/* =====================================================================
   NephroQBank — World-Class Nephrology Question Bank
   Design system: "Clinical Atlas"
   Typography: Inter (UI) + Newsreader (clinical stems)
   ===================================================================== */

:root {
  /* ---- Brand & semantic palette ---- */
  --teal-50:#ecfeff; --teal-100:#cffafe; --teal-300:#67e8f9; --teal-400:#22d3ee;
  --teal-500:#06b6d4; --teal-600:#0891b2; --teal-700:#0e7490; --teal-800:#155e75; --teal-900:#164e63;
  --indigo-500:#6366f1; --indigo-600:#4f46e5; --indigo-700:#4338ca;
  --emerald-400:#34d399; --emerald-500:#10b981; --emerald-600:#059669; --emerald-700:#047857;
  --rose-400:#fb7185; --rose-500:#f43f5e; --rose-600:#e11d48; --rose-700:#be123c;
  --amber-400:#fbbf24; --amber-500:#f59e0b; --amber-600:#d97706;
  --violet-400:#a78bfa; --violet-500:#8b5cf6; --violet-600:#7c3aed;
  --blue-500:#3b82f6; --blue-600:#2563eb;

  /* ---- Difficulty tiers ---- */
  --tier-basic:#0d9488; --tier-basic-bg:#ccfbf1;
  --tier-intermediate:#d97706; --tier-intermediate-bg:#fef3c7;
  --tier-advanced:#7c3aed; --tier-advanced-bg:#ede9fe;

  /* ---- Light theme (default) ---- */
  --bg: #f6f8fb;
  --bg-grad-1:#eef4f8; --bg-grad-2:#f7f9fc;
  --surface:#ffffff;
  --surface-2:#f9fbfd;
  --surface-3:#eef2f7;
  --border:#e3e9f0;
  --border-strong:#cdd7e3;
  --ink:#0f1b2d;
  --ink-2:#33445c;
  --ink-3:#5d6e85;
  --ink-faint:#8a99ac;
  --accent:var(--teal-600);
  --accent-strong:var(--teal-700);
  --accent-soft:var(--teal-50);
  --ring: rgba(8,145,178,.28);
  --shadow-sm: 0 1px 2px rgba(16,30,54,.06), 0 1px 3px rgba(16,30,54,.05);
  --shadow-md: 0 4px 14px rgba(16,30,54,.08), 0 2px 6px rgba(16,30,54,.05);
  --shadow-lg: 0 18px 40px rgba(16,30,54,.14), 0 6px 16px rgba(16,30,54,.08);
  --shadow-xl: 0 30px 60px rgba(16,30,54,.18);

  --radius-sm:9px; --radius:14px; --radius-lg:20px; --radius-xl:28px;
  --maxw: 1180px;
  --font-ui:'Inter',system-ui,-apple-system,'Segoe UI',Roboto,sans-serif;
  --font-serif:'Newsreader','Iowan Old Style','Palatino Linotype',Georgia,serif;
  --speed:.22s;
}

[data-theme="dark"] {
  --bg:#0a1018;
  --bg-grad-1:#0c1622; --bg-grad-2:#0a0f17;
  --surface:#111a26;
  --surface-2:#0f1822;
  --surface-3:#18242f;
  --border:#1e2c3a;
  --border-strong:#2b3d4f;
  --ink:#eaf1f8;
  --ink-2:#bcccdc;
  --ink-3:#8da3ba;
  --ink-faint:#62788f;
  --accent:var(--teal-400);
  --accent-strong:var(--teal-300);
  --accent-soft:rgba(34,211,238,.10);
  --ring: rgba(34,211,238,.30);
  --shadow-sm: 0 1px 2px rgba(0,0,0,.4);
  --shadow-md: 0 6px 18px rgba(0,0,0,.45);
  --shadow-lg: 0 22px 50px rgba(0,0,0,.55);
  --shadow-xl: 0 30px 70px rgba(0,0,0,.6);
  --tier-basic-bg:rgba(13,148,136,.16);
  --tier-intermediate-bg:rgba(217,119,6,.16);
  --tier-advanced-bg:rgba(124,58,237,.18);
}

/* ---------------------------------------------------------------- base */
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0; font-family:var(--font-ui); color:var(--ink);
  background:
    radial-gradient(1200px 700px at 12% -8%, var(--accent-soft), transparent 55%),
    radial-gradient(1000px 620px at 105% 0%, rgba(99,102,241,.07), transparent 50%),
    linear-gradient(180deg,var(--bg-grad-1),var(--bg-grad-2));
  background-attachment:fixed;
  line-height:1.55; -webkit-font-smoothing:antialiased; text-rendering:optimizeLegibility;
  transition:background var(--speed), color var(--speed);
}
a{color:var(--accent-strong);text-decoration:none}
button{font-family:inherit;cursor:pointer}
::selection{background:var(--teal-300);color:#04222b}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 22px}
.hidden{display:none!important}

/* scrollbar */
::-webkit-scrollbar{width:11px;height:11px}
::-webkit-scrollbar-thumb{background:var(--border-strong);border-radius:20px;border:3px solid transparent;background-clip:content-box}
::-webkit-scrollbar-thumb:hover{background:var(--ink-faint)}

/* ---------------------------------------------------------------- header */
.topbar{
  position:sticky;top:0;z-index:50;
  backdrop-filter:saturate(150%) blur(14px);
  background:color-mix(in srgb, var(--surface) 82%, transparent);
  border-bottom:1px solid var(--border);
}
.topbar-inner{display:flex;align-items:center;gap:16px;height:64px}
.brand{display:flex;align-items:center;gap:12px;cursor:pointer;user-select:none}
.brand-mark{
  width:38px;height:38px;border-radius:11px;display:grid;place-items:center;color:#fff;
  background:linear-gradient(135deg,var(--teal-500),var(--teal-700));
  box-shadow:0 6px 16px rgba(8,145,178,.4);font-size:20px;flex:none;
}
.brand-txt b{font-weight:800;letter-spacing:-.02em;font-size:1.08rem;display:block;line-height:1.1}
.brand-txt span{font-size:.72rem;color:var(--ink-3);letter-spacing:.06em;text-transform:uppercase;font-weight:600}
.topbar-spacer{flex:1}
.iconbtn{
  width:40px;height:40px;border-radius:11px;border:1px solid var(--border);
  background:var(--surface);color:var(--ink-2);display:grid;place-items:center;
  transition:var(--speed);box-shadow:var(--shadow-sm)
}
.iconbtn:hover{color:var(--accent-strong);border-color:var(--border-strong);transform:translateY(-1px)}
.iconbtn:disabled{cursor:not-allowed;opacity:.38;transform:none}
.qbank-text-size{display:inline-flex;align-items:center;gap:5px}
.qbank-text-size .iconbtn{font-size:.75rem;font-weight:800}
.ghostbtn{
  padding:9px 15px;border-radius:11px;border:1px solid var(--border);background:var(--surface);
  color:var(--ink-2);font-weight:600;font-size:.86rem;display:inline-flex;align-items:center;gap:7px;
  transition:var(--speed);box-shadow:var(--shadow-sm)
}
.ghostbtn:hover{color:var(--accent-strong);border-color:var(--border-strong)}

/* ---------------------------------------------------------------- hero */
.hero{padding:54px 0 30px;position:relative}
.eyebrow{
  display:inline-flex;align-items:center;gap:8px;font-size:.74rem;font-weight:700;letter-spacing:.13em;
  text-transform:uppercase;color:var(--accent-strong);background:var(--accent-soft);
  padding:7px 14px;border-radius:999px;border:1px solid color-mix(in srgb,var(--accent) 25%,transparent)
}
.hero h1{
  font-family:var(--font-serif);font-weight:600;letter-spacing:-.02em;
  font-size:clamp(2.1rem,4.6vw,3.5rem);line-height:1.06;margin:18px 0 14px;color:var(--ink)
}
.hero h1 em{font-style:italic;color:var(--accent-strong)}
.hero p.lead{font-size:clamp(1rem,1.6vw,1.18rem);color:var(--ink-2);max-width:680px;margin:0 0 26px}
.hero-stats{display:flex;flex-wrap:wrap;gap:14px;margin-top:8px}
.stat{
  background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);
  padding:14px 20px;min-width:118px;box-shadow:var(--shadow-sm)
}
.stat b{display:block;font-size:1.65rem;font-weight:800;letter-spacing:-.02em;color:var(--ink);
  font-variant-numeric:tabular-nums}
.stat span{font-size:.76rem;color:var(--ink-3);font-weight:600;text-transform:uppercase;letter-spacing:.05em}
.stat.accent b{color:var(--accent-strong)}

/* ---------------------------------------------------------------- section heading */
.section-head{display:flex;align-items:flex-end;justify-content:space-between;gap:16px;margin:42px 0 20px}
.section-head h2{font-size:1.5rem;font-weight:800;letter-spacing:-.02em;margin:0;color:var(--ink)}
.section-head p{margin:4px 0 0;color:var(--ink-3);font-size:.92rem}

/* ---------------------------------------------------------------- chapter grid */
.chips{display:flex;flex-wrap:wrap;gap:9px;margin-bottom:8px}
.chip{
  font-size:.78rem;font-weight:600;padding:7px 13px;border-radius:999px;border:1px solid var(--border);
  background:var(--surface);color:var(--ink-2);transition:var(--speed)
}
.chip:hover{border-color:var(--border-strong);color:var(--ink)}
.chip.active{background:var(--accent);color:#fff;border-color:var(--accent)}

.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(330px,1fr));gap:20px}
.ch-card{
  position:relative;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-lg);
  padding:22px 22px 20px;box-shadow:var(--shadow-sm);overflow:hidden;cursor:pointer;
  transition:transform var(--speed), box-shadow var(--speed), border-color var(--speed);
  display:flex;flex-direction:column;min-height:212px
}
.ch-card::before{
  content:"";position:absolute;inset:0 0 auto 0;height:4px;
  background:linear-gradient(90deg,var(--cc1,var(--teal-500)),var(--cc2,var(--indigo-500)))
}
.ch-card:hover{transform:translateY(-4px);box-shadow:var(--shadow-lg);border-color:var(--border-strong)}
.ch-top{display:flex;align-items:flex-start;gap:14px;margin-bottom:12px}
.ch-icon{
  width:50px;height:50px;border-radius:14px;display:grid;place-items:center;font-size:25px;flex:none;
  background:linear-gradient(135deg,color-mix(in srgb,var(--cc1,var(--teal-500)) 22%,var(--surface)),color-mix(in srgb,var(--cc2,var(--indigo-500)) 16%,var(--surface)));
  border:1px solid var(--border)
}
.ch-num{font-size:.72rem;font-weight:800;color:var(--ink-faint);letter-spacing:.08em}
.ch-card h3{font-size:1.16rem;font-weight:800;letter-spacing:-.02em;margin:2px 0 0;color:var(--ink);line-height:1.2}
.ch-desc{font-size:.88rem;color:var(--ink-3);margin:0 0 14px;flex:1}
.ch-meta{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-top:auto}
.ch-qcount{font-size:.82rem;font-weight:700;color:var(--ink-2)}
.ch-qcount svg{vertical-align:-2px;margin-right:5px;color:var(--accent)}
.ch-progress{flex:1;height:7px;border-radius:99px;background:var(--surface-3);overflow:hidden;max-width:120px}
.ch-progress > i{display:block;height:100%;border-radius:99px;background:linear-gradient(90deg,var(--emerald-400),var(--emerald-600));width:0%}
.ch-pct{font-size:.76rem;font-weight:700;color:var(--ink-3);font-variant-numeric:tabular-nums;min-width:34px;text-align:right}
.tier-dots{display:flex;gap:5px;margin-top:11px}
.tier-dot{display:inline-flex;align-items:center;gap:5px;font-size:.68rem;font-weight:700;color:var(--ink-3)}
.tier-dot i{width:8px;height:8px;border-radius:99px;display:inline-block}

.ch-card.locked{opacity:.6;cursor:default}
.ch-card.locked:hover{transform:none;box-shadow:var(--shadow-sm)}
.soon-tag{position:absolute;top:14px;right:14px;font-size:.66rem;font-weight:800;letter-spacing:.08em;
  text-transform:uppercase;color:var(--ink-faint);background:var(--surface-3);padding:4px 9px;border-radius:99px}

/* ---------------------------------------------------------------- chapter detail / mode picker */
.detail-hero{
  background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-xl);
  padding:30px;box-shadow:var(--shadow-md);position:relative;overflow:hidden;margin-bottom:24px
}
.detail-hero::after{content:"";position:absolute;top:-60px;right:-40px;width:260px;height:260px;border-radius:50%;
  background:radial-gradient(circle,var(--accent-soft),transparent 70%);pointer-events:none}
.crumb{display:inline-flex;align-items:center;gap:7px;font-size:.84rem;font-weight:600;color:var(--ink-3);
  background:var(--surface-2);border:1px solid var(--border);padding:7px 13px;border-radius:99px;margin-bottom:16px;cursor:pointer}
.crumb:hover{color:var(--accent-strong)}
.ch-card[role="button"]:focus-visible,.mode-card[role="button"]:focus-visible,.crumb:focus-visible{outline:3px solid var(--accent);outline-offset:4px}
.detail-hero h1{font-family:var(--font-serif);font-weight:600;font-size:clamp(1.7rem,3.4vw,2.5rem);margin:0 0 8px;letter-spacing:-.02em}
.detail-hero p{color:var(--ink-2);max-width:680px;margin:0;font-size:1rem}

.modes{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:16px;margin-bottom:18px}
.qbank-continue{display:flex;align-items:center;justify-content:space-between;gap:20px;margin-top:28px;padding:20px 22px;border:1px solid var(--border-strong);border-left:5px solid var(--accent);border-radius:var(--radius-sm);background:var(--surface);box-shadow:var(--shadow-sm)}
.qbank-continue div{display:grid;gap:4px}.qbank-continue span{color:var(--accent-strong);font-size:.72rem;font-weight:800;letter-spacing:.1em;text-transform:uppercase}.qbank-continue strong{font-family:var(--font-serif);font-size:1.25rem}.qbank-continue small{color:var(--ink-3)}
.mode-card{
  background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:18px 18px;
  box-shadow:var(--shadow-sm);cursor:pointer;transition:var(--speed);display:flex;gap:14px;align-items:flex-start
}
.mode-card:hover{transform:translateY(-3px);box-shadow:var(--shadow-md);border-color:var(--accent)}
.mode-card.mode-disabled{cursor:not-allowed;opacity:.52}.mode-card.mode-disabled:hover{transform:none;box-shadow:none;border-color:var(--border)}
.mode-ic{width:42px;height:42px;border-radius:11px;display:grid;place-items:center;font-size:20px;flex:none;
  background:var(--accent-soft);color:var(--accent-strong);border:1px solid color-mix(in srgb,var(--accent) 22%,transparent)}
.mode-card h4{margin:0 0 3px;font-size:1rem;font-weight:800;letter-spacing:-.01em}
.mode-card p{margin:0;font-size:.83rem;color:var(--ink-3)}

.filters{display:flex;flex-wrap:wrap;gap:10px;align-items:center;background:var(--surface);
  border:1px solid var(--border);border-radius:var(--radius);padding:14px 16px;box-shadow:var(--shadow-sm)}
.filters .fl-label{font-size:.78rem;font-weight:700;color:var(--ink-3);text-transform:uppercase;letter-spacing:.05em}

/* ---------------------------------------------------------------- quiz */
.quiz-wrap{max-width:840px;margin:0 auto}
.quiz-bar{display:flex;align-items:center;gap:14px;margin:8px 0 18px}
.quiz-bar .qprog{flex:1;height:9px;border-radius:99px;background:var(--surface-3);overflow:hidden;box-shadow:inset 0 1px 2px rgba(0,0,0,.06)}
.quiz-bar .qprog > i{display:block;height:100%;background:linear-gradient(90deg,var(--teal-400),var(--teal-600));border-radius:99px;transition:width .4s cubic-bezier(.4,0,.2,1)}
.quiz-bar .qcount{font-size:.86rem;font-weight:700;color:var(--ink-2);font-variant-numeric:tabular-nums;white-space:nowrap}
.quiz-bar .qtimer{font-size:.86rem;font-weight:700;color:var(--ink-2);font-variant-numeric:tabular-nums;
  background:var(--surface);border:1px solid var(--border);padding:6px 12px;border-radius:99px;box-shadow:var(--shadow-sm)}

.card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-lg);
  box-shadow:var(--shadow-md);overflow:hidden}
.card-pad{padding:26px 30px}
@media(max-width:620px){.card-pad{padding:20px 18px}}

.q-badges{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:16px}
.badge{font-size:.7rem;font-weight:800;letter-spacing:.04em;text-transform:uppercase;
  padding:5px 11px;border-radius:99px;display:inline-flex;align-items:center;gap:6px}
.badge.b-basic{color:var(--tier-basic);background:var(--tier-basic-bg)}
.badge.b-intermediate{color:var(--tier-intermediate);background:var(--tier-intermediate-bg)}
.badge.b-advanced{color:var(--tier-advanced);background:var(--tier-advanced-bg)}
.badge.b-type{color:var(--ink-2);background:var(--surface-3)}
.badge.b-tag{color:var(--accent-strong);background:var(--accent-soft);text-transform:none;letter-spacing:0;font-weight:700}

.case-vignette{
  background:linear-gradient(180deg,var(--surface-2),var(--surface));
  border:1px solid var(--border);border-left:4px solid var(--accent);
  border-radius:var(--radius);padding:18px 20px;margin-bottom:20px
}
.case-vignette .cv-label{font-size:.72rem;font-weight:800;letter-spacing:.1em;text-transform:uppercase;
  color:var(--accent-strong);margin-bottom:8px;display:flex;align-items:center;gap:7px}
.case-vignette p{margin:0 0 10px;font-family:var(--font-serif);font-size:1.04rem;color:var(--ink);line-height:1.6}
.case-vignette p:last-child{margin-bottom:0}
.labs{display:grid;grid-template-columns:repeat(auto-fill,minmax(150px,1fr));gap:8px;margin-top:12px}
.lab{background:var(--surface);border:1px solid var(--border);border-radius:10px;padding:8px 11px}
.lab .ln{font-size:.7rem;font-weight:700;color:var(--ink-3);text-transform:uppercase;letter-spacing:.04em}
.lab .lv{font-size:.96rem;font-weight:800;color:var(--ink);font-variant-numeric:tabular-nums}
.lab.hi .lv{color:var(--rose-600)} .lab.lo .lv{color:var(--blue-600)} .lab.ok .lv{color:var(--emerald-600)}

.q-stem{font-family:var(--font-serif);font-size:1.22rem;line-height:1.55;color:var(--ink);margin:0 0 22px;font-weight:500}
.case-part-no{font-size:.74rem;font-weight:800;letter-spacing:.08em;text-transform:uppercase;color:var(--accent-strong);margin-bottom:6px}

.options{display:flex;flex-direction:column;gap:11px}
.opt{
  display:flex;gap:14px;align-items:flex-start;text-align:left;width:100%;
  background:var(--surface);border:1.5px solid var(--border);border-radius:var(--radius);
  padding:15px 17px;transition:var(--speed);color:var(--ink);font-size:1rem;line-height:1.45
}
.opt:hover:not(:disabled){border-color:var(--accent);background:var(--accent-soft);transform:translateY(-1px)}
.opt:disabled{cursor:default}
.opt .key{
  width:30px;height:30px;border-radius:9px;flex:none;display:grid;place-items:center;font-weight:800;font-size:.92rem;
  background:var(--surface-3);color:var(--ink-2);border:1px solid var(--border);transition:var(--speed)
}
.opt .otext{flex:1;padding-top:2px}
.opt.selected{border-color:var(--accent);background:var(--accent-soft)}
.opt.selected .key{background:var(--accent);color:#fff;border-color:var(--accent)}
.opt.correct{border-color:var(--emerald-500);background:color-mix(in srgb,var(--emerald-500) 12%,var(--surface))}
.opt.correct .key{background:var(--emerald-500);color:#fff;border-color:var(--emerald-500)}
.opt.incorrect{border-color:var(--rose-500);background:color-mix(in srgb,var(--rose-500) 11%,var(--surface))}
.opt.incorrect .key{background:var(--rose-500);color:#fff;border-color:var(--rose-500)}
.opt .mark{margin-left:auto;font-weight:800;font-size:1.1rem;align-self:center;opacity:0;transition:var(--speed)}
.opt.correct .mark{opacity:1;color:var(--emerald-600)}
.opt.incorrect .mark{opacity:1;color:var(--rose-600)}

/* ---------------------------------------------------------------- explanation */
.explain{margin-top:22px;border-radius:var(--radius);overflow:hidden;border:1px solid var(--border);
  animation:slideIn .4s cubic-bezier(.16,1,.3,1)}
@keyframes slideIn{from{opacity:0;transform:translateY(10px)}to{opacity:1;transform:none}}
.verdict{display:flex;align-items:center;gap:12px;padding:15px 20px;font-weight:800;font-size:1.02rem}
.verdict.right{background:color-mix(in srgb,var(--emerald-500) 14%,var(--surface));color:var(--emerald-700)}
.verdict.wrong{background:color-mix(in srgb,var(--rose-500) 13%,var(--surface));color:var(--rose-700)}
.verdict .vic{width:30px;height:30px;border-radius:50%;display:grid;place-items:center;color:#fff;font-size:1rem;flex:none}
.verdict.right .vic{background:var(--emerald-500)} .verdict.wrong .vic{background:var(--rose-500)}
.verdict .ans-key{margin-left:auto;font-size:.82rem;font-weight:700;opacity:.85}
.explain-body{background:var(--surface);padding:22px 22px}
.ex-block{margin-bottom:18px}
.ex-block:last-child{margin-bottom:0}
.ex-h{display:flex;align-items:center;gap:8px;font-size:.76rem;font-weight:800;letter-spacing:.08em;
  text-transform:uppercase;color:var(--ink-3);margin-bottom:8px}
.ex-h .dot{width:7px;height:7px;border-radius:50%;background:var(--accent)}
.ex-block p{margin:0;color:var(--ink-2);font-size:.97rem;line-height:1.65}
.ex-block.correct-why{background:color-mix(in srgb,var(--emerald-500) 7%,var(--surface));
  border:1px solid color-mix(in srgb,var(--emerald-500) 25%,transparent);border-radius:var(--radius-sm);padding:14px 16px}
.ex-block.correct-why .ex-h{color:var(--emerald-700)} .ex-block.correct-why .dot{background:var(--emerald-500)}
.opt-breakdown{display:flex;flex-direction:column;gap:8px}
.ob{display:flex;gap:11px;align-items:flex-start;font-size:.92rem;padding:10px 12px;border-radius:10px;background:var(--surface-2);border:1px solid var(--border)}
.ob .obk{width:24px;height:24px;border-radius:7px;flex:none;display:grid;place-items:center;font-weight:800;font-size:.8rem;color:#fff}
.ob.r .obk{background:var(--emerald-500)} .ob.w .obk{background:var(--rose-400)}
.ob .obt{flex:1;color:var(--ink-2)} .ob .obt b{color:var(--ink)}
.pearl{background:linear-gradient(135deg,color-mix(in srgb,var(--amber-500) 11%,var(--surface)),var(--surface));
  border:1px solid color-mix(in srgb,var(--amber-500) 32%,transparent);border-radius:var(--radius-sm);padding:14px 16px}
.pearl .ex-h{color:var(--amber-600)} .pearl .dot{background:var(--amber-500)}
.ref{font-size:.83rem;color:var(--ink-faint);display:flex;align-items:flex-start;gap:8px;margin-top:4px;
  padding-top:14px;border-top:1px dashed var(--border)}
.ref svg{flex:none;margin-top:2px;color:var(--ink-faint)}
.ref b{color:var(--ink-3);font-weight:700}

/* ---------------------------------------------------------------- quiz footer nav */
.quiz-nav{display:flex;align-items:center;gap:12px;margin-top:22px}
.btn{
  padding:13px 22px;border-radius:13px;border:1px solid transparent;font-weight:700;font-size:.95rem;
  display:inline-flex;align-items:center;gap:9px;transition:var(--speed);box-shadow:var(--shadow-sm)
}
.btn-primary{background:linear-gradient(135deg,var(--teal-500),var(--teal-700));color:#fff;border:none;box-shadow:0 8px 20px rgba(8,145,178,.32)}
.btn-primary:hover{transform:translateY(-2px);box-shadow:0 12px 26px rgba(8,145,178,.4)}
.btn-primary:disabled{opacity:.45;transform:none;box-shadow:none;cursor:not-allowed}
.btn-ghost{background:var(--surface);border:1px solid var(--border);color:var(--ink-2)}
.btn-ghost:hover{border-color:var(--border-strong);color:var(--ink)}
.btn-ghost:disabled{opacity:.4;cursor:not-allowed}
.flagbtn{margin-left:auto;background:var(--surface);border:1px solid var(--border);color:var(--ink-3);
  padding:11px 15px;border-radius:12px;font-weight:600;font-size:.86rem;display:inline-flex;gap:8px;align-items:center;transition:var(--speed)}
.flagbtn:hover{color:var(--amber-600);border-color:var(--amber-500)}
.flagbtn.on{color:var(--amber-600);background:color-mix(in srgb,var(--amber-500) 12%,var(--surface));border-color:var(--amber-500)}

/* ---------------------------------------------------------------- results */
.results{max-width:760px;margin:0 auto;text-align:center}
.score-ring{width:200px;height:200px;margin:10px auto 18px;position:relative}
.score-ring svg{transform:rotate(-90deg)}
.score-ring .sc-num{position:absolute;inset:0;display:grid;place-content:center;text-align:center}
.score-ring .sc-num b{font-size:3rem;font-weight:800;letter-spacing:-.03em;line-height:1;color:var(--ink);font-variant-numeric:tabular-nums}
.score-ring .sc-num span{font-size:.8rem;color:var(--ink-3);font-weight:700;text-transform:uppercase;letter-spacing:.06em}
.res-title{font-family:var(--font-serif);font-size:2rem;font-weight:600;margin:0 0 6px}
.res-sub{color:var(--ink-3);margin:0 0 26px}
.res-stats{display:grid;grid-template-columns:repeat(3,1fr);gap:14px;margin-bottom:26px}
.res-stat{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:18px;box-shadow:var(--shadow-sm)}
.res-stat b{display:block;font-size:1.8rem;font-weight:800;font-variant-numeric:tabular-nums}
.res-stat span{font-size:.78rem;color:var(--ink-3);font-weight:600;text-transform:uppercase;letter-spacing:.04em}
.res-stat.good b{color:var(--emerald-600)} .res-stat.bad b{color:var(--rose-600)} .res-stat.flag b{color:var(--amber-600)}
.res-actions{display:flex;gap:12px;justify-content:center;flex-wrap:wrap}

.review-list{margin-top:30px;text-align:left}
.review-item{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);
  padding:16px 18px;margin-bottom:10px;display:flex;gap:13px;align-items:flex-start;cursor:pointer;transition:var(--speed)}
.review-item:hover{border-color:var(--border-strong);box-shadow:var(--shadow-sm)}
.review-item .ri-ic{width:26px;height:26px;border-radius:8px;flex:none;display:grid;place-items:center;color:#fff;font-weight:800;font-size:.82rem}
.review-item.r .ri-ic{background:var(--emerald-500)} .review-item.w .ri-ic{background:var(--rose-500)}
.review-item .ri-q{flex:1;font-size:.92rem;color:var(--ink-2)}
.review-item .ri-q b{color:var(--ink);display:block;font-size:.78rem;margin-bottom:2px;text-transform:uppercase;letter-spacing:.04em;color:var(--ink-faint)}

/* ---------------------------------------------------------------- footer */
.footer{margin-top:60px;border-top:1px solid var(--border);padding:28px 0 50px;color:var(--ink-faint);font-size:.85rem}
.footer .wrap{display:flex;flex-wrap:wrap;gap:14px;align-items:center;justify-content:space-between}
.footer b{color:var(--ink-3)}

/* select */
.sel{appearance:none;background:var(--surface);border:1px solid var(--border);border-radius:10px;
  padding:8px 32px 8px 12px;font-weight:600;font-size:.85rem;color:var(--ink-2);box-shadow:var(--shadow-sm);
  background-image:url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='14' height='14' viewBox='0 0 24 24' fill='none' stroke='%235d6e85' stroke-width='2.5'><path d='M6 9l6 6 6-6'/></svg>");
  background-repeat:no-repeat;background-position:right 10px center}
.sel:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px var(--ring)}

.empty{text-align:center;padding:70px 20px;color:var(--ink-3)}
.empty .ei{font-size:3rem;margin-bottom:10px}

.toast{position:fixed;bottom:24px;left:50%;transform:translateX(-50%) translateY(20px);opacity:0;
  background:var(--ink);color:#fff;padding:12px 20px;border-radius:12px;font-weight:600;font-size:.88rem;
  box-shadow:var(--shadow-lg);z-index:100;transition:var(--speed);pointer-events:none}
.toast.show{opacity:1;transform:translateX(-50%) translateY(0)}

@media(max-width:620px){
  .hero{padding:34px 0 18px}
  .res-stats{grid-template-columns:1fr}
  .quiz-nav{flex-wrap:wrap}
  .quiz-nav .btn{flex:1;justify-content:center}
}
.fade-in{animation:fadeIn .35s ease}
@keyframes fadeIn{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:none}}

/* =====================================================================
   NephroZayan editorial refinement — 2026
   Keeps the quiz engine intact while giving the library a clinical,
   scholarly rhythm inspired by a modern reference atlas.
   ===================================================================== */
body{
  background:linear-gradient(180deg,#eef7fa 0,#f8fbfd 520px,var(--bg) 900px);
}
[data-theme="dark"] body{
  background:linear-gradient(180deg,#0b1721 0,#0a1119 620px,var(--bg) 1000px);
}
.wrap{max-width:1240px;padding-inline:28px}
.topbar{background:color-mix(in srgb,var(--surface) 94%,transparent)}
.topbar-inner{height:76px;gap:22px}
.brand{gap:11px;min-width:max-content}
.brand-mark{
  width:52px;height:44px;border:0;border-radius:0;object-fit:contain;
  background:transparent;box-shadow:none;font-size:0;
}
.brand-txt b{font-family:var(--font-serif);font-size:1.2rem;font-weight:600;color:var(--ink)}
.brand-txt span{font-size:.63rem;letter-spacing:.12em}
.site-link{
  display:inline-flex;align-items:center;gap:8px;padding-left:22px;margin-left:4px;
  border-left:1px solid var(--border-strong);font-size:.82rem;font-weight:700;color:var(--accent-strong)
}
.site-link:hover{color:var(--ink)}
.hero{padding:58px 0 52px;border-bottom:1px solid var(--border);background:rgba(255,255,255,.22)}
.hero-grid{display:grid;grid-template-columns:minmax(0,1fr) minmax(520px,.95fr);gap:68px;align-items:end}
.hero-copy{max-width:640px}
.hero .product-name{
  margin:0 0 20px;font-family:var(--font-serif);font-style:normal;font-size:clamp(3.3rem,6vw,5.6rem);
  line-height:.92;font-weight:500;letter-spacing:-.055em;color:var(--navy,#0c2343)
}
.hero h2{
  margin:0 0 16px;font-family:var(--font-serif);font-size:clamp(1.85rem,3.2vw,3rem);
  line-height:1.08;font-weight:500;letter-spacing:-.025em;color:var(--ink)
}
.hero p.lead{font-size:1.02rem;line-height:1.7;margin:0;max-width:610px}
.hero-stats{
  display:grid;grid-template-columns:repeat(4,1fr);gap:0;margin:0;background:var(--surface);
  border:1px solid var(--border-strong);border-radius:var(--radius-sm);box-shadow:var(--shadow-md);overflow:hidden
}
.stat{min-width:0;padding:25px 18px;text-align:center;border:0;border-right:1px solid var(--border);border-radius:0;box-shadow:none}
.stat:last-child{border-right:0}
.stat b{font-family:var(--font-serif);font-size:2.35rem;font-weight:500;color:var(--ink)}
.stat.accent b{color:var(--teal-700)}
.stat span{font-size:.67rem;letter-spacing:.09em}
.section-head{margin:40px 0 18px;padding-bottom:12px;border-bottom:1px solid var(--border-strong)}
.section-head h2{font-family:var(--font-serif);font-size:2rem;font-weight:500}
.grid{display:block;border-top:0;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-sm);overflow:hidden}
.ch-card{
  min-height:0;padding:20px 22px;display:grid;
  grid-template-columns:minmax(330px,1.55fr) minmax(190px,.72fr) minmax(340px,1fr);
  grid-template-areas:"top tiers meta" "desc tiers meta";gap:3px 28px;align-items:center;
  border:0;border-bottom:1px solid var(--border);border-radius:0;box-shadow:none;overflow:visible
}
.ch-card:last-child{border-bottom:0}
.ch-card::before{inset:0 auto 0 0;width:3px;height:auto;background:var(--cc1,var(--teal-600));opacity:.7}
.ch-card:hover{transform:none;background:var(--surface-2);border-color:var(--border);box-shadow:none}
.ch-card:hover::before{width:5px;opacity:1}
.ch-top{grid-area:top;align-items:center;margin:0}
.ch-icon{
  width:52px;height:52px;border-radius:50%;font-family:var(--font-serif);font-size:1.05rem;font-weight:600;
  color:var(--cc1,var(--teal-700));background:color-mix(in srgb,var(--cc1,var(--teal-500)) 9%,var(--surface));
  border-color:color-mix(in srgb,var(--cc1,var(--teal-500)) 24%,var(--border))
}
.ch-num{font-size:.63rem;letter-spacing:.11em}
.ch-card h3{font-family:var(--font-serif);font-size:1.28rem;font-weight:600;letter-spacing:-.012em}
.ch-desc{grid-area:desc;margin:2px 0 0;padding-left:66px;font-size:.82rem;line-height:1.5}
.tier-dots{grid-area:tiers;display:flex;flex-direction:column;gap:5px;margin:0}
.tier-dot{font-size:.7rem;text-transform:capitalize}
.ch-meta{grid-area:meta;display:grid;grid-template-columns:auto 1fr auto auto;gap:10px;align-items:center}
.ch-progress{max-width:none}
.ch-open{
  display:inline-flex;align-items:center;gap:6px;margin-left:6px;padding:9px 11px;border:1px solid var(--accent);
  border-radius:6px;color:var(--accent-strong);font-size:.74rem;font-weight:800;white-space:nowrap
}
.ch-card:hover .ch-open{background:var(--accent);color:#fff}
.detail-hero{border-radius:var(--radius);box-shadow:var(--shadow-sm)}
.mode-card{border-radius:var(--radius-sm);box-shadow:none}
.mode-ic{border-radius:8px;font-size:0}
.mode-ic svg{width:20px;height:20px}
.case-vignette .cv-label svg{width:15px;height:15px}
.card,.explain{border-radius:var(--radius-sm)}

@media(max-width:1050px){
  .hero-grid{grid-template-columns:1fr;gap:32px;align-items:start}
  .hero-copy{max-width:760px}
  .hero-stats{max-width:760px}
  .ch-card{grid-template-columns:minmax(300px,1fr) minmax(300px,.8fr);grid-template-areas:"top tiers" "desc meta"}
}
@media(max-width:760px){
  .wrap{padding-inline:18px}
  .topbar-inner{height:68px;gap:12px}
  .brand-mark{width:43px;height:36px}
  .brand-txt span{display:none}
  .site-link{margin-left:0;padding-left:12px}
  .site-link span{display:none}
  .hero{padding:38px 0 34px}
  .hero .product-name{font-size:3.35rem}
  .hero h2{font-size:1.8rem}
  .hero-stats{grid-template-columns:repeat(2,1fr)}
  .stat:nth-child(2){border-right:0}
  .stat:nth-child(-n+2){border-bottom:1px solid var(--border)}
  .ch-card{grid-template-columns:1fr;grid-template-areas:"top" "desc" "tiers" "meta";gap:10px;padding:19px 17px}
  .ch-desc{padding-left:0}
  .tier-dots{flex-direction:row;flex-wrap:wrap}
  .ch-meta{grid-template-columns:auto 1fr auto}
  .ch-open{grid-column:1/-1;justify-content:center;margin:4px 0 0}
  .qbank-continue{align-items:stretch;flex-direction:column}.qbank-continue .btn{width:100%}
}
@media(max-width:430px){
  .brand-txt{display:none}
  .qbank-text-size{gap:3px}.qbank-text-size .iconbtn{width:38px;height:38px}
  .hero .product-name{font-size:2.85rem}
  .stat{padding:18px 10px}.stat b{font-size:1.9rem}
}
.fade-in{animation:none;opacity:1}
@media(prefers-reduced-motion:reduce){
  *,*::before,*::after{scroll-behavior:auto!important;transition-duration:.01ms!important;animation-duration:.01ms!important;animation-iteration-count:1!important}
}