/* xper — project site
   Terminal × lab-notebook. Light and dark, both first-class. */

/* ---------- tokens ---------- */
:root {
  --paper:        #FBFAF7;
  --raised:       #FFFFFF;
  --ink:          #15181B;
  --ink-soft:     #525C66;
  --ink-faint:    #8B949D;
  --rule:         #DFDACF;
  --rule-soft:    #EDE9E1;
  --accent:       #0B6E4F;
  --accent-wash:  rgba(11, 110, 79, 0.09);
  --secondary:    #2D5FA8;
  --sec-wash:     rgba(45, 95, 168, 0.09);
  --code-bg:      #F4F2EB;
  --grid:         rgba(21, 24, 27, 0.045);
  --shadow:       0 1px 2px rgba(21, 24, 27, .05), 0 6px 20px -12px rgba(21, 24, 27, .18);

  --mono: "IBM Plex Mono", ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
  --sans: "IBM Plex Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;

  --measure: 68ch;
  --page: 1080px;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper:       #0E1114;
    --raised:      #141A21;
    --ink:         #D6DBE0;
    --ink-soft:    #99A4AF;
    --ink-faint:   #667079;
    --rule:        #242C34;
    --rule-soft:   #1B222A;
    --accent:      #3FBF8F;
    --accent-wash: rgba(63, 191, 143, 0.11);
    --secondary:   #6C9BE0;
    --sec-wash:    rgba(108, 155, 224, 0.11);
    --code-bg:     #151C23;
    --grid:        rgba(255, 255, 255, 0.032);
    --shadow:      0 1px 2px rgba(0,0,0,.3), 0 6px 20px -12px rgba(0,0,0,.7);
    color-scheme: dark;
  }
}

:root[data-theme="dark"] {
  --paper:       #0E1114;
  --raised:      #141A21;
  --ink:         #D6DBE0;
  --ink-soft:    #99A4AF;
  --ink-faint:   #667079;
  --rule:        #242C34;
  --rule-soft:   #1B222A;
  --accent:      #3FBF8F;
  --accent-wash: rgba(63, 191, 143, 0.11);
  --secondary:   #6C9BE0;
  --sec-wash:    rgba(108, 155, 224, 0.11);
  --code-bg:     #151C23;
  --grid:        rgba(255, 255, 255, 0.032);
  --shadow:      0 1px 2px rgba(0,0,0,.3), 0 6px 20px -12px rgba(0,0,0,.7);
  color-scheme: dark;
}

/* ---------- base ---------- */
*, *::before, *::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }

body {
  margin: 0;
  font-family: var(--sans);
  font-size: 16.5px;
  line-height: 1.65;
  color: var(--ink);
  background-color: var(--paper);
  /* graph paper */
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 28px 28px;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration-thickness: 1px; text-underline-offset: 2px; }
a:hover { text-decoration-thickness: 2px; }

h1, h2, h3 { line-height: 1.2; letter-spacing: -0.015em; font-weight: 600; }

code, kbd, pre { font-family: var(--mono); }

/* grid children must be allowed to shrink below their min-content width,
   otherwise a long unbreakable line (a clone URL) widens the whole page
   instead of scrolling inside its own .code block */
.install-grid > *, .feats > *, .cards > *, .tree-grid > * { min-width: 0; }

/* ---------- layout ---------- */
.wrap { width: 100%; max-width: var(--page); margin: 0 auto; padding: 0 28px; }
.narrow { max-width: var(--measure); }

section { padding: 76px 0; border-top: 1px solid var(--rule-soft); }
section:first-of-type { border-top: 0; }

/* section numbering, lab-report style */
.sec-label {
  font-family: var(--mono);
  font-size: 11.5px;
  font-weight: 500;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin: 0 0 10px;
  display: flex;
  align-items: center;
  gap: 12px;
}
.sec-label::after {
  content: "";
  flex: 1;
  height: 1px;
  background: var(--rule);
}
h2.sec-title { font-size: clamp(24px, 3.4vw, 32px); margin: 0 0 14px; }
.sec-lede { color: var(--ink-soft); max-width: var(--measure); margin: 0 0 34px; }

/* ---------- header ---------- */
header.top {
  position: sticky; top: 0; z-index: 40;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--rule-soft);
}
.top-in { display: flex; align-items: center; gap: 18px; height: 56px; }
.brand {
  font-family: var(--mono); font-weight: 600; font-size: 17px;
  color: var(--ink); text-decoration: none; letter-spacing: -0.02em;
}
.brand::before { content: "$ "; color: var(--accent); }
.top-nav { margin-left: auto; display: flex; align-items: center; gap: 20px; }
.top-nav a {
  font-size: 14px; color: var(--ink-soft); text-decoration: none;
}
.top-nav a:hover { color: var(--ink); }
@media (max-width: 700px) { .top-nav a.hide-sm { display: none; } }

.theme-btn {
  display: grid; place-items: center;
  width: 32px; height: 32px; padding: 0;
  border: 1px solid var(--rule); border-radius: 7px;
  background: var(--raised); color: var(--ink-soft);
  cursor: pointer;
}
.theme-btn:hover { color: var(--ink); border-color: var(--ink-faint); }
.theme-btn svg { width: 15px; height: 15px; }
:root[data-theme="dark"] .icon-sun, .icon-moon { display: none; }
:root[data-theme="dark"] .icon-moon { display: block; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .icon-sun { display: none; }
  :root:not([data-theme="light"]) .icon-moon { display: block; }
  :root[data-theme="light"] .icon-sun { display: block; }
}

/* ---------- hero ---------- */
.hero { padding: 84px 0 68px; border-top: 0; }
.hero h1 {
  font-family: var(--mono);
  font-size: clamp(46px, 9vw, 78px);
  font-weight: 600;
  letter-spacing: -0.045em;
  margin: 0 0 4px;
}
.hero h1 .cursor {
  display: inline-block; width: .5em; height: .82em;
  background: var(--accent); vertical-align: -0.06em; margin-left: .1em;
  animation: blink 1.15s steps(1) infinite;
}
@keyframes blink { 50% { opacity: 0; } }
@media (prefers-reduced-motion: reduce) { .hero h1 .cursor { animation: none; } }

.tagline {
  font-size: clamp(19px, 2.6vw, 25px);
  line-height: 1.35;
  color: var(--ink);
  margin: 0 0 16px;
  max-width: 22ch;
  font-weight: 400;
}
.tagline em { font-style: normal; color: var(--accent); }
.hero-sub { color: var(--ink-soft); max-width: 54ch; margin: 0 0 30px; }
.hero-sub strong { font-weight: 600; color: var(--ink); }

.btn-row { display: flex; flex-wrap: wrap; gap: 12px; margin-bottom: 34px; }
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  font-family: var(--mono); font-size: 14px; font-weight: 500;
  padding: 9px 17px; border-radius: 8px;
  text-decoration: none; border: 1px solid transparent; cursor: pointer;
}
.btn-primary { background: var(--ink); color: var(--paper); }
.btn-primary:hover { opacity: .87; }
.btn-ghost { border-color: var(--rule); color: var(--ink); background: var(--raised); }
.btn-ghost:hover { border-color: var(--ink-faint); }
.btn svg { width: 15px; height: 15px; }

/* ---------- code blocks ---------- */
.code {
  position: relative;
  background: var(--code-bg);
  border: 1px solid var(--rule);
  border-radius: 10px;
  font-family: var(--mono);
  font-size: 13.5px;
  line-height: 1.75;
  overflow-x: auto;
}
.code pre { margin: 0; padding: 16px 18px; }
.code.with-copy pre { padding-right: 74px; }
.code .c-prompt { color: var(--accent); user-select: none; }
.code .c-cmt    { color: var(--ink-faint); }
.code .c-flag   { color: var(--secondary); }
.code .c-str    { color: var(--ink); }

.copy {
  position: absolute; top: 9px; right: 9px;
  font-family: var(--mono); font-size: 11px; letter-spacing: .04em;
  padding: 5px 9px; border-radius: 6px;
  border: 1px solid var(--rule); background: var(--raised); color: var(--ink-soft);
  cursor: pointer;
}
.copy:hover { color: var(--ink); border-color: var(--ink-faint); }
.copy.done { color: var(--accent); border-color: var(--accent); }

/* ---------- figure convention ---------- */
figure.fig { margin: 0; }
figcaption.fig-cap {
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: 0.07em;
  color: var(--ink-faint);
  margin-top: 14px;
  text-align: center;
}
figcaption.fig-cap b {
  color: var(--ink-soft); font-weight: 500; text-transform: uppercase;
}

/* ---------- problem note ---------- */
.note {
  border-left: 2px solid var(--accent);
  background: var(--accent-wash);
  padding: 20px 24px;
  border-radius: 0 10px 10px 0;
  max-width: var(--measure);
}
.note p { margin: 0 0 12px; }
.note p:last-child { margin: 0; }
.note .kicker {
  font-family: var(--mono); font-size: 11.5px; letter-spacing: .1em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 8px;
}

/* ---------- the tree ---------- */
.tree-grid {
  display: grid;
  grid-template-columns: minmax(300px, 400px) 1fr;
  gap: 34px;
  align-items: start;
  background: var(--raised);
  border: 1px solid var(--rule);
  border-radius: 12px;
  padding: 24px;
  box-shadow: var(--shadow);
}
@media (max-width: 1000px) { .tree-grid { grid-template-columns: 1fr; gap: 22px; } }

.steps { list-style: none; margin: 0; padding: 0; font-family: var(--mono); font-size: 13px; }
.steps li {
  display: block; width: 100%; text-align: left;
  padding: 6px 10px; border-radius: 7px; cursor: pointer;
  color: var(--ink-faint); border: 0; background: none;
  font: inherit; line-height: 1.5;
  transition: background .15s, color .15s;
}
.steps li:hover { background: var(--rule-soft); }
.steps li .s-cmd::before { content: "$ "; color: var(--ink-faint); }
.steps li.is-edit .s-cmd::before { content: "# "; }
.steps li .s-note { color: var(--ink-faint); font-size: 12px; }
.steps li .s-note::before { content: " — "; }
.steps li[data-done] { color: var(--ink-soft); }
.steps li[data-done] .s-cmd::before { color: var(--accent); }
.steps li[data-current] {
  background: var(--accent-wash);
  color: var(--ink);
}
.steps li[data-current] .s-cmd { font-weight: 600; }
.steps li.is-edit { font-style: italic; }

.tree-stage { min-width: 0; }
.tree-scroll { overflow-x: auto; }
.tree-svg { display: block; width: 100%; min-width: 430px; height: auto; }

.tree-svg .edge {
  fill: none; stroke: var(--rule); stroke-width: 2; stroke-linecap: round;
  opacity: 0; transition: opacity .45s ease, stroke .3s;
}
.tree-svg .edge.scratch { stroke-dasharray: 3 5; }
.tree-svg .node { opacity: 0; transition: opacity .35s ease; }
.tree-svg [data-on="1"] { opacity: 1; }
.tree-svg .node circle {
  fill: var(--raised); stroke: var(--ink-faint); stroke-width: 2;
  transition: fill .25s, stroke .25s, r .25s;
}
.tree-svg .node text {
  font-family: var(--mono); font-size: 13px; font-weight: 500;
  fill: var(--ink-soft); text-anchor: middle;
  transition: fill .25s;
}
.tree-svg .node .n-tag {
  font-size: 10.5px; font-weight: 500; fill: var(--ink-faint);
  letter-spacing: .06em;
}
.tree-svg .node[data-on="1"] circle { stroke: var(--accent); }
.tree-svg .node[data-on="1"] text { fill: var(--ink); }
.tree-svg .edge[data-on="1"] { stroke: var(--accent); opacity: .5; }
.tree-svg .node[data-active="1"] circle {
  fill: var(--accent); stroke: var(--accent); r: 8.5;
}
.tree-svg .node[data-active="1"] text { fill: var(--accent); font-weight: 600; }
.tree-svg .halo {
  fill: none; stroke: var(--accent); stroke-width: 2; opacity: 0;
  transition: opacity .3s;
}
.tree-svg .node[data-active="1"] .halo { opacity: .28; }

.tree-bar {
  display: flex; align-items: center; gap: 10px;
  margin-top: 14px; padding-top: 14px; border-top: 1px solid var(--rule-soft);
}
.tree-bar .replay {
  font-family: var(--mono); font-size: 12px;
  padding: 5px 12px; border-radius: 6px;
  border: 1px solid var(--rule); background: var(--paper); color: var(--ink-soft);
  cursor: pointer;
}
.tree-bar .replay:hover { color: var(--ink); border-color: var(--ink-faint); }
.tree-bar .hint { font-size: 12.5px; color: var(--ink-faint); margin-left: auto; }
@media (max-width: 520px) { .tree-bar .hint { display: none; } }

.takeaway {
  margin: 30px auto 0;
  max-width: 62ch; text-align: center;
  font-size: 18px; color: var(--ink-soft);
}
.takeaway b { color: var(--ink); font-weight: 600; }

/* ---------- comparison ---------- */
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(232px, 1fr)); gap: 16px; }
.card {
  background: var(--raised);
  border: 1px solid var(--rule);
  border-radius: 11px;
  padding: 20px;
}
.card h3 {
  font-family: var(--mono); font-size: 14px; margin: 0 0 4px;
  display: flex; align-items: center; gap: 8px;
}
.card .verdict {
  font-family: var(--mono); font-size: 10.5px; letter-spacing: .08em;
  text-transform: uppercase; color: var(--ink-faint); margin-bottom: 12px;
}
.card p { margin: 0; font-size: 14.5px; color: var(--ink-soft); line-height: 1.6; }
.card.is-xper { border-color: var(--accent); background: var(--accent-wash); }
.card.is-xper h3 { color: var(--accent); }
.card.is-xper .verdict { color: var(--accent); }
.card.is-xper p { color: var(--ink); }

/* ---------- features ---------- */
.feats { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 22px; }
.feat {
  border: 1px solid var(--rule); border-radius: 11px;
  background: var(--raised); padding: 22px; display: flex; flex-direction: column;
}
.feat h3 { font-size: 17px; margin: 0 0 8px; }
.feat > p { margin: 0 0 16px; font-size: 14.5px; color: var(--ink-soft); flex: 1; }
.feat .code { font-size: 12.5px; }

/* ---------- demos ---------- */
.demo { margin-bottom: 34px; }
.demo:last-child { margin-bottom: 0; }
.demo h3 { font-size: 16px; margin: 0 0 4px; }
.demo .demo-sub { font-size: 14px; color: var(--ink-soft); margin: 0 0 14px; }
.demo-frame {
  border: 1px solid var(--rule); border-radius: 11px;
  overflow: hidden; background: var(--code-bg);
}
.demo-fallback { margin: 0; }
.demo-fallback .code { border: 0; border-radius: 0; background: transparent; }
.demo-pending {
  display: flex; align-items: center; gap: 9px;
  padding: 10px 18px; border-top: 1px dashed var(--rule);
  font-family: var(--mono); font-size: 11.5px; color: var(--ink-faint);
}
.demo-pending::before {
  content: ""; width: 6px; height: 6px; border-radius: 50%;
  background: var(--ink-faint); flex: none;
}

/* ---------- reference table ---------- */
.ref-scroll { overflow-x: auto; border: 1px solid var(--rule); border-radius: 11px; background: var(--raised); }
table.ref { border-collapse: collapse; width: 100%; min-width: 640px; font-size: 14px; }
table.ref th, table.ref td { text-align: left; padding: 11px 18px; vertical-align: top; }
table.ref thead th {
  font-family: var(--mono); font-size: 11px; letter-spacing: .1em; text-transform: uppercase;
  color: var(--ink-faint); font-weight: 500; border-bottom: 1px solid var(--rule);
}
table.ref tbody tr { border-bottom: 1px solid var(--rule-soft); }
table.ref tbody tr:last-child { border-bottom: 0; }
table.ref td:first-child { white-space: nowrap; }
table.ref td code {
  font-size: 13px; color: var(--ink);
  background: var(--code-bg); border: 1px solid var(--rule-soft);
  padding: 2px 6px; border-radius: 5px;
}
table.ref td code .c-flag { color: var(--secondary); }
table.ref td:last-child { color: var(--ink-soft); }
table.ref tr.group td {
  background: var(--code-bg);
  font-family: var(--mono); font-size: 11px; letter-spacing: .12em;
  text-transform: uppercase; color: var(--ink-soft); font-weight: 500;
  padding: 8px 18px;
}

.gotchas { margin-top: 26px; }
.gotchas h3 { font-size: 15px; margin: 0 0 12px; font-family: var(--mono); }
.gotchas ul { margin: 0; padding-left: 20px; color: var(--ink-soft); font-size: 14.5px; }
.gotchas li { margin-bottom: 9px; }
.gotchas li:last-child { margin-bottom: 0; }
.gotchas code {
  font-size: 13px; background: var(--code-bg);
  border: 1px solid var(--rule-soft); padding: 1px 5px; border-radius: 4px; color: var(--ink);
}

/* ---------- install ---------- */
.install-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 22px; align-items: start; }
@media (max-width: 780px) { .install-grid { grid-template-columns: 1fr; } }
.install-grid h3 { font-size: 15px; margin: 0 0 10px; font-family: var(--mono); }
.install-grid p { font-size: 14.5px; color: var(--ink-soft); margin: 10px 0 0; }

/* ---------- footer ---------- */
footer {
  border-top: 1px solid var(--rule);
  padding: 40px 0 56px;
  font-size: 14px; color: var(--ink-soft);
}
.foot-in { display: flex; flex-wrap: wrap; gap: 16px 28px; align-items: center; }
.foot-in .foot-brand { font-family: var(--mono); font-weight: 600; color: var(--ink); }
.foot-in .spacer { flex: 1; }
footer a { color: var(--ink-soft); }
footer a:hover { color: var(--accent); }

/* ---------- mode switch (section 02) ---------- */
.mode-switch {
  display: inline-flex; gap: 4px; margin-bottom: 28px;
  padding: 4px; border: 1px solid var(--rule); border-radius: 10px;
  background: var(--code-bg);
}
.mode-switch button {
  font-family: var(--mono); font-size: 13px; font-weight: 500;
  padding: 7px 15px; border-radius: 7px; cursor: pointer;
  border: 1px solid transparent; background: none; color: var(--ink-soft);
}
.mode-switch button:hover { color: var(--ink); }
.mode-switch button[aria-pressed="true"] {
  background: var(--raised); border-color: var(--rule);
  color: var(--ink); box-shadow: var(--shadow);
}
.mode-panel h3 { font-size: 20px; margin: 0 0 8px; }
.mode-panel > p.mode-lede { color: var(--ink-soft); max-width: var(--measure); margin: 0 0 26px; }

/* ---------- supervisional figure ---------- */
.seq-wrap {
  background: var(--raised); border: 1px solid var(--rule);
  border-radius: 12px; padding: 22px; box-shadow: var(--shadow);
}
.keybar {
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  padding: 11px 15px; margin-bottom: 18px;
  border: 1px solid var(--rule); border-radius: 9px; background: var(--code-bg);
  font-family: var(--mono); font-size: 12.5px;
}
.keybar .kb-branch { color: var(--ink); font-weight: 600; }
.keybar .kb-mode {
  font-size: 10.5px; letter-spacing: .09em; text-transform: uppercase;
  color: var(--secondary); border: 1px solid var(--secondary);
  border-radius: 20px; padding: 2px 9px;
}
.keybar .kb-key { margin-left: auto; display: flex; align-items: center; gap: 7px; color: var(--ink-soft); }
.keybar .kb-holder {
  font-weight: 600; padding: 2px 10px; border-radius: 20px;
  border: 1px solid var(--rule); background: var(--raised); color: var(--ink-faint);
  transition: color .25s, border-color .25s, background .25s;
}
.keybar .kb-holder[data-held="1"] { color: var(--accent); border-color: var(--accent); background: var(--accent-wash); }
.keybar svg { width: 14px; height: 14px; flex: none; color: var(--ink-faint); }
.keybar[data-held="1"] svg { color: var(--accent); }

.lanes { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
@media (max-width: 720px) { .lanes { grid-template-columns: 1fr; } }

.lane { border: 1px solid var(--rule); border-radius: 10px; overflow: hidden; background: var(--code-bg); }
.lane[data-absent="1"] { opacity: .42; }
.lane-head {
  display: flex; align-items: center; gap: 9px;
  padding: 9px 13px; border-bottom: 1px solid var(--rule);
  background: var(--raised); font-family: var(--mono); font-size: 12.5px;
}
.lane-head .who { font-weight: 600; color: var(--ink); }
.lane-head .badge {
  margin-left: auto; display: inline-flex; align-items: center; gap: 5px;
  font-size: 10.5px; letter-spacing: .07em; text-transform: uppercase;
  padding: 2px 9px; border-radius: 20px; border: 1px solid var(--rule); color: var(--ink-faint);
  transition: color .25s, border-color .25s;
}
.lane-head .badge svg { width: 11px; height: 11px; }
.lane[data-lock="open"] .badge { color: var(--accent); border-color: var(--accent); }
.lane[data-lock="lock"] .badge { color: var(--ink-faint); }
.lane-head .badge .lbl-open { display: none; }
.lane[data-lock="open"] .badge .lbl-open { display: inline; }
.lane[data-lock="open"] .badge .lbl-lock { display: none; }

.lane-body { padding: 11px 13px; font-family: var(--mono); font-size: 12.5px; min-height: 210px; }
.lane-body .line {
  display: block; padding: 3px 0; color: var(--ink-faint);
  opacity: 0; transform: translateY(-2px);
  transition: opacity .3s, color .3s, transform .3s;
}
.lane-body .line[data-on="1"] { opacity: 1; transform: none; color: var(--ink-soft); }
.lane-body .line .lc::before { content: "$ "; color: var(--ink-faint); }
.lane-body .line[data-current="1"] { color: var(--ink); }
.lane-body .line[data-current="1"] .lc { font-weight: 600; }
.lane-body .line[data-current="1"] .lc::before { color: var(--accent); }
.lane-body .line .ln { display: block; padding-left: 14px; font-size: 11.5px; color: var(--ink-faint); }
.lane-body .line.denied .lc { color: var(--ink-faint); text-decoration: line-through; text-decoration-thickness: 1px; }
.lane-body .line.denied .lc::before { content: "⨯ "; color: #c0563f; text-decoration: none; }
:root[data-theme="dark"] .lane-body .line.denied .lc::before { color: #e0806a; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .lane-body .line.denied .lc::before { color: #e0806a; }
}