:root{
  --bg:#F4F6FB;
  --surface:#FFFFFF;
  --surface-2:#ECEFF6;
  --text:#10172A;
  --text-muted:#5B6578;
  --border:#D8DEEA;
  --accent:#0E7490;
  --accent-ink:#FFFFFF;
  --accent-2:#4338CA;
  --success:#047857;
  --success-bg:#E6F7F0;
  --error:#B91C1C;
  --error-bg:#FDEDED;
  --given-bg:#EEF2F8;
  --radius:14px;
  color-scheme: light;
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    --bg:#0A0E1A;
    --surface:#121829;
    --surface-2:#1A2238;
    --text:#E7EBF5;
    --text-muted:#8C96AD;
    --border:#262F49;
    --accent:#22D3EE;
    --accent-ink:#06222A;
    --accent-2:#8B93F8;
    --success:#34D399;
    --success-bg:rgba(52,211,153,0.12);
    --error:#F87171;
    --error-bg:rgba(248,113,113,0.12);
    --given-bg:#182036;
    color-scheme: dark;
  }
}
:root[data-theme="dark"]{
  --bg:#0A0E1A;
  --surface:#121829;
  --surface-2:#1A2238;
  --text:#E7EBF5;
  --text-muted:#8C96AD;
  --border:#262F49;
  --accent:#22D3EE;
  --accent-ink:#06222A;
  --accent-2:#8B93F8;
  --success:#34D399;
  --success-bg:rgba(52,211,153,0.12);
  --error:#F87171;
  --error-bg:rgba(248,113,113,0.12);
  --given-bg:#182036;
  color-scheme: dark;
}

*{ box-sizing:border-box; }
html,body{ height:100%; }
body{
  margin:0;
  background:var(--bg);
  color:var(--text);
  font-family:"IBM Plex Sans", system-ui, sans-serif;
  padding-inline:16px;
  padding-block:28px 48px;
  min-height:100%;
}

#confetti-canvas{ position:fixed; inset:0; z-index:50; pointer-events:none; width:100%; height:100%; }

h1,h2,h3{ font-family:"Sora","IBM Plex Sans",sans-serif; text-wrap:balance; margin:0; }
.mono{ font-family:"IBM Plex Mono", ui-monospace, monospace; }

.wrap{ max-width:720px; margin:0 auto; }

.top{ display:flex; align-items:baseline; justify-content:space-between; gap:12px; margin-bottom:18px; flex-wrap:wrap; }
.top .eyebrow{ font-family:"IBM Plex Mono",monospace; font-size:12px; letter-spacing:.08em; color:var(--accent); text-transform:uppercase; }
.top h1{ font-size:25px; font-weight:700; }
.subtitle{ color:var(--text-muted); font-size:14px; margin-top:4px; }

.stat-badge{
  font-family:"IBM Plex Mono",monospace; font-size:12px; color:var(--text-muted);
  background:var(--surface-2); border:1px solid var(--border);
  border-radius:999px; padding:6px 12px; white-space:nowrap;
}
#stat-text{ color:var(--text); font-weight:500; }

.tabs{ display:flex; gap:8px; flex-wrap:wrap; margin-bottom:16px; }
.tab-btn{
  appearance:none; cursor:pointer; border:1.5px solid var(--border);
  background:var(--surface); color:var(--text-muted);
  font-family:"IBM Plex Mono",monospace; font-size:12.5px; font-weight:500;
  padding:9px 14px; border-radius:9px; letter-spacing:.02em;
  transition:all .18s ease;
}
.tab-btn:hover{ border-color:var(--accent); color:var(--text); }
.tab-btn.active{ background:var(--accent); color:var(--accent-ink); border-color:var(--accent); }

.card{
  background:var(--surface); border:1px solid var(--border); border-radius:var(--radius);
  padding:22px; box-shadow:0 1px 2px rgba(10,14,26,.04);
  animation:cardIn .4s cubic-bezier(.22,1,.36,1) both;
}
@keyframes cardIn{ from{ opacity:0; transform:translateY(8px); } to{ opacity:1; transform:translateY(0); } }

.header-meta{ display:flex; justify-content:space-between; align-items:flex-start; gap:12px; margin-bottom:18px; flex-wrap:wrap; }
.header-title{ font-size:19px; }
.header-size{ font-family:"IBM Plex Mono",monospace; font-size:12px; color:var(--text-muted); margin-top:3px; }

.legend{ display:flex; gap:14px; }
.legend-item{ display:flex; align-items:center; gap:6px; font-size:12px; color:var(--text-muted); }
.dot{ width:10px; height:10px; border-radius:3px; display:inline-block; }
.dot.given{ background:var(--given-bg); border:1px solid var(--border); }
.dot.blank{ background:var(--surface); border:1.5px dashed var(--accent); }

.diagram{ display:flex; flex-direction:column; gap:3px; margin-bottom:20px; }
.diagram.ethernet-mode{ gap:0; }

.d-row{ display:flex; gap:3px; width:100%; }
.d-row.single{ flex-wrap:wrap; }

.field{
  position:relative;
  border:1.5px solid var(--border);
  border-radius:7px;
  min-width:64px;
  display:flex; flex-direction:column; align-items:center; justify-content:center;
  padding:9px 6px 7px;
  background:var(--given-bg);
  text-align:center;
  transition:background .2s ease, border-color .2s ease, transform .15s ease;
}
.field.quizzable{ background:var(--surface); }
.field .f-label{ font-size:11.5px; font-weight:600; line-height:1.25; }
.field .f-bits{ font-family:"IBM Plex Mono",monospace; font-size:10px; color:var(--text-muted); margin-top:3px; }

.field.blank input{
  width:100%; max-width:140px;
  border:1.5px dashed var(--accent);
  border-radius:6px;
  background:transparent;
  color:var(--text);
  font-family:"IBM Plex Sans",sans-serif;
  font-size:12px; font-weight:500;
  padding:5px 6px;
  text-align:center;
  outline:none;
}
.field.blank input::placeholder{ color:var(--text-muted); opacity:.6; }
.field.blank input:focus{ border-style:solid; box-shadow:0 0 0 3px color-mix(in srgb, var(--accent) 18%, transparent); }

.field.correct{ background:var(--success-bg); border-color:var(--success); animation:popCorrect .35s ease; }
.field.correct .f-label{ color:var(--success); }
.field.wrong{ background:var(--error-bg); border-color:var(--error); animation:shake .4s ease; }
.field.wrong .f-correct{ font-size:10.5px; color:var(--error); margin-top:4px; font-weight:600; }

.field.near{ background:#FFF7E6; border-color:#D97706; animation:popCorrect .35s ease; }
.field.near .f-label{ color:#B45309; }
.field.near .f-note{ font-size:10px; color:#B45309; margin-top:3px; font-weight:600; }
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]) .field.near{ background:rgba(217,119,6,.14); border-color:#F59E0B; }
  :root:not([data-theme="light"]) .field.near .f-label,
  :root:not([data-theme="light"]) .field.near .f-note{ color:#FBBF24; }
}
:root[data-theme="dark"] .field.near{ background:rgba(217,119,6,.14); border-color:#F59E0B; }
:root[data-theme="dark"] .field.near .f-label,
:root[data-theme="dark"] .field.near .f-note{ color:#FBBF24; }

@keyframes popCorrect{ 0%{ transform:scale(1); } 40%{ transform:scale(1.06); } 100%{ transform:scale(1); } }
@keyframes shake{
  0%,100%{ transform:translateX(0); }
  20%{ transform:translateX(-4px); }
  40%{ transform:translateX(4px); }
  60%{ transform:translateX(-3px); }
  80%{ transform:translateX(3px); }
}

.actions{ display:flex; gap:10px; flex-wrap:wrap; }
.btn{
  appearance:none; border:none; cursor:pointer;
  font-family:"Sora",sans-serif; font-weight:600; font-size:14.5px;
  border-radius:10px; padding:11px 20px;
  background:var(--accent); color:var(--accent-ink);
  transition:transform .15s ease, box-shadow .15s ease;
}
.btn:hover{ transform:translateY(-1px); box-shadow:0 8px 18px rgba(14,116,144,.25); }
.btn:active{ transform:translateY(0) scale(.98); }
.btn.ghost{ background:transparent; color:var(--text); border:1px solid var(--border); }
.btn.ghost:hover{ box-shadow:none; background:var(--surface-2); }

.result-msg{
  margin-top:16px; padding:12px 14px; border-radius:10px;
  font-size:14px; font-weight:500;
  animation:fadeIn .3s ease;
}
.result-msg.good{ background:var(--success-bg); color:var(--success); }
.result-msg.bad{ background:var(--error-bg); color:var(--error); }
.result-msg.mid{ background:var(--surface-2); color:var(--text-muted); }
@keyframes fadeIn{ from{ opacity:0; transform:translateY(4px); } to{ opacity:1; transform:translateY(0); } }

.weak-panel{
  margin-top:16px; padding-top:16px; border-top:1px dashed var(--border);
  animation:fadeIn .3s ease;
}
.weak-head{ display:flex; align-items:center; justify-content:space-between; gap:10px; flex-wrap:wrap; margin-bottom:10px; }
.weak-title{ font-size:13px; font-weight:600; color:var(--text-muted); }
.btn.ghost.small{ padding:7px 12px; font-size:12.5px; }
.weak-list{ display:flex; flex-direction:column; gap:6px; }
.weak-row{
  display:flex; align-items:center; justify-content:space-between; gap:10px;
  background:var(--surface-2); border:1px solid var(--border);
  border-radius:8px; padding:8px 12px; font-size:12.5px;
}
.weak-row .wr-name{ font-weight:500; }
.weak-row .wr-pct{ font-family:"IBM Plex Mono",monospace; color:var(--error); font-weight:600; white-space:nowrap; }

.ref-card{ margin-top:16px; }
.ref-title{ font-size:14px; margin-bottom:12px; }
.ref-grid{ display:grid; grid-template-columns:repeat(auto-fit,minmax(130px,1fr)); gap:10px; }
.ref-item{
  display:flex; flex-direction:column; gap:3px;
  background:var(--surface-2); border:1px solid var(--border);
  border-radius:9px; padding:10px 12px;
}
.ref-proto{ font-family:"IBM Plex Mono",monospace; font-size:11px; color:var(--accent); font-weight:600; letter-spacing:.03em; }
.ref-size{ font-size:13px; font-weight:600; }

[hidden]{ display:none !important; }

@media (prefers-reduced-motion: reduce){
  *{ animation-duration:.01ms !important; animation-iteration-count:1 !important; transition-duration:.01ms !important; }
}

@media (max-width:480px){
  .top h1{ font-size:21px; }
  .field{ min-width:52px; padding:7px 4px 6px; }
  .field .f-label{ font-size:10.5px; }
}