/* ===================================================================
   MK MathLab — Quiz Center · "Mint Pop" theme (LOCKED, §5)
   Dark bg #0e1116 · surface #171d26 · ink #f3f7fb · muted #8b97a6
   Mint #5ee6a8 (brand/correct) · Coral #ff8fa3 (wrong) · Butter #ffe066
   Fonts: Fredoka (display) + Lexend (body/math UI)
   Perky pass: springy buttons, animated cards, soft glows, confetti.
   =================================================================== */

:root{
  --bg:#0e1116;
  --surface:#171d26;
  --surface-2:#1e2632;
  --ink:#f3f7fb;
  --muted:#8b97a6;
  --mint:#5ee6a8;
  --mint-dk:#062418;
  --coral:#ff8fa3;
  --coral-dk:#2a0010;
  --butter:#ffe066;
  --line:#2a3340;
  --radius:18px;
  --shadow:0 10px 30px rgba(0,0,0,.35);
  --spring:cubic-bezier(.34,1.56,.64,1);   /* overshoot = perky */
  --display:"Fredoka",system-ui,sans-serif;
  --body:"Lexend",system-ui,sans-serif;
}

*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  background:var(--bg);
  color:var(--ink);
  font-family:var(--body);
  line-height:1.55;
  -webkit-font-smoothing:antialiased;
  min-height:100vh;
  overflow-x:hidden;
}

/* soft decorative glows in the page corners (depth, never behind equations) */
body::before,body::after{
  content:"";position:fixed;border-radius:50%;filter:blur(75px);z-index:-1;pointer-events:none;
}
body::before{top:-120px;left:-90px;width:320px;height:320px;background:var(--mint);opacity:.15}
body::after{bottom:-140px;right:-100px;width:340px;height:340px;background:var(--coral);opacity:.12}

.gridband{
  background-image:
    linear-gradient(rgba(94,230,168,.05) 1px,transparent 1px),
    linear-gradient(90deg,rgba(94,230,168,.05) 1px,transparent 1px);
  background-size:26px 26px;
}

.wrap{max-width:760px;margin:0 auto;padding:28px 20px 64px;position:relative}

/* ---------- header / brand ---------- */
.brand{display:flex;align-items:center;gap:12px;margin-bottom:6px}
.brand .logo{
  width:42px;height:42px;border-radius:12px;flex:0 0 auto;
  background:linear-gradient(135deg,var(--mint),#3fcf8e);
  display:grid;place-items:center;color:#06231a;font-family:var(--display);
  font-weight:700;font-size:22px;box-shadow:var(--shadow);
  animation:logopulse 2.6s ease-in-out infinite;
}
@keyframes logopulse{0%,100%{transform:rotate(0) scale(1)}50%{transform:rotate(-4deg) scale(1.06)}}
.brand h1{
  font-family:var(--display);font-weight:600;font-size:1.5rem;
  margin:0;letter-spacing:.2px;
}
.tagline{color:var(--muted);font-size:.95rem;margin:2px 0 22px}
a{color:var(--mint);text-decoration:none}
a:hover{text-decoration:underline}

/* ---------- topic menu (index) ---------- */
.section-label{
  font-family:var(--display);font-weight:600;font-size:.8rem;
  text-transform:uppercase;letter-spacing:2px;color:var(--muted);
  margin:28px 0 12px;
}
.topics{display:flex;flex-direction:column;gap:12px}
.topic{
  display:flex;align-items:center;gap:14px;
  background:var(--surface);border:1px solid var(--line);
  border-radius:var(--radius);padding:16px 18px;
  text-decoration:none;color:var(--ink);
  transition:transform .18s var(--spring),border-color .18s,box-shadow .18s;
  animation:riseIn .5s var(--spring) both;
}
.topics .topic:nth-child(1){animation-delay:.04s}
.topics .topic:nth-child(2){animation-delay:.10s}
.topics .topic:nth-child(3){animation-delay:.16s}
.topics .topic:nth-child(4){animation-delay:.22s}
@keyframes riseIn{from{opacity:0;transform:translateY(14px) scale(.98)}to{opacity:1;transform:none}}
.topic:hover{text-decoration:none;border-color:#3a4a5e;transform:translateY(-3px) scale(1.01);box-shadow:0 12px 28px rgba(0,0,0,.3)}
.topic .ic{
  width:40px;height:40px;border-radius:11px;flex:0 0 auto;
  display:grid;place-items:center;font-size:20px;
  background:var(--surface-2);transition:transform .18s var(--spring);
}
.topic:hover .ic{transform:scale(1.1) rotate(-6deg)}
.topic .meta{flex:1 1 auto;min-width:0}
.topic .t{font-family:var(--display);font-weight:500;font-size:1.05rem}
.topic .d{color:var(--muted);font-size:.86rem;margin-top:1px}
.topic .badge{
  font-size:.7rem;font-weight:600;letter-spacing:.5px;text-transform:uppercase;
  padding:4px 9px;border-radius:999px;white-space:nowrap;
}
.badge.free{background:rgba(94,230,168,.14);color:var(--mint)}
.badge.locked{background:rgba(139,151,166,.14);color:var(--muted)}
.badge.soon{background:rgba(255,224,102,.13);color:var(--butter)}
.topic.is-locked{opacity:.82}
.topic.is-soon{opacity:.6;pointer-events:none;cursor:default;animation:none}
.topic.is-locked .ic{color:var(--muted)}

/* ---------- gate / cards ---------- */
.card{
  background:var(--surface);border:1px solid var(--line);
  border-radius:var(--radius);padding:22px;box-shadow:var(--shadow);
  animation:cardIn .42s var(--spring);
}
@keyframes cardIn{from{opacity:0;transform:translateY(14px) scale(.985)}to{opacity:1;transform:none}}
.gate h2{font-family:var(--display);font-weight:600;margin:.1rem 0 .4rem}
.gate p{color:var(--muted);margin:.3rem 0 1rem}
.gate .row{display:flex;gap:10px;flex-wrap:wrap}
.gate input[type=email]{
  flex:1 1 220px;background:var(--bg);border:1px solid var(--line);
  color:var(--ink);border-radius:12px;padding:13px 15px;font-size:1rem;
  font-family:var(--body);outline:none;transition:border-color .15s,box-shadow .15s;
}
.gate input[type=email]:focus{border-color:var(--mint);box-shadow:0 0 0 3px rgba(94,230,168,.15)}
.gate .err{color:var(--coral);font-size:.85rem;min-height:1.2em;margin-top:.5rem}
.fineprint{color:var(--muted);font-size:.78rem;margin-top:.8rem}

/* ---------- buttons ---------- */
.btn{
  font-family:var(--display);font-weight:500;font-size:1rem;
  border:none;border-radius:13px;padding:13px 20px;cursor:pointer;
  color:#06231a;
  background:linear-gradient(110deg,var(--mint) 0%,#7ff0bd 30%,var(--mint) 60%);
  background-size:220% 100%;
  box-shadow:0 8px 20px rgba(94,230,168,.24);
  transition:transform .18s var(--spring),box-shadow .18s ease;
  animation:shimmer 3.4s linear infinite;
}
@keyframes shimmer{to{background-position:-220% 0}}
.btn:hover{transform:translateY(-3px) scale(1.015);box-shadow:0 12px 28px rgba(94,230,168,.38)}
.btn:active{transform:translateY(0) scale(.96)}
.btn.ghost{background:transparent;color:var(--ink);border:1px solid var(--line);box-shadow:none;animation:none}
.btn.ghost:hover{border-color:#3a4658;transform:translateY(-2px)}
.btn[disabled]{opacity:.45;cursor:not-allowed;transform:none;box-shadow:none;animation:none}

/* ---------- quiz engine ---------- */
.quizhead{display:flex;justify-content:space-between;align-items:baseline;gap:12px;margin-bottom:6px}
.quizhead h2{font-family:var(--display);font-weight:600;font-size:1.35rem;margin:0}
.progress{color:var(--muted);font-size:.86rem;font-family:var(--display)}
.pbar{height:7px;background:var(--surface-2);border-radius:999px;overflow:hidden;margin:14px 0 22px}
.pbar > i{display:block;height:100%;background:linear-gradient(90deg,var(--mint),#3fcf8e);width:0;transition:width .4s var(--spring);box-shadow:0 0 12px rgba(94,230,168,.5)}

.q-prompt{font-size:1.02rem;margin:0 0 4px}
.q-kind{
  display:inline-block;font-family:var(--display);font-size:.7rem;font-weight:600;
  letter-spacing:1px;text-transform:uppercase;color:var(--butter);
  background:rgba(255,224,102,.1);border:1px solid var(--butter);
  border-radius:999px;padding:3px 10px;margin-bottom:14px;
}

/* math display block */
.mathline{
  background:var(--bg);border:1px solid var(--line);border-radius:14px;
  padding:16px 18px;font-size:1.5rem;text-align:center;margin:6px 0 18px;
  letter-spacing:.3px;overflow-x:auto;
}
.mathline.small{font-size:1.25rem}

/* vertical (stacked) fraction */
.frac{display:inline-flex;flex-direction:column;vertical-align:middle;text-align:center;margin:0 .2em;line-height:1.18}
.frac .fnum{padding:0 .5em 3px}
.frac .fden{padding:3px .5em 0;border-top:2px solid currentColor}

/* option buttons */
.opts{display:flex;flex-direction:column;gap:10px}
.opts.tl{flex-direction:row}
.opt{
  text-align:left;background:var(--surface-2);border:1px solid var(--line);
  color:var(--ink);border-radius:13px;padding:14px 16px;font-size:1.06rem;
  font-family:var(--body);cursor:pointer;display:flex;
  align-items:center;gap:12px;width:100%;
  transition:transform .14s var(--spring),border-color .15s,background .15s,box-shadow .15s;
}
.opt:hover:not(:disabled){border-color:#3a4658;background:#222b39;transform:translateX(5px)}
.opt .key{
  font-family:var(--display);font-weight:600;font-size:.82rem;color:var(--muted);
  border:1px solid var(--line);border-radius:8px;width:26px;height:26px;
  display:grid;place-items:center;flex:0 0 auto;
}
.opts.tl .opt{flex:1;justify-content:center;font-size:1.12rem;font-family:var(--display);font-weight:600}
.opt:disabled{cursor:default}
.opt:disabled:hover{transform:none}

/* colored Legit / Trap choices (perky) */
.opts.tl .tl-legit{background:var(--mint);color:var(--mint-dk);border-color:transparent}
.opts.tl .tl-trap{background:var(--coral);color:var(--coral-dk);border-color:transparent}
.opts.tl .tl-legit:hover:not(:disabled){transform:translateY(-3px) scale(1.03);box-shadow:0 10px 22px rgba(94,230,168,.32);background:var(--mint)}
.opts.tl .tl-trap:hover:not(:disabled){transform:translateY(-3px) scale(1.03);box-shadow:0 10px 22px rgba(255,143,163,.32);background:var(--coral)}
.opts.tl .opt:disabled{opacity:.4}
.opts.tl .opt.correct{opacity:1;animation:pickpop .42s var(--spring)}
.opts.tl .opt.wrong{opacity:1;animation:shake .4s ease}

/* MCQ / step correct-wrong states */
.opt.correct{border-color:var(--mint);background:rgba(94,230,168,.14);animation:pickpop .42s var(--spring)}
.opt.correct .key{border-color:var(--mint);color:var(--mint)}
.opt.wrong{border-color:var(--coral);background:rgba(255,143,163,.12);animation:shake .4s ease}
.opt.wrong .key{border-color:var(--coral);color:var(--coral)}
.opt .mark{margin-left:auto;font-weight:700;font-size:1.1rem}
.opt.correct .mark{color:var(--mint)}
.opt.wrong .mark{color:var(--coral)}
@keyframes pickpop{0%{transform:scale(1)}45%{transform:scale(1.04)}100%{transform:scale(1)}}
@keyframes shake{0%,100%{transform:translateX(0)}25%{transform:translateX(-6px)}75%{transform:translateX(6px)}}

/* steps (spot-the-wrong-step) */
.steps{display:flex;flex-direction:column;gap:8px}
.step{
  display:flex;gap:12px;align-items:center;text-align:left;width:100%;
  background:var(--surface-2);border:1px solid var(--line);color:var(--ink);
  border-radius:13px;padding:13px 16px;cursor:pointer;font-size:1.2rem;
  transition:transform .14s var(--spring),border-color .15s,background .15s;
}
.step:hover:not(:disabled){border-color:#3a4658;background:#222b39;transform:translateX(5px)}
.step .n{font-family:var(--display);font-weight:600;color:var(--muted);font-size:.8rem;flex:0 0 auto}
.step:disabled{cursor:default}
.step:disabled:hover{transform:none}
.step.correct{border-color:var(--mint);background:rgba(94,230,168,.14);animation:pickpop .42s var(--spring)}
.step.wrong{border-color:var(--coral);background:rgba(255,143,163,.12);animation:shake .4s ease}

/* feedback */
.feedback{margin-top:18px;border-radius:14px;padding:15px 17px;border:1px solid var(--line);background:var(--bg);animation:pop .42s var(--spring)}
@keyframes pop{from{opacity:0;transform:scale(.92) translateY(10px)}to{opacity:1;transform:none}}
.feedback.good{border-color:rgba(94,230,168,.5)}
.feedback.bad{border-color:rgba(255,143,163,.5)}
.feedback .verdict{font-family:var(--display);font-weight:600;font-size:1.05rem;display:inline-flex;align-items:center;gap:8px}
.feedback.good .verdict{color:var(--mint);animation:bounceIn .5s var(--spring)}
.feedback.bad .verdict{color:var(--coral)}
@keyframes bounceIn{0%{transform:scale(.5);opacity:0}60%{transform:scale(1.15)}100%{transform:scale(1);opacity:1}}
.feedback .why{color:#cfd7e1;margin-top:7px;font-size:.96rem}
.feedback .why b{color:var(--butter);font-weight:600}
.feedback .actions{margin-top:14px;display:flex;justify-content:flex-end}

/* results */
.result{text-align:center}
.scorering{
  width:124px;height:124px;border-radius:50%;margin:6px auto 10px;
  display:grid;place-items:center;font-family:var(--display);
  background:conic-gradient(var(--mint) var(--deg,0deg), var(--surface-2) 0);
  animation:scorePop .6s var(--spring);
}
@keyframes scorePop{0%{transform:scale(.5);opacity:0}60%{transform:scale(1.1)}100%{transform:scale(1);opacity:1}}
.scorering .inner{
  width:98px;height:98px;border-radius:50%;background:var(--surface);
  display:grid;place-items:center;flex-direction:column;
}
.scorering .pct{font-size:1.9rem;font-weight:600;line-height:1}
.scorering .lbl{font-size:.72rem;color:var(--muted);letter-spacing:1px;text-transform:uppercase}
.result h2{font-family:var(--display);font-weight:600;margin:.4rem 0 .2rem}
.diagnosis{
  text-align:left;background:var(--surface-2);border:1px solid var(--line);
  border-radius:14px;padding:16px 18px;margin:18px 0;
}
.diagnosis h3{font-family:var(--display);font-weight:600;font-size:1rem;margin:0 0 8px}
.diagnosis ul{margin:0;padding-left:18px;color:#cfd7e1}
.diagnosis li{margin:4px 0}
.cta{
  border:1px solid rgba(94,230,168,.4);border-radius:14px;padding:18px;margin-top:16px;
}
.cta h3{font-family:var(--display);font-weight:600;margin:0 0 6px}
.cta p{color:var(--muted);margin:0 0 12px;font-size:.92rem}
.result .actions{display:flex;gap:10px;justify-content:center;flex-wrap:wrap;margin-top:8px}

/* ---------- footer / disclaimer ---------- */
.footer{
  margin-top:40px;border-top:1px solid var(--line);padding-top:18px;
  color:var(--muted);font-size:.78rem;line-height:1.5;
}
.footer .nav{margin-bottom:8px}
.footer .nav a{margin-right:14px}

.back{display:inline-flex;align-items:center;gap:6px;color:var(--muted);font-size:.88rem;margin-bottom:18px;transition:color .15s,transform .15s var(--spring)}
.back:hover{color:var(--ink);text-decoration:none;transform:translateX(-3px)}

/* ---------- radical with proper vinculum (§5: never a bare √ glyph) ---------- */
.rad{display:inline-flex;align-items:flex-start;line-height:1}
.rad .root{font-size:1.05em;transform:translateY(-.04em)}
.rad .radicand{border-top:2px solid currentColor;padding:.08em .18em 0;margin-left:-.06em}
.rad3 .idx{font-size:.55em;align-self:flex-start;margin-right:-.25em;transform:translateY(.1em)}

sup{font-size:.66em}

/* ---------- confetti ---------- */
.confetti{position:fixed;width:10px;height:10px;border-radius:2px;pointer-events:none;z-index:99}

@media (max-width:480px){
  .mathline{font-size:1.28rem}
  .brand h1{font-size:1.3rem}
}

/* respect reduced-motion */
@media (prefers-reduced-motion: reduce){
  *,*::before,*::after{animation:none !important;transition:none !important}
}