/* Learn RAG. Typographic, near monochrome, hairline rules, one accent.
   No external fonts, no gradients, no shadows, no rounded cards. */

:root {
  --paper:      #fcfcfa;
  --paper2:     #f4f4f0;
  --ink:        #16181c;
  --ink2:       #3d434c;
  --ink3:       #7b828d;
  --rule:       #ddddd6;
  --rule2:      #c3c3ba;
  --accent:     #0f4fd8;
  --accent-dim: #dde5fa;
  --live:       #0a6b4a;
  --flag:       #a8420d;
  --stop:       #b3231f;

  --serif: Charter, "Bitstream Charter", "Sitka Text", Cambria, Georgia, "Times New Roman", serif;
  --mono: "Berkeley Mono", ui-monospace, SFMono-Regular, "Cascadia Mono", "DejaVu Sans Mono", Consolas, monospace;

  --measure: 34rem;
}

:root[data-theme="dark"] {
  --paper:      #0e0f12;
  --paper2:     #16181c;
  --ink:        #e4e4df;
  --ink2:       #b0b4bb;
  --ink3:       #767c86;
  --rule:       #262930;
  --rule2:      #3a3e47;
  --accent:     #7aa7ff;
  --accent-dim: #16233d;
  --live:       #4fc79a;
  --flag:       #e39355;
  --stop:       #f0736d;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font: 400 17px/1.62 var(--serif);
  font-feature-settings: "kern" 1, "liga" 1, "onum" 1;
  -webkit-font-smoothing: antialiased;
}

/* ============ frame ============ */
#shell { display: flex; align-items: flex-start; }

#sidebar {
  width: 15.5rem;
  flex: 0 0 auto;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  border-right: 1px solid var(--rule);
  padding: 2rem 0 3rem;
  scrollbar-width: thin;
}

#brand { padding: 0 1.5rem 1.4rem; }
#brand a { text-decoration: none; color: inherit; }
#brand .mark {
  font: 400 0.68rem/1 var(--mono);
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--ink3);
  display: block;
  margin-bottom: 0.5rem;
}
#brand h1 {
  margin: 0;
  font: 400 1.28rem/1.15 var(--serif);
  letter-spacing: -0.015em;
}
#brand h1 em { font-style: italic; color: var(--accent); }

#prog { padding: 0 1.5rem 1.3rem; }
#progline {
  height: 1px;
  background: var(--rule2);
  position: relative;
  margin-bottom: 0.45rem;
}
#progfill {
  position: absolute;
  left: 0; top: -1px; height: 3px;
  background: var(--accent);
  width: 0;
  transition: width 0.45s cubic-bezier(.2,.7,.3,1);
}
#progtext {
  font: 400 0.64rem/1 var(--mono);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink3);
}

nav ol { list-style: none; margin: 0; padding: 0; }
nav .part {
  font: 400 0.62rem/1 var(--mono);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--ink3);
  padding: 1.35rem 1.5rem 0.5rem;
}
nav a {
  display: grid;
  grid-template-columns: 1.55rem 1fr;
  gap: 0.1rem;
  padding: 0.32rem 1.5rem 0.32rem 1.5rem;
  text-decoration: none;
  color: var(--ink2);
  font-size: 0.94rem;
  line-height: 1.32;
  border-left: 2px solid transparent;
  transition: color 0.15s, border-color 0.15s;
}
nav a .n {
  font: 400 0.7rem/1.7 var(--mono);
  color: var(--ink3);
  transition: color 0.15s;
}
nav a:hover { color: var(--ink); }
nav a:hover .n { color: var(--accent); }
nav a.active { color: var(--ink); border-left-color: var(--accent); }
nav a.active .n { color: var(--accent); }
nav a.done .n { color: var(--live); }
nav a.done .n::after { content: "\00b7"; margin-left: 1px; }

#main { flex: 1 1 auto; min-width: 0; }

#topbar {
  display: flex;
  align-items: baseline;
  gap: 1rem;
  padding: 1.1rem 3rem 1.1rem;
  border-bottom: 1px solid var(--rule);
  position: sticky; top: 0; z-index: 30;
  background: var(--paper);
}
#crumb {
  font: 400 0.66rem/1 var(--mono);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink3);
}
#topbar .gap { flex: 1; }
.tbtn {
  background: none; border: none; padding: 0;
  font: 400 0.66rem/1 var(--mono);
  letter-spacing: 0.14em; text-transform: uppercase;
  color: var(--ink3); cursor: pointer;
  border-bottom: 1px solid transparent;
  transition: color 0.15s, border-color 0.15s;
}
.tbtn:hover { color: var(--ink); border-bottom-color: var(--rule2); }
#menubtn { display: none; }

article {
  max-width: var(--measure);
  padding: 3.2rem 3rem 7rem;
  margin: 0;
  margin-left: 5.5rem;
}

/* ============ text ============ */
.eyebrow {
  font: 400 0.66rem/1 var(--mono);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--ink3);
  margin: 0 0 0.8rem;
}
h2 {
  font: 400 2.05rem/1.14 var(--serif);
  letter-spacing: -0.022em;
  margin: 0 0 0.7rem;
}
.lede {
  font: 400 1.16rem/1.55 var(--serif);
  color: var(--ink2);
  margin: 0 0 2.2rem;
  padding-bottom: 1.6rem;
  border-bottom: 1px solid var(--rule);
}
h3 {
  font: 600 1.16rem/1.3 var(--serif);
  letter-spacing: -0.008em;
  margin: 2.9rem 0 0.75rem;
  position: relative;
}
h3 .sn {
  position: absolute;
  left: -3.6rem;
  top: 0.28rem;
  font: 400 0.68rem/1 var(--mono);
  color: var(--ink3);
  letter-spacing: 0.06em;
}
h4 {
  font: 600 1rem/1.35 var(--serif);
  margin: 1.9rem 0 0.5rem;
}
p { margin: 0 0 1.05rem; }
ul, ol { margin: 0 0 1.2rem; padding-left: 1.35rem; }
li { margin-bottom: 0.5rem; padding-left: 0.15rem; }
li::marker { color: var(--ink3); }
strong { font-weight: 600; }
em { font-style: italic; }

a { color: var(--accent); text-decoration: none; border-bottom: 1px solid var(--accent-dim); transition: border-color 0.15s; }
a:hover { border-bottom-color: var(--accent); }

code {
  font: 400 0.86em/1.4 var(--mono);
  background: var(--paper2);
  padding: 0.08em 0.32em;
  border-radius: 2px;
  color: var(--ink);
}
pre {
  font: 400 0.79rem/1.62 var(--mono);
  background: var(--paper2);
  border-left: 2px solid var(--rule2);
  padding: 0.9rem 1.1rem;
  overflow-x: auto;
  margin: 0 0 1.3rem;
}
pre code { background: none; padding: 0; font-size: inherit; }
pre .c { color: var(--ink3); font-style: italic; }
pre .s { color: var(--live); }
pre .k { color: var(--accent); }

blockquote {
  margin: 1.5rem 0;
  padding: 0 0 0 1.15rem;
  border-left: 2px solid var(--rule2);
  font-style: italic;
  color: var(--ink2);
}
blockquote p:last-child { margin-bottom: 0; }
blockquote cite { display: block; font-style: normal; font-size: 0.82rem; color: var(--ink3); margin-top: 0.5rem; font-family: var(--mono); }

hr { border: none; border-top: 1px solid var(--rule); margin: 2.6rem 0; }

/* ============ tables ============ */
.tw { overflow-x: auto; margin: 0 0 1.4rem; }
table { border-collapse: collapse; width: 100%; font-size: 0.9rem; line-height: 1.45; }
caption {
  caption-side: top;
  text-align: left;
  font: 400 0.66rem/1.5 var(--mono);
  letter-spacing: 0.13em;
  text-transform: uppercase;
  color: var(--ink3);
  padding-bottom: 0.5rem;
}
th, td { padding: 0.42rem 0.85rem 0.42rem 0; text-align: left; vertical-align: top; border-bottom: 1px solid var(--rule); }
thead th { border-bottom: 1px solid var(--rule2); font-weight: 600; font-size: 0.82rem; }
tbody tr:last-child td { border-bottom: none; }
td.num, th.num { font-family: var(--mono); font-size: 0.82rem; font-variant-numeric: tabular-nums; }

/* ============ margin notes and flags ============ */
.aside {
  border-left: 2px solid var(--rule2);
  padding: 0.15rem 0 0.15rem 1.15rem;
  margin: 1.5rem 0;
  font-size: 0.94rem;
  color: var(--ink2);
}
.aside .l {
  display: block;
  font: 400 0.62rem/1 var(--mono);
  letter-spacing: 0.19em;
  text-transform: uppercase;
  color: var(--ink3);
  margin-bottom: 0.5rem;
}
.aside.key { border-left-color: var(--accent); }
.aside.key .l { color: var(--accent); }
.aside.flag { border-left-color: var(--flag); }
.aside.flag .l { color: var(--flag); }
.aside.stop { border-left-color: var(--stop); }
.aside.stop .l { color: var(--stop); }
.aside p:last-child { margin-bottom: 0; }

/* ============ labs ============ */
.lab { margin: 2.4rem 0; border-top: 1px solid var(--ink); padding-top: 0.7rem; }
.lab > .head { display: flex; align-items: baseline; gap: 0.75rem; margin-bottom: 0.3rem; }
.lab > .head .l {
  font: 400 0.62rem/1 var(--mono);
  letter-spacing: 0.19em; text-transform: uppercase;
  color: var(--accent);
}
.lab > .head h4 { margin: 0; font-size: 1rem; font-weight: 600; }
.lab > .intro { font-size: 0.94rem; color: var(--ink2); margin-bottom: 1.1rem; }
.lab .panel { border: 1px solid var(--rule); padding: 1.1rem 1.2rem; background: var(--paper2); }
.lab .panel > :last-child { margin-bottom: 0; }
.lab .after { font-size: 0.94rem; margin-top: 1.1rem; }

.ctl { display: flex; flex-wrap: wrap; gap: 1.1rem; align-items: flex-end; margin-bottom: 1rem; }
.ctl .f { flex: 1 1 9rem; min-width: 7rem; }
.ctl label, .fieldlbl {
  display: block;
  font: 400 0.62rem/1 var(--mono);
  letter-spacing: 0.14em; text-transform: uppercase;
  color: var(--ink3); margin-bottom: 0.4rem;
}
.ctl label .v { color: var(--accent); float: right; letter-spacing: 0; text-transform: none; }

input[type=text], input[type=number], textarea, select {
  width: 100%;
  background: var(--paper);
  border: 1px solid var(--rule2);
  color: var(--ink);
  font: 400 0.92rem/1.4 var(--serif);
  padding: 0.4rem 0.55rem;
  border-radius: 0;
  transition: border-color 0.15s;
}
input[type=number] { font-family: var(--mono); font-size: 0.85rem; }
textarea { font: 400 0.78rem/1.6 var(--mono); resize: vertical; }
input:focus, textarea:focus, select:focus { outline: none; border-color: var(--accent); }
input[type=range] {
  width: 100%; accent-color: var(--accent);
  height: 1.1rem; background: none; cursor: pointer;
}
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.presets { display: flex; flex-wrap: wrap; gap: 0.4rem 0.9rem; margin-bottom: 0.9rem; }
.preset {
  background: none; border: none; padding: 0 0 1px;
  font: 400 0.78rem/1.4 var(--mono);
  color: var(--ink2); cursor: pointer;
  border-bottom: 1px solid var(--rule2);
  transition: color 0.15s, border-color 0.15s;
}
.preset:hover { color: var(--accent); border-bottom-color: var(--accent); }
.presets .pl {
  font: 400 0.62rem/1.6 var(--mono);
  letter-spacing: 0.14em; text-transform: uppercase; color: var(--ink3);
}

.btn {
  background: none;
  border: 1px solid var(--ink);
  color: var(--ink);
  font: 400 0.72rem/1 var(--mono);
  letter-spacing: 0.13em; text-transform: uppercase;
  padding: 0.5rem 0.9rem; cursor: pointer;
  transition: background 0.15s, color 0.15s;
}
.btn:hover { background: var(--ink); color: var(--paper); }

/* result rows */
.rows { font-variant-numeric: tabular-nums; }
.rrow { display: grid; grid-template-columns: 1.5rem 1fr 3.4rem; gap: 0.6rem; align-items: center; padding: 0.12rem 0; }
.rrow .rk { font: 400 0.7rem/1 var(--mono); color: var(--ink3); text-align: right; }
.rrow .track { position: relative; height: 1.45rem; border-bottom: 1px solid var(--rule); }
.rrow .fill { position: absolute; left: 0; top: 0; bottom: 0; background: var(--accent-dim); transition: width 0.3s cubic-bezier(.2,.7,.3,1); }
.rrow .txt { position: relative; padding: 0.18rem 0.4rem 0 0; font-size: 0.86rem; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.rrow .sc { font: 400 0.74rem/1 var(--mono); color: var(--ink2); text-align: right; }
.rrow.nil .fill { background: none; }
.rrow.nil .txt, .rrow.nil .sc { color: var(--ink3); }
.rrow.mark .fill { background: color-mix(in srgb, var(--live) 16%, transparent); }

/* chunk viewer */
.chunks { display: flex; flex-direction: column; }
.chk { border-bottom: 1px solid var(--rule); padding: 0.55rem 0; font: 400 0.78rem/1.6 var(--mono); }
.chk:last-child { border-bottom: none; }
.chk .m { display: block; font-size: 0.62rem; letter-spacing: 0.14em; text-transform: uppercase; color: var(--ink3); margin-bottom: 0.3rem; }
.chk .ov { background: color-mix(in srgb, var(--flag) 20%, transparent); }
.chk.cut .m { color: var(--stop); }

/* metric readout */
.mets { display: flex; flex-wrap: wrap; gap: 1.6rem; margin-bottom: 1.1rem; }
.met .k { font: 400 0.62rem/1 var(--mono); letter-spacing: 0.14em; text-transform: uppercase; color: var(--ink3); }
.met .v { font: 400 1.55rem/1.25 var(--mono); font-variant-numeric: tabular-nums; }
.met .v.hi { color: var(--live); }
.met .v.mid { color: var(--flag); }
.met .v.lo { color: var(--stop); }

.picks { margin-bottom: 1rem; }
.pick { display: flex; align-items: center; gap: 0.6rem; padding: 0.28rem 0; border-bottom: 1px solid var(--rule); font-size: 0.9rem; cursor: pointer; }
.pick:last-child { border-bottom: none; }
.pick .rk { font: 400 0.7rem/1 var(--mono); color: var(--ink3); width: 1.5rem; }
.pick input { accent-color: var(--live); }
.pick.on { color: var(--live); }

/* quiz */
.quiz { margin: 2.4rem 0; border-top: 1px solid var(--ink); padding-top: 0.7rem; }
.quiz > .head .l { font: 400 0.62rem/1 var(--mono); letter-spacing: 0.19em; text-transform: uppercase; color: var(--live); }
.quiz > .head h4 { margin: 0.25rem 0 1rem; font-size: 1rem; font-weight: 600; }
.q { margin-bottom: 1.6rem; }
.q:last-child { margin-bottom: 0; }
.q .stem { font-size: 0.98rem; margin-bottom: 0.7rem; }
.opt {
  display: block; width: 100%; text-align: left;
  background: none; border: none;
  border-bottom: 1px solid var(--rule);
  color: var(--ink2);
  font: 400 0.92rem/1.5 var(--serif);
  padding: 0.42rem 0 0.42rem 1.6rem;
  cursor: pointer; position: relative;
  transition: color 0.15s, background 0.15s;
}
.opt::before {
  content: attr(data-key);
  position: absolute; left: 0; top: 0.5rem;
  font: 400 0.68rem/1 var(--mono);
  color: var(--ink3);
}
.opt:hover:not([disabled]) { color: var(--ink); }
.opt.right { color: var(--live); }
.opt.right::before { content: "\2713"; color: var(--live); }
.opt.wrong { color: var(--stop); text-decoration: line-through; text-decoration-thickness: 1px; }
.opt.wrong::before { content: "\00d7"; color: var(--stop); }
.opt[disabled] { cursor: default; }
.expl {
  display: none;
  font-size: 0.9rem; color: var(--ink2);
  margin-top: 0.7rem; padding-left: 1.15rem;
  border-left: 2px solid var(--rule2);
}
.expl.show { display: block; animation: fade 0.25s ease; }
@keyframes fade { from { opacity: 0; transform: translateY(-2px); } to { opacity: 1; transform: none; } }

/* diagrams */
.fig { margin: 1.6rem 0; }
.fig pre { background: none; border-left: none; padding: 0; font-size: 0.74rem; line-height: 1.7; color: var(--ink2); }
.fig figcaption { font: 400 0.66rem/1.5 var(--mono); letter-spacing: 0.13em; text-transform: uppercase; color: var(--ink3); margin-top: 0.5rem; }

/* misc */
details { border-top: 1px solid var(--rule); padding: 0.7rem 0; margin-bottom: 0.4rem; }
summary { cursor: pointer; font-weight: 600; font-size: 0.95rem; list-style: none; position: relative; padding-left: 1.1rem; }
summary::-webkit-details-marker { display: none; }
summary::before { content: "+"; position: absolute; left: 0; font-family: var(--mono); color: var(--accent); }
details[open] summary::before { content: "\2212"; }
details[open] summary { margin-bottom: 0.8rem; }

.donebox {
  margin-top: 3.2rem; padding-top: 1.2rem;
  border-top: 1px solid var(--rule);
  display: flex; align-items: center; gap: 0.6rem;
}
.donebox label { display: flex; align-items: center; gap: 0.6rem; cursor: pointer; font: 400 0.72rem/1 var(--mono); letter-spacing: 0.13em; text-transform: uppercase; color: var(--ink3); transition: color 0.15s; }
.donebox label:hover { color: var(--ink); }
.donebox input { accent-color: var(--live); width: 0.95rem; height: 0.95rem; }

.pager { display: flex; justify-content: space-between; gap: 1.5rem; margin-top: 2.4rem; }
.pager a { border: none; font-size: 0.94rem; max-width: 46%; }
.pager a .d { display: block; font: 400 0.62rem/1.6 var(--mono); letter-spacing: 0.16em; text-transform: uppercase; color: var(--ink3); }
.pager a:last-child { text-align: right; }

.toc { list-style: none; padding: 0; margin: 0 0 1.5rem; }
.toc li { border-bottom: 1px solid var(--rule); margin: 0; padding: 0; }
.toc a { display: grid; grid-template-columns: 2.4rem 1fr; gap: 0.5rem; padding: 0.62rem 0; border: none; color: var(--ink); align-items: baseline; }
.toc a:hover { color: var(--accent); }
.toc a .n { font: 400 0.7rem/1 var(--mono); color: var(--ink3); }
.toc a .t { font-size: 1rem; }
.toc a .s { display: block; font-size: 0.85rem; color: var(--ink3); margin-top: 0.1rem; }

.kv { margin: 0 0 1.3rem; }
.kv div { display: grid; grid-template-columns: 8.5rem 1fr; gap: 0.8rem; padding: 0.3rem 0; border-bottom: 1px solid var(--rule); font-size: 0.92rem; }
.kv div:last-child { border-bottom: none; }
.kv dt { font: 400 0.66rem/1.55 var(--mono); letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink3); }
.kv dd { margin: 0; }

.small { font-size: 0.86rem; color: var(--ink2); }
.mono { font-family: var(--mono); font-size: 0.85em; }
.ok { color: var(--live); }
.no { color: var(--stop); }

@media (max-width: 62rem) {
  article { margin-left: 0; padding: 2.2rem 1.4rem 5rem; }
  h3 .sn { position: static; display: block; margin-bottom: 0.2rem; }
  #topbar { padding: 1rem 1.4rem; }
  #sidebar {
    position: fixed; left: 0; top: 0; z-index: 60;
    background: var(--paper);
    transform: translateX(-100%);
    transition: transform 0.25s cubic-bezier(.2,.7,.3,1);
  }
  #sidebar.open { transform: none; }
  #menubtn { display: inline; }
}

@media print {
  #sidebar, #topbar, .pager, .donebox, .quiz { display: none; }
  article { margin: 0; max-width: none; }
  section.module[hidden] { display: block !important; }
}

/* ---------- journal index ---------- */
.entries { list-style: none; padding: 0; margin: 2rem 0 0; }
.entries li { border-top: 1px solid var(--rule); margin: 0; padding: 0; }
.entries li:last-child { border-bottom: 1px solid var(--rule); }
.entry {
  display: block; padding: 1.4rem 0; border: none; text-decoration: none;
  color: inherit; width: 100%;
}
.entry .meta {
  font: 400 0.64rem/1 var(--mono);
  letter-spacing: 0.16em; text-transform: uppercase; color: var(--ink3);
  margin-bottom: 0.5rem; display: flex; gap: 0.9rem; align-items: baseline;
}
.entry .kind { color: var(--accent); }
.entry h3 {
  margin: 0 0 0.35rem; font: 400 1.32rem/1.25 var(--serif);
  letter-spacing: -0.015em; color: var(--ink); transition: color 0.15s;
}
.entry:hover h3 { color: var(--accent); }
.entry p { margin: 0; color: var(--ink2); font-size: 0.98rem; }

/* the index has no sidebar, so centre the column */
article.plain { margin-left: auto; margin-right: auto; }