/* ══════════════════════════════════════════════════════════════
   PPG — styled to the Camora design system.

   Token names and values are Camora's own (apps/camora/src/styles/
   globals.css), so this app reads as part of the product rather than
   beside it. The ramp used is the Lumora shell's — the surface the
   playground actually lives on — which is why the sans face is Open
   Sans and not the Segoe UI that Capra keeps.

   Dark is the default; [data-theme="light"] overrides, matching
   Camora's own dark-first structure.
   ══════════════════════════════════════════════════════════════ */

:root {
  /* ── ground and surfaces ──
     Three stacked planes rather than one flat fill. Each step up is lighter and
     very slightly cooler, which is what lets a card read as raised without a
     heavy border doing the work. */
  --ground:     #050B0E;
  --surface-1:  #0A1014;
  --surface-2:  #0F181D;
  --surface-3:  #16222A;

  --bg-base:      var(--ground);
  --bg-app:       var(--surface-1);
  --bg-surface:   var(--surface-1);
  --bg-elevated:  var(--surface-2);
  --bg-raised:    var(--surface-3);
  --bg-overlay:   rgba(2,6,8,.74);

  /* Alpha borders sit correctly on every plane; a fixed hex only suits one. */
  --border:        rgba(190,235,245,.075);
  --border-strong: rgba(190,235,245,.13);
  --border-hover:  rgba(190,235,245,.2);
  --hairline:      rgba(190,235,245,.055);
  --inset-top:     rgba(210,245,255,.06);

  --text-primary:   #E9F0F2;
  --text-secondary: #9FB2B9;
  --text-muted:     #8AA1AA;
  --text-dimmed:    #76909A;   /* 5.68:1 on --surface-1 */

  --accent:         #F5A524;
  --accent-hover:   #FFC152;
  --accent-text:    #FFC152;
  --accent-subtle:  rgba(245,165,36,.12);
  --accent-line:    rgba(245,165,36,.36);
  --accent-glow:    rgba(245,165,36,.28);
  --accent-ink:     #1A1203;

  --success: #35D6A4;
  --warning: #E8C34A;
  --danger:  #FF6B84;

  --easy:   #35D6A4;
  --medium: #E8C34A;
  --hard:   #FF6B84;

  --rail-head:      #5FE3B8;            /* 10.4:1 on --surface-1 */
  --rail-head-mark: rgba(95,227,184,.9);
  --rail-head-line: rgba(95,227,184,.16);

  --syn-keyword: #FFB37C;
  --syn-string:  #7EE3C1;
  --syn-number:  #F5CB5C;
  --syn-comment: #6B858F;
  --syn-def:     #7FD3F7;
  --syn-builtin: #C9A5F0;
  --syn-operator:#9FB2B9;

  /* ── type ── Geist is a contemporary product face; Geist Mono its companion. */
  --font-sans: 'Geist', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'Geist Mono', ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --fs-body-s:     12px;  --lh-body-s:     16px;
  --fs-body-m:     13.5px; --lh-body-m:    20px;
  --fs-heading-xs: 14px;  --lh-heading-xs: 18px;
  --fs-heading-s:  15px;  --lh-heading-s:  22px;
  --fs-heading-m:  18px;  --lh-heading-m:  24px;
  --fs-heading-l:  21px;  --lh-heading-l:  28px;
  --fs-heading-xl: 26px;  --lh-heading-xl: 32px;

  --radius-card:    14px;
  --radius-card-sm: 10px;
  --radius-chip:    9999px;
  --radius-badge:    6px;
  --radius-input:    9px;

  /* Shadows carry a trace of the accent hue instead of neutral black. */
  --shadow-xs: 0 1px 2px rgba(4,5,10,.5);
  --shadow-sm: 0 1px 2px rgba(4,5,10,.4), 0 3px 10px rgba(4,5,10,.35);
  --shadow-md: 0 2px 6px rgba(2,6,8,.5), 0 14px 36px rgba(0,4,6,.55);
  --shadow-focus: 0 0 0 3px var(--accent-glow);

  --ease: cubic-bezier(.22,.61,.36,1);
  --dur: 140ms;

  --edge:     rgba(190,225,240,.42);
  --edge-dot: rgba(190,225,240,.62);
  --rail: 268px;
  --probw: minmax(320px, 0.92fr);
}

[data-theme="light"] {
  --ground:     #FBFAF7;
  --surface-1:  #FFFFFF;
  --surface-2:  #F5F3EE;
  --surface-3:  #EDEAE3;

  --bg-base:      var(--ground);
  --bg-app:       var(--surface-1);
  --bg-surface:   var(--surface-1);
  --bg-elevated:  var(--surface-2);
  --bg-raised:    var(--surface-3);
  --bg-overlay:   rgba(16,18,26,.30);

  --border:        rgba(20,26,28,.10);
  --border-strong: rgba(20,26,28,.15);
  --border-hover:  rgba(20,26,28,.24);
  --hairline:      rgba(20,26,28,.075);
  --inset-top:     rgba(255,255,255,.9);

  --text-primary:   #101619;
  --text-secondary: #4C5A60;
  --text-muted:     #5B6A70;
  --text-dimmed:    #66757C;   /* 4.77:1 on white */

  --accent:         #9A5B07;
  --accent-hover:   #7D4A05;
  --accent-text:    #9A5B07;
  --accent-subtle:  rgba(154,91,7,.10);
  --accent-line:    rgba(154,91,7,.30);
  --accent-glow:    rgba(154,91,7,.22);
  --accent-ink:     #FFFFFF;

  --success: #0B7A5C;
  --warning: #8A6300;
  --danger:  #C42B47;

  --easy:   #0B7A5C;
  --medium: #8A6300;
  --hard:   #C42B47;

  --rail-head:      #0A6B50;            /* 5.9:1 on white */
  --rail-head-mark: rgba(10,107,80,.85);
  --rail-head-line: rgba(10,107,80,.16);

  --syn-keyword: #9A4B18;
  --syn-string:  #0A6B52;
  --syn-number:  #8A5A00;
  --syn-comment: #63737B;
  --syn-def:     #15608F;
  --syn-builtin: #6A3FB5;
  --syn-operator:#535A6B;

  --shadow-xs: 0 1px 1px rgba(16,18,26,.05);
  --shadow-sm: 0 1px 2px rgba(16,18,26,.06), 0 3px 10px rgba(16,18,26,.05);
  --shadow-md: 0 2px 6px rgba(16,18,26,.07), 0 12px 28px rgba(16,18,26,.09);
  --edge:     rgba(20,26,28,.34);
  --edge-dot: rgba(20,26,28,.5);
}

* { box-sizing: border-box; }
/* An author `display` beats the UA stylesheet, so a flex button carrying the
   `hidden` attribute would still paint. This keeps `hidden` meaning hidden. */
[hidden] { display: none !important; }
html, body { height: 100%; }
body {
  margin: 0;
  color: var(--text-primary);
  font: var(--fs-body-m)/var(--lh-body-m) var(--font-sans);
  overflow: hidden;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  letter-spacing: -0.005em;
  /* A flat fill is what reads as dated. Two very low-opacity pools give the
     shell depth without becoming decoration. */
  background:
    radial-gradient(1100px 620px at 12% -8%,  var(--accent-subtle), transparent 62%),
    radial-gradient(950px 540px at 104% 2%, color-mix(in oklab, var(--success) 8%, transparent), transparent 60%),
    var(--bg-base);
  background-attachment: fixed;
}
button { font: inherit; color: inherit; }
:focus-visible { outline: none; box-shadow: var(--shadow-focus); border-radius: var(--radius-badge); }
::selection { background: var(--accent-subtle); }

::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 6px; border: 2px solid var(--bg-base); }
::-webkit-scrollbar-thumb:hover { background: var(--border-hover); }

/* ── top bar ─────────────────────────────────────────────── */
.topbar {
  height: 48px; flex: 0 0 48px;
  display: flex; align-items: center; gap: 18px; padding: 0 16px;
  background: color-mix(in oklab, var(--surface-1) 76%, transparent);
  backdrop-filter: blur(18px) saturate(150%);
  -webkit-backdrop-filter: blur(18px) saturate(150%);
  border-bottom: 1px solid var(--border);
  position: relative; z-index: 20;
}
.brand { display: flex; align-items: baseline; gap: 8px; }
.brand-mark { color: var(--accent); font-family: var(--font-mono); font-weight: 700; }
.brand-name { font-weight: 700; letter-spacing: .4px; font-size: var(--fs-heading-s); }
.brand-sub { color: var(--text-dimmed); font-size: var(--fs-body-s); }

.pg-tabs { display: flex; gap: 4px; margin-left: 6px; }
.pg-tab {
  padding: 5px 13px; border-radius: var(--radius-chip);
  border: 1px solid transparent; background: transparent;
  color: var(--text-secondary); cursor: pointer;
  font-size: var(--fs-body-m); display: flex; align-items: center; gap: 6px;
  transition: background .12s, color .12s, border-color .12s;
}
.pg-tab:hover { background: var(--bg-elevated); color: var(--text-primary); }
.pg-tab.is-on {
  background: var(--accent-subtle); color: var(--accent-text);
  border-color: var(--accent);
}
.pg-tab[disabled] { opacity: .45; cursor: not-allowed; }
.pg-tab .soon {
  font-size: 10px; background: var(--bg-elevated); border: 1px solid var(--border);
  padding: 1px 5px; border-radius: var(--radius-badge); color: var(--text-dimmed);
  text-transform: uppercase; letter-spacing: .06em;
}

.topbar-right { margin-left: auto; display: flex; align-items: center; gap: 12px; }
.runtime-status { display: flex; align-items: center; }
.runtime-status .dot {
  width: 9px; height: 9px; border-radius: 50%; background: var(--text-dimmed);
  box-shadow: 0 0 0 3px color-mix(in oklab, currentColor 0%, transparent);
  transition: background var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}
.runtime-status[data-state="ready"] .dot { box-shadow: 0 0 0 3px color-mix(in oklab, var(--success) 18%, transparent); }
.runtime-status[data-state="busy"]  .dot { box-shadow: 0 0 0 3px color-mix(in oklab, var(--accent) 20%, transparent); }
.runtime-status[data-state="error"] .dot { box-shadow: 0 0 0 3px color-mix(in oklab, var(--danger) 20%, transparent); }

/* Visible only to assistive technology — the dot alone conveys nothing to a
   screen reader. */
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}
.runtime-status[data-state="boot"]  .dot { background: var(--warning); animation: pulse 1.1s infinite; }
.runtime-status[data-state="ready"] .dot { background: var(--success); }
.runtime-status[data-state="busy"]  .dot { background: var(--accent); animation: pulse .7s infinite; }
.runtime-status[data-state="error"] .dot { background: var(--danger); }
@keyframes pulse { 0%,100% { opacity: 1 } 50% { opacity: .25 } }

/* ── icons ───────────────────────────────────────────────── */
.ico { display: block; flex: 0 0 auto; }
.brand-mark { display: flex; align-items: center; color: var(--accent); }
.p-item .stat, .case .mark, .sol-caret { display: flex; align-items: center; justify-content: center; }

/* ── buttons ─────────────────────────────────────────────── */
.btn {
  display: inline-flex; align-items: center; gap: 7px;
  border: 1px solid var(--border); background: var(--bg-elevated); color: var(--text-primary);
  padding: 6px 13px; border-radius: var(--radius-input); cursor: pointer;
  font-size: var(--fs-body-m); font-weight: 600; white-space: nowrap;
  transition: background .12s, border-color .12s, transform .06s;
}
.btn:hover { background: var(--bg-surface); border-color: var(--border-hover); }
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.btn-sm { padding: 4px 10px; font-size: var(--fs-body-s); font-weight: 600; }
.btn-icon { padding: 6px; }
.btn-ghost { background: transparent; border-color: transparent; color: var(--text-secondary); font-weight: 400; }
.btn-ghost:hover { background: var(--bg-elevated); color: var(--text-primary); border-color: transparent; }
.btn-primary {
  background: linear-gradient(180deg, var(--accent-hover), var(--accent));
  border-color: transparent; color: var(--accent-ink);
  box-shadow: 0 1px 2px rgba(4,5,10,.35), 0 0 0 1px var(--accent-line) inset;
}
.btn-primary:hover { filter: brightness(1.07); box-shadow: var(--shadow-focus); }
.btn-secondary { border-color: var(--accent); color: var(--accent-text); background: transparent; }
.btn-secondary:hover { background: var(--accent-subtle); }
.btn-danger { background: var(--danger); border-color: var(--danger); color: #fff; }
[data-theme="light"] .btn-danger { color: #fff; }

/* ── layout ──────────────────────────────────────────────── */
.layout {
  height: calc(100vh - 48px);
  display: grid; grid-template-columns: var(--rail) 5px var(--probw) 5px 1.1fr;
}
.layout.rail-hidden { grid-template-columns: 0 0 var(--probw) 5px 1.1fr; }
.rail-grip, .col-grip { background: transparent; cursor: col-resize; position: relative; }
.rail-grip::after, .col-grip::after {
  content: ""; position: absolute; inset: 0 2px; background: var(--border); transition: background .15s;
}
.rail-grip:hover::after, .col-grip:hover::after,
.dragging .rail-grip::after, .dragging .col-grip::after { background: var(--accent); }
.row-grip { height: 5px; cursor: row-resize; position: relative; flex: 0 0 auto; }
.row-grip::after { content: ""; position: absolute; inset: 2px 0; background: var(--border); transition: background .15s; }
.row-grip:hover::after { background: var(--accent); }
body.dragging { user-select: none; cursor: col-resize; }

/* ── rail ────────────────────────────────────────────────── */
.rail { background: var(--bg-surface); border-right: 1px solid var(--border); display: flex; flex-direction: column; overflow: hidden; }
.rail-head {
  padding: 12px; border-bottom: 1px solid var(--border);
  display: flex; flex-direction: column; gap: 10px;
  background: linear-gradient(180deg, var(--bg-elevated), var(--bg-surface));
}

/* Progress summary: one ring for the whole catalogue, three meters for the split. */
.rail-stats { display: flex; align-items: center; gap: 12px; }
.ring {
  --pct: 0;
  position: relative; flex: 0 0 46px; width: 46px; height: 46px; border-radius: 50%;
  background: conic-gradient(var(--accent) calc(var(--pct) * 1%), var(--border) 0);
  display: grid; place-items: center;
}
.ring::after {
  content: ''; position: absolute; inset: 4px; border-radius: 50%;
  background: var(--bg-surface);
}
.ring-n {
  position: relative; z-index: 1; font: 700 13px/1 var(--font-mono);
  color: var(--text-primary); letter-spacing: -.02em;
}
.ring-n i { font-style: normal; font-size: 8.5px; color: var(--text-dimmed); margin-left: 1px; }
.rail-stats-b { flex: 1; min-width: 0; display: flex; flex-direction: column; gap: 5px; }
.rail-stats-h { margin: 0; font-size: 11.5px; color: var(--text-dimmed); }
.rail-stats-h b { color: var(--text-primary); font-size: 13px; font-family: var(--font-mono); }
.tiers { display: flex; flex-direction: column; gap: 3px; }
.tier { display: flex; align-items: center; gap: 6px; }
.tier-l { font: 700 9px/1 var(--font-mono); width: 7px; flex: none; }
.tier-bar {
  flex: 1; height: 3px; border-radius: 2px; background: var(--border); overflow: hidden;
}
.tier-bar i { display: block; height: 100%; border-radius: 2px; transition: width .35s var(--ease); }
.d-Easy-bg { background: var(--easy); }
.d-Medium-bg { background: var(--medium); }
.d-Hard-bg { background: var(--hard); }
.tier-n {
  font: 9.5px/1 var(--font-mono); color: var(--text-dimmed);
  width: 34px; text-align: right; flex: none; font-variant-numeric: tabular-nums;
}

/* Search with its own affordance rather than a bare box. */
.rail-search { position: relative; display: flex; align-items: center; }
.rail-search-i {
  position: absolute; left: 9px; display: flex; color: var(--text-dimmed); pointer-events: none;
}
.search {
  width: 100%; padding: 7px 34px 7px 29px; border-radius: var(--radius-input);
  border: 1px solid var(--border); background: var(--bg-base); color: var(--text-primary);
  font: var(--fs-body-m)/1.4 var(--font-sans); outline: none;
  transition: border-color var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}
.search::placeholder { color: var(--text-dimmed); }
.search:focus { border-color: var(--accent); box-shadow: var(--shadow-focus); }
.search::-webkit-search-cancel-button { -webkit-appearance: none; }
.rail-kbd {
  position: absolute; right: 8px; padding: 1px 5px; border-radius: 4px;
  border: 1px solid var(--border-strong); background: var(--bg-elevated);
  font: 10px/1.5 var(--font-mono); color: var(--text-dimmed); pointer-events: none;
}
.search:focus ~ .rail-kbd { opacity: 0; }

/* Segmented controls read as one object; loose chips read as four. */
.seg {
  display: grid; grid-auto-flow: column; grid-auto-columns: 1fr; gap: 2px;
  padding: 2px; border-radius: var(--radius-input);
  background: var(--bg-base); border: 1px solid var(--border);
}
.seg-b {
  display: inline-flex; align-items: center; justify-content: center; gap: 4px;
  padding: 4px 6px; border: none; border-radius: 6px; cursor: pointer;
  background: transparent; color: var(--text-dimmed);
  font: 500 11px/1.4 var(--font-sans); white-space: nowrap;
  transition: background var(--dur) var(--ease), color var(--dur) var(--ease);
}
.seg-b:hover { color: var(--text-primary); background: var(--bg-elevated); }
.seg-b.is-on {
  background: var(--bg-raised); color: var(--text-primary); font-weight: 600;
  box-shadow: 0 1px 2px rgba(0,0,0,.25), inset 0 1px 0 var(--inset-top);
}
.seg-quiet .seg-b { font-size: 10.5px; padding: 3px 6px; }
.seg .dot { width: 5px; height: 5px; border-radius: 50%; background: currentColor; flex: none; }
.seg-b .dot.d-Easy { background: var(--easy); }
.seg-b .dot.d-Medium { background: var(--medium); }
.seg-b .dot.d-Hard { background: var(--hard); }

.topic-pill {
  display: flex; align-items: center; gap: 6px; margin-top: 8px;
  padding: 4px 4px 4px 10px; border-radius: var(--radius-chip);
  background: var(--accent-subtle); border: 1px solid var(--accent);
  color: var(--accent-text); font-size: var(--fs-body-s); font-weight: 600;
}
.topic-pill-t { flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.topic-pill-x {
  display: flex; align-items: center; justify-content: center;
  width: 20px; height: 20px; flex: 0 0 20px; padding: 0;
  border: none; border-radius: var(--radius-chip);
  background: transparent; color: inherit; cursor: pointer; opacity: .75;
}
.topic-pill-x:hover { background: var(--bg-elevated); opacity: 1; }

.tp-head-actions { margin-left: auto; display: flex; align-items: center; gap: 6px; flex: 0 0 auto; }

.rail-list { flex: 1; overflow-y: auto; padding: 6px 6px 14px; scrollbar-width: thin; }
.rail-sec { display: flex; flex-direction: column; }

/* Group headers stay put while their rows scroll under them. */
.rail-group {
  position: sticky; top: 0; z-index: 2;
  display: flex; align-items: center; gap: 7px; width: 100%;
  padding: 9px 9px 7px; margin-top: 6px; cursor: pointer;
  border: none; border-bottom: 1px solid var(--rail-head-line);
  border-radius: var(--radius-card-sm) var(--radius-card-sm) 0 0;
  background: var(--bg-surface); color: var(--rail-head);
  font: 700 10.5px/1.4 var(--font-mono); letter-spacing: .1em; text-transform: uppercase;
  text-align: left; transition: color var(--dur) var(--ease), background var(--dur) var(--ease);
}
.rail-group::before {
  content: ''; width: 3px; height: 11px; border-radius: 2px; flex: none;
  background: var(--rail-head-mark);
}
.rail-group:hover { background: var(--bg-elevated); }
.rail-sec.is-shut .rail-group { border-bottom-color: transparent; }
.rail-group-x {
  display: flex; flex: none; transform: rotate(90deg);
  color: var(--rail-head-mark); opacity: .8;
  transition: transform var(--dur) var(--ease);
}
.rail-sec.is-shut .rail-group-x { transform: rotate(0deg); }
.rail-group-t {
  overflow: hidden; text-overflow: ellipsis; white-space: nowrap; min-width: 0;
}
.rail-meter {
  flex: 1 1 26px; min-width: 18px; height: 3px; border-radius: 2px;
  background: var(--border); overflow: hidden;
}
.rail-meter-f {
  display: block; height: 100%; border-radius: 2px; background: var(--accent);
  transition: width .35s var(--ease);
}
.rail-meter-f.is-done { background: var(--success); }
.rail-group-n {
  flex: none; color: var(--text-dimmed); letter-spacing: 0; font-size: 10px;
  font-variant-numeric: tabular-nums;
}
.rail-group-n.is-done { color: var(--success); }

.rail-rows { display: flex; flex-direction: column; gap: 1px; }
.rail-sec.is-shut .rail-rows { display: none; }

.p-item {
  display: flex; align-items: center; gap: 9px; padding: 7px 10px;
  border-radius: var(--radius-card-sm); cursor: pointer; border: 1px solid transparent;
  outline: none; position: relative;
  transition: background var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}
.p-item:hover { background: var(--bg-elevated); }
.p-item:focus-visible { background: var(--bg-elevated); box-shadow: var(--shadow-focus); }
.p-item.is-on {
  background: var(--accent-subtle); border-color: var(--accent-line);
  box-shadow: inset 2px 0 0 var(--accent);
}
.p-item .stat { width: 14px; flex: 0 0 14px; color: var(--text-dimmed); display: flex; }
.p-item.solved .stat { color: var(--success); }
.p-item .p-name {
  flex: 1; font-size: var(--fs-body-m); overflow: hidden; text-overflow: ellipsis;
  white-space: nowrap; color: var(--text-secondary); min-width: 0;
}
.p-item.is-on .p-name, .p-item:hover .p-name, .p-item:focus-visible .p-name { color: var(--text-primary); }
.p-item.solved .p-name { color: var(--text-dimmed); }
.p-num {
  flex: none; font: 9.5px/1.5 var(--font-mono); color: var(--text-dimmed);
  padding: 1px 4px; border-radius: 4px; background: var(--bg-base);
  border: 1px solid var(--border); opacity: 0;
  transition: opacity var(--dur) var(--ease);
}
.p-item:hover .p-num, .p-item.is-on .p-num { opacity: 1; }
.p-item .p-diff {
  flex: none; font-size: 10.5px; font-weight: 700; font-family: var(--font-mono); width: 9px;
}
.d-Easy { color: var(--easy); } .d-Medium { color: var(--medium); } .d-Hard { color: var(--hard); }

.rail-none {
  display: flex; flex-direction: column; align-items: flex-start; gap: 9px;
  padding: 22px 14px; color: var(--text-dimmed); font-size: var(--fs-body-m);
}
.rail-none p { margin: 0; }
.rail-none b { color: var(--text-primary); }

.rail-foot {
  padding: 9px 12px; border-top: 1px solid var(--border); display: flex; align-items: center;
  justify-content: space-between; font-size: 11.5px; color: var(--text-dimmed); font-family: var(--font-mono);
}

/* ── panes ───────────────────────────────────────────────── */
.pane { display: flex; flex-direction: column; overflow: hidden; background: var(--bg-base); }
.pane-problem { background: var(--bg-surface); }
.pane-head {
  height: 40px; flex: 0 0 40px; display: flex; align-items: center; gap: 8px; padding: 0 12px;
  border-bottom: 1px solid var(--border); background: var(--bg-surface);
}
.spacer { flex: 1; }
.tabbar { display: flex; gap: 2px; height: 100%; align-items: center; }
.tab {
  background: transparent; border: none; border-bottom: 2px solid transparent;
  color: var(--text-dimmed); padding: 0 12px; height: 100%; cursor: pointer;
  font-size: var(--fs-body-m); transition: color .12s;
}
.tab:hover { color: var(--text-primary); }
.tab.is-on { color: var(--accent-text); border-bottom-color: var(--accent); font-weight: 600; }
.tabbar.sm .tab { font-size: var(--fs-body-s); padding: 0 10px; }
.pane-body { flex: 1; overflow-y: auto; position: relative; }
.panel { display: none; padding: 22px 26px 60px; max-width: 820px; }
.panel.is-on { display: block; }

/* ── problem document ────────────────────────────────────── */
.panel { display: none; padding: 0 0 64px; max-width: none; }
.panel.is-on { display: block; }
.panel > .prose, .panel > .block, .panel > .sol-switch,
.panel > .sol-panel, .panel > .empty { padding-inline: 26px; }
.panel > .prose { max-width: 68ch; }

.prob-head {
  padding: 22px 26px 16px; border-bottom: 1px solid var(--border);
  margin-bottom: 20px; background: var(--bg-surface);
}
.prob-head-row { display: flex; align-items: flex-start; gap: 16px; }
.prob-title {
  font-size: var(--fs-heading-xl); line-height: var(--lh-heading-xl);
  font-weight: 700; margin: 0; flex: 1; letter-spacing: -.01em;
}
.prob-state {
  display: flex; align-items: center; gap: 6px; flex: 0 0 auto;
  font-size: 11px; font-weight: 700; letter-spacing: .04em; text-transform: uppercase;
  padding: 4px 10px; border-radius: var(--radius-chip);
  border: 1px solid var(--border); color: var(--text-dimmed); background: var(--bg-base);
}
.prob-state.is-solved {
  color: var(--success); border-color: color-mix(in oklab, var(--success) 45%, transparent);
  background: color-mix(in oklab, var(--success) 12%, transparent);
}
.prob-meta { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; margin-top: 10px; }
.badge {
  padding: 3px 10px; border-radius: var(--radius-chip); font-size: 11px; font-weight: 700;
  border: 1px solid var(--border); background: var(--bg-elevated); color: var(--text-secondary);
  letter-spacing: .02em;
}
.badge.d-Easy { color: var(--easy); border-color: color-mix(in oklab, var(--easy) 40%, transparent); }
.badge.d-Medium { color: var(--medium); border-color: color-mix(in oklab, var(--medium) 30%, transparent); }
.badge.d-Hard { color: var(--hard); border-color: color-mix(in oklab, var(--hard) 40%, transparent); }
.badge.src { color: var(--accent-text); border-color: color-mix(in oklab, var(--accent) 40%, transparent); background: var(--accent-subtle); }

.block { margin-top: 26px; }
.block-h {
  font-size: 11px; letter-spacing: .1em; text-transform: uppercase;
  color: var(--text-dimmed); margin: 0 0 10px; font-weight: 700; font-family: var(--font-mono);
}

/* Examples are one list, so they live in one card separated by rules. */
.ex-card {
  border: 1px solid var(--border); border-radius: var(--radius-card); overflow: hidden;
  background: var(--bg-elevated); box-shadow: var(--shadow-sm), inset 0 1px 0 var(--inset-top);
}
.ex-row { display: flex; gap: 12px; padding: 12px 14px; }
.ex-row + .ex-row { border-top: 1px solid var(--hairline); }
.ex-n {
  flex: 0 0 20px; height: 20px; border-radius: 50%; background: var(--bg-elevated);
  color: var(--text-secondary); font: 700 10px/20px var(--font-mono); text-align: center;
}
.ex-kv { display: grid; grid-template-columns: 58px 1fr; gap: 3px 10px; margin: 0; flex: 1; min-width: 0; }
.ex-kv dt { color: var(--text-dimmed); font: 11px/1.6 var(--font-mono); }
.ex-kv dd { margin: 0; color: var(--text-primary); font: 12.5px/1.6 var(--font-mono); white-space: pre-wrap; word-break: break-word; }
.ex-kv dd.ex-note { color: var(--text-secondary); font: var(--fs-body-m)/1.55 var(--font-sans); }

.constraints { display: flex; flex-wrap: wrap; gap: 6px; }
.constraints code {
  font-family: var(--font-mono); font-size: 12px; background: var(--bg-base);
  border: 1px solid var(--border); color: var(--text-secondary);
  padding: 4px 9px; border-radius: var(--radius-badge);
}

.hintbox {
  border: 1px solid var(--border); border-radius: var(--radius-card-sm);
  margin: 0 0 6px; background: var(--bg-base); overflow: hidden;
}
.hintbox summary {
  padding: 9px 13px; cursor: pointer; font-size: var(--fs-body-m); color: var(--text-secondary);
  user-select: none; display: flex; align-items: center; gap: 8px; font-weight: 600;
  list-style: none;
}
.hintbox summary::-webkit-details-marker { display: none; }
.hintbox summary .ico { color: var(--text-dimmed); transition: transform .18s; }
.hintbox[open] summary .ico { transform: rotate(90deg); }
.hintbox[open] summary { border-bottom: 1px solid var(--border); color: var(--text-primary); }
.hintbox .hint-b { padding: 12px 14px; color: var(--text-secondary); font-size: var(--fs-body-m); }
.hintbox .hint-b p:last-child { margin-bottom: 0; }

/* ── prose ───────────────────────────────────────────────── */
.prose { color: var(--text-primary); font-size: var(--fs-heading-s); line-height: 1.65; }
.prose p { margin: 0 0 12px; }
.prose p:last-child { margin-bottom: 0; }
.prose ul, .prose ol { margin: 0 0 12px; padding-left: 22px; }
.prose li { margin: 5px 0; }
.prose li::marker { color: var(--text-dimmed); }
.prose code {
  font-family: var(--font-mono); font-size: 12.5px; background: var(--bg-elevated);
  padding: 1.5px 5px; border-radius: var(--radius-badge); border: 1px solid var(--border);
  color: var(--accent-text);
}
.prose pre {
  background: var(--bg-base); border: 1px solid var(--border); border-radius: var(--radius-card-sm);
  padding: 12px 14px; overflow-x: auto; margin: 0 0 14px;
}
.prose pre code { background: none; border: none; padding: 0; color: var(--text-primary); font-size: 12.5px; line-height: 1.7; display: block; }
.prose strong { color: var(--text-primary); font-weight: 700; }
.prose table { border-collapse: collapse; width: 100%; margin: 0 0 14px; font-size: var(--fs-body-m); }
.prose th, .prose td { border: 1px solid var(--border); padding: 7px 10px; text-align: left; }
.prose th { background: var(--bg-elevated); color: var(--text-secondary); font-size: var(--fs-body-s); }
.prose blockquote { margin: 0 0 14px; padding: 2px 0 2px 14px; border-left: 3px solid var(--border-hover); color: var(--text-secondary); }

/* ── solutions: a switcher, one panel at a time ──────────── */
.sol-switch {
  display: flex; gap: 6px; flex-wrap: wrap; padding-block: 18px 16px;
  border-bottom: 1px solid var(--border); margin-bottom: 22px;
  position: sticky; top: 0; z-index: 5;
  background: color-mix(in oklab, var(--surface-1) 82%, transparent);
  backdrop-filter: blur(16px) saturate(150%);
  -webkit-backdrop-filter: blur(16px) saturate(150%);
}
.sol-pill {
  display: flex; align-items: center; gap: 8px; padding: 7px 12px;
  border: 1px solid var(--border); border-radius: var(--radius-chip);
  background: var(--bg-base); cursor: pointer; color: var(--text-secondary);
  transition: border-color .12s, background .12s, color .12s;
}
.sol-pill:hover { border-color: var(--border-hover); color: var(--text-primary); }
.sol-pill.is-on { background: var(--accent-subtle); border-color: var(--accent); color: var(--text-primary); }
.sol-pill-n {
  width: 18px; height: 18px; border-radius: 50%; background: var(--bg-elevated);
  font: 700 10px/18px var(--font-mono); text-align: center; color: var(--text-secondary);
}
.sol-pill.is-on .sol-pill-n { background: var(--accent); color: var(--accent-ink); }
.sol-pill-t { font-size: var(--fs-body-m); font-weight: 600; }
.sol-pill-cx { font-family: var(--font-mono); font-size: 11px; color: var(--text-dimmed); }
.sol-pill.is-on .sol-pill-cx { color: var(--accent-text); }

.sol-panel { display: none; }
.sol-panel.is-on { display: block; }
.sol-head { margin-bottom: 16px; }
.sol-title { font-size: var(--fs-heading-m); line-height: var(--lh-heading-m); font-weight: 700; margin: 0 0 10px; }
.metrics { display: flex; gap: 8px; flex-wrap: wrap; }
.metric {
  display: flex; align-items: baseline; gap: 7px; padding: 5px 11px;
  border: 1px solid var(--border); border-radius: var(--radius-badge); background: var(--bg-base);
}
.metric span { font-size: 10.5px; text-transform: uppercase; letter-spacing: .08em; color: var(--text-dimmed); }
.metric b { font-family: var(--font-mono); font-size: 12.5px; color: var(--accent-text); font-weight: 700; }
.metric.is-best {
  color: var(--success); border-color: color-mix(in oklab, var(--success) 45%, transparent);
  background: color-mix(in oklab, var(--success) 12%, transparent);
  font-size: 10.5px; text-transform: uppercase; letter-spacing: .08em; font-weight: 700;
}
.sol-why { max-width: 68ch; margin-bottom: 16px; }
.sol-actions { display: flex; gap: 8px; margin-top: 14px; }

/* ── editor ──────────────────────────────────────────────── */
.editor-wrap { flex: 1 1 auto; min-height: 80px; overflow: hidden; position: relative; }
.CodeMirror {
  height: 100%; font-family: var(--font-mono); font-size: 13.5px; line-height: 1.65;
  background: var(--bg-app); color: var(--text-primary);
}
.CodeMirror-gutters { background: var(--bg-app); border-right: 1px solid var(--border); }
.CodeMirror-linenumber { color: var(--text-dimmed); }
.CodeMirror-cursor { border-left: 2px solid var(--accent); }
.CodeMirror-selected { background: var(--accent-subtle) !important; }
.CodeMirror-activeline-background { background: color-mix(in oklab, var(--text-primary) 5%, transparent); }
.CodeMirror-matchingbracket { color: var(--accent) !important; border-bottom: 1px solid var(--accent); }

/* Syntax skin — one theme, both modes, driven by the tokens above. */
.cm-s-camora .cm-keyword,
.cm-hl .cm-keyword   { color: var(--syn-keyword); font-weight: 600; }
.cm-s-camora .cm-string,
.cm-hl .cm-string    { color: var(--syn-string); }
.cm-s-camora .cm-string-2,
.cm-hl .cm-string-2  { color: var(--syn-string); }
.cm-s-camora .cm-number,
.cm-hl .cm-number    { color: var(--syn-number); }
.cm-s-camora .cm-comment,
.cm-hl .cm-comment   { color: var(--syn-comment); font-style: italic; }
.cm-s-camora .cm-def,
.cm-hl .cm-def       { color: var(--syn-def); }
.cm-s-camora .cm-variable,
.cm-hl .cm-variable  { color: var(--text-primary); }
.cm-s-camora .cm-variable-2,
.cm-hl .cm-variable-2{ color: var(--text-primary); }
.cm-s-camora .cm-builtin,
.cm-hl .cm-builtin   { color: var(--syn-builtin); }
.cm-s-camora .cm-operator,
.cm-hl .cm-operator  { color: var(--syn-operator); }
.cm-s-camora .cm-property,
.cm-hl .cm-property  { color: var(--text-primary); }
.cm-s-camora .cm-meta,
.cm-hl .cm-meta      { color: var(--text-dimmed); }
.cm-hl {
  background: var(--bg-base); border: 1px solid var(--border); border-radius: var(--radius-card-sm);
  padding: 12px 14px; overflow-x: auto; margin: 0; font-family: var(--font-mono);
  font-size: 12.5px; line-height: 1.7; color: var(--text-primary);
}
.cm-hl code { font-family: inherit; }

/* ── console ─────────────────────────────────────────────── */
.console { flex: 0 0 38%; min-height: 90px; display: flex; flex-direction: column; background: var(--bg-surface); border-top: 1px solid var(--border); }
.console-head { height: 36px; flex: 0 0 36px; display: flex; align-items: center; padding: 0 8px; border-bottom: 1px solid var(--border); }
.timing { font-family: var(--font-mono); font-size: 11px; color: var(--text-dimmed); margin-right: 8px; }
.console-body { flex: 1; overflow: auto; position: relative; }
.out {
  display: none; padding: 11px 13px; margin: 0; font-family: var(--font-mono);
  font-size: 12.5px; line-height: 1.65; white-space: pre-wrap; word-break: break-word; min-height: 100%;
}
.out.is-on { display: block; }
/* The console is preformatted text; the results pane is markup. Left as
   pre-wrap, every newline and indent in the results template rendered as
   real whitespace and pushed the cards apart. */
#out-results { white-space: normal; padding: 12px; }
#out-stdin { padding: 0; }
.stdin {
  width: 100%; height: 100%; min-height: 120px; border: none; outline: none; resize: none;
  padding: 11px 13px; background: transparent; color: var(--text-primary);
  font: 12.5px/1.65 var(--font-mono);
}
.stdin::placeholder { color: var(--text-dimmed); }
.empty { color: var(--text-dimmed); font-family: var(--font-sans); font-style: italic; }
.err { color: var(--danger); }
.sys { color: var(--text-dimmed); }

/* ── results: verdict first, failures next, passes folded away ── */
.verdict {
  padding: 12px 14px; border-radius: var(--radius-card-sm); margin-bottom: 12px;
  border: 1px solid var(--border); background: var(--bg-base); font-family: var(--font-sans);
}
.verdict.is-pass {
  border-color: color-mix(in oklab, var(--success) 50%, transparent);
  background: color-mix(in oklab, var(--success) 10%, transparent);
}
.verdict.is-fail {
  border-color: color-mix(in oklab, var(--danger) 50%, transparent);
  background: color-mix(in oklab, var(--danger) 10%, transparent);
}
.verdict-main { font-size: var(--fs-heading-s); font-weight: 700; line-height: 1.3; }
.verdict.is-pass .verdict-main { color: var(--success); }
.verdict.is-fail .verdict-main { color: var(--danger); }
.verdict-sub { font-size: var(--fs-body-s); color: var(--text-secondary); margin-top: 2px; }
.verdict-bar {
  height: 3px; border-radius: 2px; background: color-mix(in oklab, var(--text-primary) 12%, transparent);
  margin-top: 10px; overflow: hidden;
}
.verdict-bar span { display: block; height: 100%; border-radius: 2px; background: var(--success); transition: width .25s; }

.case-list { display: flex; flex-direction: column; gap: 6px; margin-bottom: 12px; }
.case { border: 1px solid color-mix(in oklab, var(--danger) 35%, var(--border)); border-radius: var(--radius-card-sm); overflow: hidden; background: var(--bg-base); }
.case-h {
  display: flex; align-items: center; gap: 9px; padding: 9px 12px; cursor: pointer;
  font-family: var(--font-sans); font-size: var(--fs-body-m);
}
.case-h:hover { background: var(--bg-elevated); }
.mark { width: 13px; flex: 0 0 13px; display: flex; align-items: center; justify-content: center; }
.mark.ok { color: var(--success); }
.mark.no { color: var(--danger); }
.case-name { flex: 1; color: var(--text-primary); font-weight: 600; }
.case-tier {
  font-size: 9.5px; text-transform: uppercase; letter-spacing: .08em; font-weight: 700;
  padding: 2px 6px; border-radius: var(--radius-badge);
  color: var(--warning); background: color-mix(in oklab, var(--warning) 14%, transparent);
}
.case-ms { font-family: var(--font-mono); font-size: 11px; color: var(--text-dimmed); }
.case-b { display: none; padding: 12px; border-top: 1px solid var(--border); background: var(--bg-surface); }
.case.is-open .case-b { display: block; }
.kv { display: grid; grid-template-columns: 74px 1fr; gap: 5px 12px; margin: 0; }
.kv dt { color: var(--text-dimmed); font: 10.5px/1.7 var(--font-mono); text-transform: uppercase; letter-spacing: .06em; }
.kv dd { margin: 0; white-space: pre-wrap; word-break: break-word; font: 12.5px/1.7 var(--font-mono); color: var(--text-secondary); }
.kv dd.want { color: var(--success); }
.kv dd.got { color: var(--danger); }
.case-out { margin-top: 10px; }
.case-out span {
  font: 10.5px/1.7 var(--font-mono); text-transform: uppercase; letter-spacing: .06em; color: var(--text-dimmed);
}
.case-out pre, .trace {
  margin: 4px 0 0; padding: 10px 12px; border-radius: var(--radius-badge);
  background: var(--bg-base); border: 1px solid var(--border);
  font: 12px/1.65 var(--font-mono); white-space: pre-wrap; word-break: break-word;
  color: var(--text-secondary); overflow-x: auto;
}
.trace { color: var(--danger); }

/* Passing cases are reassurance, not reading material. */
.tier-note {
  margin: 10px 0 0; padding: 9px 12px; border-radius: var(--radius-card-sm);
  border: 1px solid var(--border); background: var(--bg-surface);
  color: var(--text-secondary); font-size: var(--fs-body-s); line-height: 1.55;
}

.passed-strip { border: 1px solid var(--border); border-radius: var(--radius-card-sm); overflow: hidden; background: var(--bg-base); }
.passed-h {
  padding: 7px 12px; background: var(--bg-elevated); color: var(--text-secondary);
  font: 700 10.5px/1.6 var(--font-mono); text-transform: uppercase; letter-spacing: .08em;
}
.passed-row { display: flex; align-items: center; gap: 9px; padding: 5px 12px; }
.passed-row + .passed-row { border-top: 1px solid color-mix(in oklab, var(--border) 60%, transparent); }
.passed-name { flex: 1; font-size: var(--fs-body-s); color: var(--text-secondary); }
.passed-ms { font-family: var(--font-mono); font-size: 10.5px; color: var(--text-dimmed); }

/* ── notes ───────────────────────────────────────────────── */
.notes-box {
  width: 100%; min-height: 340px; resize: vertical; padding: 13px 14px;
  border: 1px solid var(--border); border-radius: var(--radius-card-sm);
  background: var(--bg-base); color: var(--text-primary);
  font: 13px/1.7 var(--font-mono); outline: none;
}
.notes-box:focus { border-color: var(--accent); box-shadow: var(--shadow-focus); }
.notes-box::placeholder { color: var(--text-dimmed); }

/* ── boot veil ───────────────────────────────────────────── */
.boot-veil {
  position: fixed; inset: 0; background: color-mix(in oklab, var(--bg-base) 88%, transparent);
  backdrop-filter: blur(3px); display: grid; place-items: center; z-index: 50; transition: opacity .3s;
}
.boot-veil.gone { opacity: 0; pointer-events: none; }
.boot-card { text-align: center; max-width: 420px; padding: 28px; }
.boot-card h2 { margin: 16px 0 8px; font-size: var(--fs-heading-m); font-weight: 700; }
.boot-card p { margin: 0; color: var(--text-dimmed); font-size: var(--fs-body-m); }
.boot-spin {
  width: 34px; height: 34px; margin: 0 auto; border-radius: 50%;
  border: 3px solid var(--border); border-top-color: var(--accent); animation: spin .8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg) } }

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; }
}

/* ── responsive ──────────────────────────────────────────── */
@media (max-width: 1100px) {
  .layout { grid-template-columns: 1fr; grid-template-rows: auto; overflow-y: auto; height: auto; }
  .rail-grip, .col-grip { display: none; }
  /* The rail used to be display:none from here down, which left a narrow window
     with no way to reach the catalogue, the search box or the filter chips at
     all. It becomes a normal block above the panes instead. */
  .rail { border-right: 0; border-bottom: 1px solid var(--border); max-height: 44vh; }
  .pane { height: auto; }
  .pane-work { height: 78vh; }
  .brand-sub { display: none; }
  .panel { padding: 18px 16px 48px; }
}

@media (max-width: 760px) {
  /* Brand + three labelled tabs + status do not fit; the whole page was pushed
     ~100px wider than the screen. The tab icons carry the meaning on their own. */
  .topbar { gap: 10px; padding: 0 10px; }
  .brand-name { display: none; }
  .mode-tabs { margin-left: 0; }
  .mode-tab { padding: 5px 9px; gap: 0; }
  .mode-tab span { display: none; }
  .editor-head { flex-wrap: wrap; height: auto; padding-block: 6px; row-gap: 6px; }
  .rmv-head { padding: 18px 16px 14px; }
  .rmv-graph { padding: 18px 12px 28px; }
}

/* ── mode switch ─────────────────────────────────────────── */
.mode-tabs { display: flex; gap: 3px; margin-left: 6px; padding: 3px; border-radius: var(--radius-chip); background: var(--bg-elevated); }
.mode-tab {
  display: flex; align-items: center; gap: 7px; padding: 5px 14px;
  border: none; border-radius: var(--radius-chip); background: transparent;
  color: var(--text-secondary); cursor: pointer; font-size: var(--fs-body-m); font-weight: 600;
  transition: background var(--dur) var(--ease), color var(--dur) var(--ease);
}
.mode-tab:hover { color: var(--text-primary); }
.mode-tab.is-on { background: var(--bg-base); color: var(--accent-text); box-shadow: var(--shadow-xs); }

/* ── playground view ─────────────────────────────────────── */
.pgv { height: calc(100vh - 48px); display: flex; flex-direction: column; background: var(--bg-base); }
.pgv-bar {
  height: 46px; flex: 0 0 46px; display: flex; align-items: center; gap: 8px;
  padding: 0 14px; border-bottom: 1px solid var(--border); background: var(--bg-surface);
}
.lang-tabs { display: flex; gap: 4px; }
.lang-tab {
  display: flex; align-items: center; gap: 7px; padding: 5px 13px;
  border: 1px solid var(--border); border-radius: var(--radius-chip);
  background: var(--bg-base); color: var(--text-secondary); cursor: pointer;
  font-size: var(--fs-body-m); font-weight: 600;
  transition: border-color var(--dur) var(--ease), color var(--dur) var(--ease), background var(--dur) var(--ease);
}
.lang-tab:hover { border-color: var(--border-hover); color: var(--text-primary); }
.lang-tab.is-on { background: var(--accent-subtle); border-color: var(--accent); color: var(--text-primary); }
.pgv-editor { flex: 1 1 auto; min-height: 120px; overflow: hidden; }
.pgv-console { flex: 0 0 38%; min-height: 120px; display: flex; flex-direction: column; background: var(--bg-surface); border-top: 1px solid var(--border); }
.pgv-console .console-body { flex: 1; overflow: auto; }
.sh-note {
  padding: 10px 13px; margin: 0 0 10px; border-radius: var(--radius-card-sm);
  border: 1px solid var(--border); border-left: 3px solid var(--accent);
  background: var(--bg-base); color: var(--text-secondary);
  font: var(--fs-body-s)/1.6 var(--font-sans); white-space: normal;
}
.sh-note b { color: var(--text-primary); font-weight: 600; }

/* ── richer solution sections ────────────────────────────── */
.sol-extra {
  margin-top: 18px; padding: 14px 16px; border-radius: var(--radius-card-sm);
  background: var(--bg-elevated); border: 1px solid var(--border);
}
.sol-extra.is-warn { border-left: 3px solid var(--warning); }
.extra-h {
  margin: 0 0 10px; font: 700 10.5px/1.4 var(--font-mono);
  letter-spacing: .12em; text-transform: uppercase; color: var(--text-dimmed);
}
.sol-extra.is-warn .extra-h { color: var(--warning); }
.sol-extra .prose { font-size: var(--fs-body-m); }
.sol-extra .prose table { margin-bottom: 0; font-size: 12.5px; }
.sol-extra .prose th { font-family: var(--font-mono); font-size: 11px; }
.sol-extra .prose td { font-family: var(--font-mono); font-size: 12px; }
.pitfalls { margin: 0; padding-left: 18px; }
.pitfalls li { margin: 7px 0; font-size: var(--fs-body-m); color: var(--text-secondary); line-height: 1.6; }
.when-to-use {
  margin: 16px 0 0; padding: 11px 14px; border-radius: var(--radius-card-sm);
  background: var(--accent-subtle); border: 1px solid var(--accent-line);
  font-size: var(--fs-body-m); color: var(--text-primary); line-height: 1.6;
}
.when-to-use span {
  display: block; font: 700 10.5px/1.4 var(--font-mono); letter-spacing: .12em;
  text-transform: uppercase; color: var(--accent-text); margin-bottom: 5px;
}

/* ── execution visualiser ────────────────────────────────── */
.viz-empty { padding: 16px; color: var(--text-dimmed); font-family: var(--font-sans); font-style: italic; }
.viz-empty.err { color: var(--danger); font-style: normal; }
.viz-bar {
  display: flex; align-items: center; gap: 12px; padding: 9px 12px;
  border-bottom: 1px solid var(--border); background: var(--bg-elevated);
}
.viz-count { font: 600 11.5px/1 var(--font-mono); color: var(--text-secondary); min-width: 92px; }
.viz-controls { display: flex; gap: 4px; margin-inline: auto; }
.viz-btn {
  width: 30px; height: 26px; border-radius: var(--radius-badge); cursor: pointer;
  border: 1px solid var(--border); background: var(--bg-base); color: var(--text-secondary);
  font-size: 11px; display: grid; place-items: center; transition: all var(--dur) var(--ease);
}
.viz-btn:hover { border-color: var(--border-hover); color: var(--text-primary); }
.viz-btn.is-play { background: var(--accent); border-color: transparent; color: var(--accent-ink); }
.viz-speeds { display: flex; gap: 2px; }
.viz-speed {
  padding: 4px 9px; border-radius: var(--radius-badge); cursor: pointer; border: 1px solid transparent;
  background: transparent; color: var(--text-dimmed); font: 600 11px/1 var(--font-mono);
}
.viz-speed.is-on { background: var(--accent-subtle); border-color: var(--accent-line); color: var(--accent-text); }
.viz-scrub { width: calc(100% - 24px); margin: 10px 12px 4px; accent-color: var(--accent); }
.viz-io {
  display: flex; align-items: center; gap: 8px; flex-wrap: wrap;
  padding: 6px 12px 10px; border-bottom: 1px solid var(--border);
  font: 11.5px/1.6 var(--font-mono); color: var(--text-dimmed);
}
.viz-io code {
  background: var(--bg-base); border: 1px solid var(--border); color: var(--text-primary);
  padding: 2px 7px; border-radius: var(--radius-badge); font-size: 11.5px;
}
.viz-vars { display: flex; flex-direction: column; gap: 5px; padding: 12px; }
.viz-var {
  display: grid; grid-template-columns: 110px 1fr; gap: 12px; align-items: baseline;
  padding: 7px 11px; border-radius: var(--radius-badge);
  background: var(--bg-base); border: 1px solid var(--border);
}
.viz-name { font: 600 11px/1.5 var(--font-mono); color: var(--accent-text); }
.viz-val { font: 12.5px/1.5 var(--font-mono); color: var(--text-primary); word-break: break-all; }
.viz-note { margin: 0; padding: 0 12px 12px; font-size: 11.5px; color: var(--text-dimmed); }

/* ── roadmap ─────────────────────────────────────────────── */
.rmv { height: calc(100vh - 48px); display: flex; flex-direction: column; overflow: hidden; }
.rmv-head { padding: 24px 26px 18px; border-bottom: 1px solid var(--border); background: var(--bg-surface); }
.rmv-head h1 { margin: 0 0 4px; font-size: var(--fs-heading-l); font-weight: 700; }
.rmv-head p { margin: 0 0 14px; color: var(--text-secondary); font-size: var(--fs-body-m); }
.rmv-overall { display: flex; align-items: center; gap: 12px; max-width: 560px; }
.rmv-bar { flex: 1; height: 5px; border-radius: 3px; background: var(--bg-raised); overflow: hidden; }
.rmv-bar span { display: block; height: 100%; background: var(--success); border-radius: 3px; transition: width .3s var(--ease); }
.rmv-count { font: 11.5px/1 var(--font-mono); color: var(--text-dimmed); white-space: nowrap; }
.rmv-body { flex: 1; display: flex; overflow: hidden; }
.rmv-graph {
  flex: 1; overflow-y: auto; padding: 26px 20px 34px; position: relative;
  display: flex; flex-direction: column; gap: 34px; align-items: stretch;
}
.rmv-tier { display: flex; gap: 16px; flex-wrap: wrap; justify-content: center; row-gap: 34px; }
.rmv-node {
  position: relative; z-index: 1; min-width: 170px; flex: 0 1 190px; max-width: 240px;
  text-align: left; cursor: pointer;
  padding: 12px 14px 14px; border-radius: var(--radius-card);
  border: 1px solid var(--border); background: var(--bg-elevated);
  box-shadow: var(--shadow-xs), inset 0 1px 0 var(--inset-top);
  transition: border-color var(--dur) var(--ease), transform var(--dur) var(--ease);
}
.rmv-node:hover:not([disabled]) { border-color: var(--accent); transform: translateY(-1px); }
.rmv-node[disabled] { opacity: .45; cursor: not-allowed; }
.rmv-node.is-done { border-color: color-mix(in oklab, var(--success) 45%, transparent); }
.rmv-label { display: block; font-size: var(--fs-body-m); font-weight: 600; color: var(--text-primary); }
.rmv-meta { display: block; margin-top: 3px; font: 11px/1.4 var(--font-mono); color: var(--text-dimmed); }
.rmv-track { display: block; margin-top: 9px; height: 3px; border-radius: 2px; background: var(--bg-base); overflow: hidden; }
.rmv-track span { display: block; height: 100%; background: var(--accent); border-radius: 2px; }
.rmv-node.is-done .rmv-track span { background: var(--success); }

.rmv-panel {
  width: 380px; flex: 0 0 380px; overflow-y: auto; padding: 22px;
  border-left: 1px solid var(--border); background: var(--bg-surface);
}
.tp-head { display: flex; align-items: flex-start; gap: 12px; margin-bottom: 20px; }
.tp-head h2 { margin: 0; font-size: var(--fs-heading-m); font-weight: 700; }
.tp-head p { margin: 3px 0 0; font: 11.5px/1.5 var(--font-mono); color: var(--text-dimmed); }
.tp-head-actions .btn { margin-left: 0; }
.tp-block { margin-bottom: 22px; }
.tp-prereqs { display: flex; flex-direction: column; gap: 7px; }
.tp-prereq {
  padding: 10px 12px; border-radius: var(--radius-card-sm);
  border: 1px solid var(--border); background: var(--bg-base);
}
.tp-prereq-n { display: block; font-size: var(--fs-body-m); font-weight: 600; color: var(--accent-text); }
.tp-prereq-w { display: block; margin-top: 3px; font-size: var(--fs-body-s); color: var(--text-secondary); line-height: 1.55; }
.tp-list { display: flex; flex-direction: column; gap: 3px; }
.tp-row {
  display: flex; align-items: center; gap: 9px; width: 100%; text-align: left; cursor: pointer;
  padding: 8px 10px; border-radius: var(--radius-card-sm); border: 1px solid transparent; background: transparent;
}
.tp-row:hover { background: var(--bg-elevated); }
.tp-mark { display: flex; color: var(--text-dimmed); }
.tp-row.is-solved .tp-mark { color: var(--success); }
.tp-name { flex: 1; font-size: var(--fs-body-m); color: var(--text-secondary); }
.tp-row:hover .tp-name { color: var(--text-primary); }
.tp-diff { font: 700 10px/1 var(--font-mono); text-transform: uppercase; letter-spacing: .04em; }
@media (max-width: 1000px) { .rmv-panel { display: none; } }

/* ── visualiser: drawn state ─────────────────────────────── */
.viz-var { display: grid; grid-template-columns: 96px 1fr; gap: 12px; align-items: start;
  padding: 9px 11px; border-radius: var(--radius-card-sm);
  background: var(--bg-base); border: 1px solid var(--border); }
.viz-var.is-scalar { align-items: center; }
.viz-body { min-width: 0; }
.viz-scalar { font: 600 13px/1.4 var(--font-mono); color: var(--text-primary); }
.viz-none { font: italic 12px/1.4 var(--font-sans); color: var(--text-dimmed); }
.viz-repr { font: 12px/1.5 var(--font-mono); color: var(--text-secondary); word-break: break-all; }

.cells { display: flex; flex-wrap: wrap; gap: 4px; }
.cell {
  position: relative; min-width: 38px; padding: 5px 7px 3px; text-align: center;
  border-radius: var(--radius-badge); border: 1px solid var(--border); background: var(--bg-elevated);
  transition: border-color var(--dur) var(--ease), background var(--dur) var(--ease);
}
.cell-v { display: block; font: 600 12.5px/1.3 var(--font-mono); color: var(--text-primary); }
.cell-i { display: block; font: 9.5px/1.3 var(--font-mono); color: var(--text-dimmed); }
.cell.is-marked { border-color: var(--accent); background: var(--accent-subtle); }
.cell-p {
  display: block; margin-top: 2px; font: 700 9.5px/1.2 var(--font-mono);
  color: var(--accent-text); letter-spacing: .04em;
}
.cell.is-more { display: grid; place-items: center; color: var(--text-dimmed); font: 11px var(--font-mono); }

.pairs { display: flex; flex-wrap: wrap; gap: 4px; }
.pair {
  display: inline-flex; align-items: center; gap: 3px; padding: 4px 8px;
  border-radius: var(--radius-badge); border: 1px solid var(--border);
  background: var(--bg-elevated); font: 12px/1.3 var(--font-mono); color: var(--text-primary);
}
.pair b { color: var(--accent-text); font-weight: 700; }
.pair i { color: var(--text-dimmed); font-style: normal; }
.pair.is-more { color: var(--text-dimmed); }
.pair.is-marked { border-color: var(--accent); background: var(--accent-subtle); }
.pair-p {
  margin-left: 4px; padding-left: 5px; border-left: 1px solid var(--border);
  font: 700 9.5px/1.2 var(--font-mono); color: var(--accent-text);
  font-style: normal; letter-spacing: .04em;
}

/* ── spoon-fed solution sections ─────────────────────────── */
.prereq-strip { margin: 0 0 22px; }
.sol-extra.is-idea { border-left: 3px solid var(--accent); background: var(--accent-subtle); }
.sol-extra.is-idea .extra-h { color: var(--accent-text); }
.algo { margin: 0; padding-left: 20px; counter-reset: none; }
.algo li { margin: 8px 0; font-size: var(--fs-body-m); color: var(--text-secondary); line-height: 1.65; }
.algo li::marker { color: var(--accent-text); font-weight: 700; font-family: var(--font-mono); }
.sol-figure {
  margin: 18px 0 0; padding: 16px; border-radius: var(--radius-card);
  border: 1px solid var(--border); background: var(--bg-base); overflow-x: auto;
}
.sol-figure svg { display: block; max-width: 100%; height: auto; margin: 0 auto; }
.sol-figure figcaption {
  margin-top: 12px; padding-top: 10px; border-top: 1px solid var(--hairline);
  font-size: var(--fs-body-s); color: var(--text-dimmed); line-height: 1.6; text-align: center;
}

/* ── roadmap edges ───────────────────────────────────────── */
.rmv-graph { position: relative; }
.rmv-edges { position: absolute; inset: 0; pointer-events: none; z-index: 0; overflow: visible; }
.rmv-tier { position: relative; z-index: 1; }
.verdict.is-idle {
  border-color: color-mix(in oklab, var(--warning) 45%, transparent);
  background: color-mix(in oklab, var(--warning) 9%, transparent);
}
.verdict.is-idle .verdict-main { color: var(--warning); }

/* ── Input (stdin) tab ───────────────────────────────────── */
#out-stdin { display: none; flex-direction: column; gap: 10px; padding: 12px 14px; overflow: auto; }
#out-stdin.is-on { display: flex; }
/* ── custom-input dialog ─────────────────────────────────── */
.inputdlg {
  border: none; padding: 0; background: transparent; color: inherit;
  max-width: min(560px, calc(100vw - 32px)); width: 100%;
}
.inputdlg::backdrop { background: rgba(0, 0, 0, .55); backdrop-filter: blur(2px); }
.inputdlg-card {
  display: flex; flex-direction: column; gap: 14px; padding: 18px 20px 16px;
  border: 1px solid var(--border); border-radius: var(--radius-card);
  background: var(--bg-surface); box-shadow: var(--shadow-md);
}
.inputdlg-head { display: flex; align-items: center; gap: 12px; }
.inputdlg-head h2 { margin: 0; font-size: var(--fs-heading-s); font-weight: 700; }
.inputdlg-head .btn { margin-left: auto; }
.inputdlg-box {
  width: 100%; min-height: 116px; resize: vertical; padding: 10px 12px;
  border: 1px solid var(--border); border-radius: var(--radius-card-sm);
  background: var(--bg-base); color: var(--text-primary);
  font: 12.5px/1.6 var(--font-mono);
}
.inputdlg-box:focus { outline: none; border-color: var(--accent); }
.inputdlg-box::placeholder { color: var(--text-dimmed); }
.inputdlg-foot { display: flex; align-items: center; gap: 8px; }
.inputdlg-foot .spacer { flex: 1; }
.inputdlg-lead { margin: 0 0 8px; font-size: 12px; color: var(--text-secondary); }
.inputdlg-lead code { font: 11.5px var(--font-mono); color: var(--accent-text); }
.inputdlg-lines { margin: 0; padding-left: 18px; display: flex; flex-direction: column; gap: 3px; }
.inputdlg-lines li { font-size: 12px; color: var(--text-secondary); }
.inputdlg-lines code {
  font: 11.5px var(--font-mono); color: var(--accent-text);
  background: var(--bg-elevated); border-radius: var(--radius-badge); padding: 1px 5px;
}
.inputdlg-lines span { margin-left: 7px; color: var(--text-dimmed); }
.inputdlg-off { margin: 0; font-size: 12px; color: var(--text-dimmed); }

.stdin-spec { display: flex; flex-direction: column; gap: 8px; align-items: flex-start; }
.stdin-lead { margin: 0; font-size: 12px; color: var(--text-secondary); max-width: 62ch; }
.stdin-lead code { font: 11.5px var(--font-mono); color: var(--accent-text); }
.stdin-lines { margin: 0; padding-left: 18px; display: flex; flex-direction: column; gap: 3px; }
.stdin-lines li { font-size: 12px; color: var(--text-secondary); }
.stdin-lines code {
  font: 600 11.5px var(--font-mono); color: var(--text-primary);
  padding: 1px 5px; border-radius: var(--radius-badge);
  background: var(--bg-elevated); border: 1px solid var(--border);
}
.stdin-lines span { margin-left: 7px; color: var(--text-dimmed); }
.stdin-off { margin: 0; font-size: 12px; color: var(--text-dimmed); max-width: 62ch; }
.stdin:disabled { opacity: .5; cursor: not-allowed; }

.sol-actions { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.sol-loaded {
  margin-right: auto; font-size: 11.5px; color: var(--text-dimmed);
  display: inline-flex; align-items: center; gap: 6px;
}
.sol-loaded::before {
  content: ''; width: 6px; height: 6px; border-radius: 50%;
  background: var(--accent); flex: none;
}

/* ── "Watch it run": the step player, inside the solution ─── */
.sol-viz { display: flex; flex-direction: column; gap: 8px; }
.viz-lead { margin: 0; font-size: var(--fs-body-s); color: var(--text-dimmed); }
.viz-host { min-height: 64px; }
.viz.is-card {
  display: flex; flex-direction: column; gap: 10px;
  padding: 12px; border-radius: var(--radius-card-sm);
  border: 1px solid var(--border); background: var(--bg-base);
}
.viz.is-card .viz-bar { margin: 0; }

/* The source, with the running line marked — the card is self-contained. */
.viz-code {
  list-style: none; margin: 0; padding: 8px 0; max-height: 232px; overflow: auto;
  border-radius: var(--radius-card-sm); border: 1px solid var(--border);
  background: var(--bg-surface); counter-reset: none;
}
.viz-code li {
  display: flex; gap: 10px; padding: 1px 10px 1px 0;
  border-left: 2px solid transparent;
  font: 12px/1.65 var(--font-mono);
}
.viz-code .viz-ln {
  flex: 0 0 30px; text-align: right; color: var(--text-dimmed);
  font-size: 10.5px; user-select: none; padding-top: 1px;
}
.viz-code code { color: var(--text-secondary); white-space: pre; }
.viz-code li.is-now {
  border-left-color: var(--accent); background: var(--accent-subtle);
}
.viz-code li.is-now code { color: var(--text-primary); }
.viz-code li.is-now .viz-ln { color: var(--accent-text); font-weight: 700; }

.stdin-actions { display: flex; gap: 6px; flex-wrap: wrap; }

/* ══════════════════════════════════════════════════════════════
   Landing — what the root URL shows.

   The app used to open straight into the first problem, which gave a new
   visitor an editor and no explanation, and gave a returning one no way back
   to an overview. This is the front door: what PPG is, what it contains, and
   the one action worth taking. It sits above the workspace rather than
   replacing it, so opening a problem is a reveal, not a page load.
   ══════════════════════════════════════════════════════════════ */

.landing {
  position: fixed; inset: 0; z-index: 60;
  display: grid; place-items: center;
  padding: 32px 20px;
  background: var(--bg-base);
  overflow-y: auto;
}
.landing[hidden] { display: none; }

.landing-inner {
  width: 100%; max-width: 760px;
  display: flex; flex-direction: column; align-items: center;
  text-align: center;
}

.landing-mark {
  display: flex; align-items: center; justify-content: center;
  width: 56px; height: 56px; margin-bottom: 22px;
  border-radius: var(--radius-card);
  background: var(--accent-subtle);
  border: 1px solid var(--accent-line);
  color: var(--accent);
}

.landing h1 {
  margin: 0;
  font-size: clamp(28px, 5.2vw, 42px);
  line-height: 1.12;
  letter-spacing: -.6px;
  font-weight: 700;
  color: var(--text-primary);
}
.landing h1 em {
  font-style: normal;
  color: var(--accent-text);
}

.landing-lede {
  margin: 14px 0 0;
  max-width: 54ch;
  font-size: clamp(14px, 2.2vw, 16px);
  line-height: 1.6;
  color: var(--text-secondary);
}

.landing-stats {
  display: flex; flex-wrap: wrap; justify-content: center;
  gap: 10px; margin: 26px 0 0;
}
.landing-stat {
  display: flex; align-items: baseline; gap: 6px;
  padding: 7px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius-chip);
  background: var(--bg-elevated);
}
.landing-stat b {
  font-family: var(--font-mono);
  font-size: var(--fs-heading-xs);
  color: var(--text-primary);
}
.landing-stat span {
  font-size: var(--fs-body-s);
  color: var(--text-dimmed);
  letter-spacing: .2px;
}

.landing-actions {
  display: flex; flex-wrap: wrap; justify-content: center;
  gap: 10px; margin: 30px 0 0;
}
.landing-actions .btn { padding: 10px 20px; font-size: var(--fs-heading-xs); }

.landing-note {
  margin: 18px 0 0;
  font-size: var(--fs-body-s);
  color: var(--text-dimmed);
}

/* Three plain statements of what the thing does, not feature marketing. */
.landing-points {
  display: grid; gap: 12px; margin: 38px 0 0; width: 100%;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  text-align: left;
}
.landing-point {
  padding: 16px 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius-card-sm);
  background: var(--bg-surface);
}
.landing-point h3 {
  margin: 0 0 6px;
  font-size: var(--fs-heading-xs);
  font-weight: 600;
  color: var(--text-primary);
}
.landing-point p {
  margin: 0;
  font-size: var(--fs-body-s);
  line-height: 1.55;
  color: var(--text-muted);
}

.landing-resume {
  margin: 26px 0 0; padding-top: 22px;
  border-top: 1px solid var(--hairline);
  width: 100%;
}
.landing-resume-label {
  font-size: var(--fs-body-s);
  color: var(--text-dimmed);
  letter-spacing: .3px; text-transform: uppercase;
}
.landing-resume-list {
  display: flex; flex-wrap: wrap; justify-content: center;
  gap: 8px; margin-top: 12px;
}
.landing-resume-list button {
  padding: 6px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-chip);
  background: var(--bg-elevated);
  color: var(--text-secondary);
  font: 500 var(--fs-body-s)/1 var(--font-sans);
  cursor: pointer;
}
.landing-resume-list button:hover {
  border-color: var(--border-hover);
  color: var(--text-primary);
}

/* ── the signed-in chip in the topbar ── */
.user-chip {
  display: flex; align-items: center; gap: 8px;
  padding: 3px 4px 3px 10px;
  border: 1px solid var(--border);
  border-radius: var(--radius-chip);
  background: var(--bg-elevated);
}
.user-chip[hidden] { display: none; }
.user-chip .user-name {
  font-size: var(--fs-body-s);
  color: var(--text-secondary);
  max-width: 16ch; overflow: hidden;
  text-overflow: ellipsis; white-space: nowrap;
}
.user-chip img, .user-chip .user-initial {
  width: 24px; height: 24px; border-radius: 50%;
  display: grid; place-items: center;
  background: var(--accent-subtle);
  color: var(--accent-text);
  font-size: var(--fs-body-s); font-weight: 700;
  object-fit: cover;
}

@media (max-width: 620px) {
  .landing-points { grid-template-columns: 1fr; }
  .user-chip .user-name { display: none; }
}