labnav a { color: var(--fg-2); text-decoration: none; }
.labnav a:hover { color: var(--accent); }
.labsec { scroll-margin-top: 100px; padding-top: 6px; }
.labsec h2 { margin-top: 28px; }
.think, .bug { border: 1px solid var(--line); border-radius: 14px; padding: 14px 16px; margin: 14px 0; background: var(--bg); }
.think h3, .bug h3 { display: flex; gap: 10px; align-items: center; margin: 0 0 6px; font-size: 17px; }
.hint { margin: 8px 0; padding: 8px 12px; border-left: 4px solid var(--accent); background: var(--accent-bg); border-radius: 0 8px 8px 0; }
.ans, .why { margin-top: 10px; padding: 10px 14px; border-left: 4px solid var(--q-ok);
             background: color-mix(in srgb, var(--q-ok) 8%, var(--bg)); border-radius: 0 10px 10px 0; }
.ans h4 { margin: 0 0 4px; }
.checks { margin-top: 12px; } .checks h4 { margin: 6px 0; }
.commits { padding-left: 1.3em; } .commits li { margin: 6px 0; }
.commits summary { cursor: pointer; } .sha { font: 12px var(--mono); color: var(--fg-3); }
.dfile { font: 600 12.5px var(--mono); margin: 10px 0 4px; }
.code.diff { border: 1px solid var(--line); border-radius: 8px; overflow-x: auto; font: 12.5px/1.55 var(--mono); padding: 4px 0; }
.dl { display: flex; white-space: pre; min-width: max-content; }
.dl .dn { flex: none; width: 3.4em; text-align: right; padding-right: .6em; color: var(--fg-3); user-select: none; -webkit-user-select: none; }
.dl .t { padding-left: .6em; padding-right: 12px; }
.dl.add { background: color-mix(in srgb, var(--q-ok) 13%, var(--bg)); }
.dl.add .t::before { content: "+"; margin-left: -.6em; color: var(--q-ok); }
.dl.del { background: color-mix(in srgb, var(--q-bad) 13%, var(--bg)); }
.dl.del .t::before { content: "−"; margin-left: -.6em; color: var(--q-bad); }
.dl.hunk { color: var(--fg-3); background: var(--bg-2); }
.tdiff { margin-top: 10px; } .tdiff summary { cursor: pointer; font-size: 13px; padding: 4px 0; }
.tdiff .code.diff { max-height: 50vh; overflow: auto; }
.labcard.planned { opacity: .55; }
.tfile .sha { margin-left: 6px; }
.labmeta > div { min-width: 0; } .lab .bugchange pre, .lab .ans pre, .lab .qq pre { max-width: 100%; overflow-x: auto; }
.lab pre { max-width: 100%; overflow-x: auto; background: var(--bg-3); padding: 10px 12px; border-radius: 8px; font: 13px/1.5 var(--mono); } .lab pre code { background: none; padding: 0; } .lab .labsec, .lab .think, .lab .bug { min-width: 0; max-width: 100%; }
.lab table { display: block; max-width: 100%; overflow-x: auto; border-collapse: collapse; } .lab th, .lab td { border: 1px solid var(--line); padding: 4px 8px; text-align: left; vertical-align: top; }

/* ------------------------------------------------------------ about the creator */
:root { --ab-a: #2456b8; --ab-b: #9b2f86; --ab-c: #0b7a83; --ab-gold: #b7791f; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) { --ab-a: #7aa7ff; --ab-b: #f09ad9; --ab-c: #63d0d8; --ab-gold: #f2c46d; } }
:root[data-theme="dark"] { --ab-a: #7aa7ff; --ab-b: #f09ad9; --ab-c: #63d0d8; --ab-gold: #f2c46d; }
body.about-page { height: auto; min-height: 100%; }
.ab-hero { position: relative; overflow: hidden; padding: clamp(28px, 6vw, 72px) clamp(16px, 5vw, 56px) 36px;
  background: radial-gradient(1200px 500px at 15% -10%, color-mix(in srgb, var(--ab-a) 22%, transparent), transparent 60%),
              radial-gradient(900px 500px at 95% 10%, color-mix(in srgb, var(--ab-b) 18%, transparent), transparent 60%),
              radial-gradient(800px 400px at 50% 120%, color-mix(in srgb, var(--ab-c) 16%, transparent), transparent 60%), var(--bg);
  border-bottom: 1px solid var(--line); }
.ab-glow { position: absolute; inset: -40%; background: conic-gradient(from 0deg, transparent, color-mix(in srgb, var(--ab-a) 10%, transparent), transparent 30%);
  animation: abspin 40s linear infinite; pointer-events: none; }
@keyframes abspin { to { transform: rotate(360deg); } }
.ab-hero-in { position: relative; max-width: 1100px; margin: 0 auto; display: grid; grid-template-columns: auto 1fr; gap: clamp(20px, 4vw, 56px); align-items: center; }
.ab-photo { position: relative; width: clamp(150px, 22vw, 250px); aspect-ratio: 349 / 481; border-radius: 28px; padding: 5px;
  background: linear-gradient(140deg, var(--ab-a), var(--ab-b) 55%, var(--ab-c)); box-shadow: 0 24px 60px -18px color-mix(in srgb, var(--ab-a) 55%, transparent); }
.ab-photo img { display: block; width: 100%; height: 100%; object-fit: cover; border-radius: 23px; }
.ab-kicker { font: 700 12.5px var(--sans); letter-spacing: .14em; text-transform: uppercase; color: var(--ab-a); margin: 0 0 8px; }
.ab-id h1 { font-size: clamp(34px, 6vw, 64px); line-height: 1.02; margin: 0 0 14px; letter-spacing: -.02em;
  background: linear-gradient(100deg, var(--fg) 30%, var(--ab-a) 70%, var(--ab-b)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.ab-roles { list-style: none; padding: 0; margin: 0 0 14px; font-size: clamp(15px, 1.8vw, 18px); line-height: 1.55; color: var(--fg); }
.ab-roles li::before { content: "◆"; color: var(--ab-gold); font-size: .7em; margin-right: 10px; vertical-align: .15em; }
.ab-tag { font-size: 16px; color: var(--fg-2); max-width: 62ch; line-height: 1.6; margin: 0 0 18px; }
.ab-links { display: flex; flex-wrap: wrap; gap: 8px; }
.ab-link { display: inline-flex; align-items: center; gap: 8px; padding: 8px 14px; border-radius: 999px; border: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg) 80%, transparent); color: var(--fg); text-decoration: none; font-size: 14px; transition: transform .15s, border-color .15s; }
.ab-link svg { width: 17px; height: 17px; color: var(--ab-a); }
.ab-link:hover { transform: translateY(-2px); border-color: var(--ab-a); }
.ab-stats { position: relative; max-width: 1100px; margin: 34px auto 0; display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 12px; }
.ab-stat { padding: 16px 14px; border-radius: 16px; border: 1px solid var(--line); background: color-mix(in srgb, var(--bg) 85%, transparent);
  backdrop-filter: blur(6px); text-align: center; }
.ab-stat b { display: block; font-size: clamp(28px, 4vw, 40px); line-height: 1; font-variant-numeric: tabular-nums;
  background: linear-gradient(120deg, var(--ab-a), var(--ab-b)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.ab-stat span { display: block; font-weight: 700; margin-top: 6px; font-size: 14px; }
.ab-stat small { display: block; color: var(--fg-3); font-size: 12px; margin-top: 2px; }
.ab-main { max-width: 1100px; margin: 0 auto; padding: 8px clamp(16px, 5vw, 56px) 80px; }
.ab-sec { padding-top: 46px; scroll-margin-top: 60px; }
.ab-sec h2 { font-size: clamp(24px, 3vw, 32px); margin: 0 0 18px; letter-spacing: -.01em; }
.ab-sk { font: 700 12px var(--sans); letter-spacing: .12em; text-transform: uppercase; color: var(--ab-b); margin: 0 0 6px; }
.ab-why { position: relative; padding: 22px 26px; border-radius: 18px; font-size: 17px; line-height: 1.7;
  background: linear-gradient(135deg, color-mix(in srgb, var(--ab-a) 9%, var(--bg)), color-mix(in srgb, var(--ab-b) 7%, var(--bg)));
  border: 1px solid color-mix(in srgb, var(--ab-a) 30%, var(--line)); }
.ab-why p { margin: 0; }
.ab-prose { font-size: 16.5px; line-height: 1.75; max-width: 75ch; color: var(--fg); }
.ab-books { display: grid; gap: 16px; }
.ab-book { display: grid; grid-template-columns: 120px 1fr; gap: 20px; align-items: center; padding: 18px; border: 1px solid var(--line); border-radius: 18px; background: var(--bg); }
.ab-feature { border-color: color-mix(in srgb, var(--ab-gold) 60%, var(--line)); box-shadow: 0 14px 40px -24px color-mix(in srgb, var(--ab-gold) 70%, transparent); }
.ab-cover { aspect-ratio: 2 / 3; border-radius: 6px 10px 10px 6px; padding: 12px 10px; display: flex; flex-direction: column; justify-content: space-between;
  color: #fff; background: linear-gradient(160deg, #1d2b53, #3346c4 60%, #9b2f86); box-shadow: inset 6px 0 0 rgba(0,0,0,.25), 0 10px 24px -10px rgba(0,0,0,.5); }
.ab-book:nth-child(2) .ab-cover { background: linear-gradient(160deg, #0f3b3f, #0b7a83 60%, #b7791f); }
.ab-cover span { font: 800 13px/1.25 var(--sans); }
.ab-cover small { font-size: 9.5px; opacity: .85; letter-spacing: .06em; text-transform: uppercase; }
.ab-status { display: inline-block; margin: 0 0 6px; padding: 2px 10px; border-radius: 999px; font: 700 11px var(--sans); text-transform: uppercase;
  letter-spacing: .06em; color: var(--ab-gold); border: 1px solid color-mix(in srgb, var(--ab-gold) 60%, var(--line)); }
.ab-book h3 { margin: 0 0 6px; font-size: 18px; line-height: 1.35; }
.ab-meta { margin: 0; color: var(--fg-2); font-size: 14px; line-height: 1.5; }
.ab-note { margin: 8px 0 0; font-weight: 600; color: var(--ab-a); }
.ab-tools { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 14px; }
.ab-tool { display: flex; flex-direction: column; padding: 18px; border-radius: 16px; border: 1px solid var(--line); background: var(--bg);
  color: var(--fg); text-decoration: none; transition: transform .15s, box-shadow .15s, border-color .15s; }
.ab-tool:hover { transform: translateY(-3px); border-color: var(--ab-c); box-shadow: 0 16px 36px -22px color-mix(in srgb, var(--ab-c) 70%, transparent); }
.ab-tool h3 { margin: 0 0 6px; font-size: 17px; }
.ab-tool p { margin: 0 0 12px; color: var(--fg-2); font-size: 14px; line-height: 1.55; flex: 1; }
.ab-go { font: 600 13px var(--mono); color: var(--ab-c); }
.ab-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 14px; }
.ab-card { padding: 18px; border-radius: 16px; border: 1px solid var(--line); background: var(--bg); }
.ab-card h3, .ab-tl h3 { margin: 2px 0 2px; font-size: 17px; }
.ab-card ul { margin: 10px 0 0; padding-left: 1.1em; font-size: 14.5px; line-height: 1.55; color: var(--fg-2); }
.ab-years { margin: 0; font: 700 12px var(--mono); color: var(--ab-a); }
.ab-org { margin: 0; font-style: italic; color: var(--fg-2); }
.ab-tl { list-style: none; margin: 0; padding: 0 0 0 22px; border-left: 2px solid color-mix(in srgb, var(--ab-a) 40%, var(--line)); }
.ab-tl li { position: relative; display: block; padding: 0 0 22px 12px; }
.ab-tl .ab-dot { position: absolute; left: -31px; top: 4px; width: 14px; height: 14px; border-radius: 50%; background: var(--bg);
  border: 3px solid var(--ab-a); box-shadow: 0 0 0 4px color-mix(in srgb, var(--ab-a) 15%, transparent); }
.ab-tl p:last-child { margin: 6px 0 0; color: var(--fg-2); font-size: 14.5px; line-height: 1.6; }
.ab-sub { color: var(--fg-2); margin: -8px 0 14px; }
.ab-pats, .ab-pubs { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.ab-pats li { padding: 12px 14px; border: 1px solid var(--line); border-radius: 12px; background: var(--bg); line-height: 1.5; }
.ab-num { display: block; font: 700 12px var(--mono); color: var(--ab-gold); margin-bottom: 4px; }
.ab-pubs li { display: grid; grid-template-columns: 118px 1fr; gap: 12px; align-items: baseline; padding: 10px 0; border-bottom: 1px solid var(--line); }
.ab-pt { font: 700 11px var(--sans); text-transform: uppercase; letter-spacing: .05em; color: var(--ab-b); }
.ab-pubs a { color: var(--fg); text-decoration: none; border-bottom: 1px dotted var(--ab-a); }
.ab-pubs a:hover { color: var(--ab-a); }
.ab-pubs small { display: block; color: var(--fg-3); margin-top: 2px; }
.ab-honors { margin: 0; padding-left: 1.2em; line-height: 1.8; }
.ab-chips { display: flex; flex-wrap: wrap; gap: 8px; }
.ab-chip { padding: 6px 12px; border-radius: 999px; font-size: 13.5px; border: 1px solid color-mix(in srgb, var(--ab-a) 35%, var(--line));
  background: color-mix(in srgb, var(--ab-a) 7%, var(--bg)); }
.ab-reveal { opacity: 0; transform: translateY(16px); transition: opacity .6s ease, transform .6s ease; }
.ab-reveal.in { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) { .ab-glow { animation: none; } .ab-reveal { opacity: 1; transform: none; transition: none; } }
@media (max-width: 680px) {
  .ab-hero-in { grid-template-columns: 1fr; justify-items: center; text-align: center; }
  .ab-roles li::before { display: none; } .ab-links { justify-content: center; }
  .ab-book { grid-template-columns: 84px 1fr; gap: 14px; }
  .ab-pubs li { grid-template-columns: 1fr; gap: 2px; }
}
.ab-top { color: var(--ab-a); font-weight: 600; }

/* header section links: one strip that scrolls sideways on narrow screens instead of the page */
.toplinks { display: flex; align-items: center; gap: 12px; min-width: 0; }
@media (max-width: 760px) {
  .toplinks { flex: 1 1 auto; overflow-x: auto; scrollbar-width: none; gap: 10px; padding: 0 2px;
              -webkit-mask-image: linear-gradient(90deg, #000 85%, transparent); mask-image: linear-gradient(90deg, #000 85%, transparent); }
  .toplinks::-webkit-scrollbar { display: none; }
  .search { flex: 0 1 120px; }
}
@media (max-width: 420px) { .search { flex-basis: 84px; } }
.creator { display: flex; align-items: center; gap: 16px; margin: 22px 0 6px; padding: 14px 18px; border-radius: 16px; text-decoration: none; color: var(--fg);
  border: 1px solid color-mix(in srgb, var(--ab-a) 35%, var(--line));
  background: linear-gradient(120deg, color-mix(in srgb, var(--ab-a) 8%, var(--bg)), color-mix(in srgb, var(--ab-b) 7%, var(--bg))); }
.creator img { width: 56px; height: 72px; object-fit: cover; border-radius: 12px; flex: none; box-shadow: 0 0 0 3px color-mix(in srgb, var(--ab-a) 40%, transparent); }
.creator small { display: block; font: 700 11px var(--sans); text-transform: uppercase; letter-spacing: .1em; color: var(--ab-b); }
.creator b { display: block; font-size: 19px; }
.creator span span { display: block; color: var(--fg-2); font-size: 14px; }
.creator:hover b { color: var(--ab-a); }
.ab-tstat { align-self: flex-start; margin: 0 0 8px !important; padding: 2px 10px; border-radius: 999px; font: 700 11px var(--sans) !important;
  text-transform: uppercase; letter-spacing: .06em; color: var(--fg-2) !important; border: 1px solid var(--line); flex: none !important; }
.ab-tstat.live { color: var(--ab-c) !important; border-color: color-mix(in srgb, var(--ab-c) 60%, var(--line)); }
.ab-soon { cursor: default; }
.ab-soon:hover { transform: none; box-shadow: none; border-color: var(--line); }
.ab-tpaper { font-size: 13px !important; flex: none !important; border-top: 1px dashed var(--line); padding-top: 10px; }
/* teaching tools: screenshot cards */
.ab-tools { grid-template-columns: repeat(auto-fit, minmax(min(100%, 420px), 1fr)); gap: 18px; }
.ab-tool { padding: 0; overflow: hidden; }
.ab-tbody { display: flex; flex-direction: column; flex: 1; padding: 16px 18px 18px; }
.ab-shot { margin: 0; position: relative; border-bottom: 1px solid var(--line); background: #0d1117; }
.ab-shot img { display: block; width: 100%; height: auto; aspect-ratio: 16 / 10; object-fit: cover; object-position: top left;
  transition: transform .4s ease; }
.ab-tool:hover .ab-shot img { transform: scale(1.025); }
.ab-soon:hover .ab-shot img { transform: none; }
.ab-shot figcaption { position: absolute; left: 0; right: 0; bottom: 0; padding: 18px 14px 8px; font-size: 12.5px; color: #fff;
  background: linear-gradient(transparent, rgba(0,0,0,.72)); }
.ab-soon .ab-shot img { filter: saturate(.92); }
.foot.lic { font-size: 12.5px; color: var(--fg-3); margin-top: 4px; }
.ab-lic { font-size: 15px; }
.ab-lic li { margin: 6px 0; }