/* ChemBio Interactive Forms — quiz styles. Brand via --cbf-p / --cbf-a on .cbf-root */
.cbf-root{--cbf-p:#3754ED;--cbf-a:#ED008C;--cbf-ink:#20224a;--cbf-ok:#22c55e;--cbf-warn:#e5484d;
  max-width:780px;margin:0 auto;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;color:var(--cbf-ink)}
.cbf *{box-sizing:border-box}
.cbf{position:relative;background:linear-gradient(160deg,#f6f7ff, #fdf3f9 65%,#fff);
  border:1px solid #eceaf5;border-radius:22px;padding:14px;overflow:hidden}

/* top bar */
.cbf-top{display:flex;align-items:center;gap:12px;padding:6px 8px 12px;opacity:.35;transition:opacity .4s}
.cbf-top.cbf-top-on{opacity:1}
.cbf-logo{display:flex;align-items:center;gap:7px;font-weight:800;font-size:14px;letter-spacing:.3px}
.cbf-logo i{font-style:normal;width:26px;height:26px;border-radius:8px;display:grid;place-items:center;
  background:linear-gradient(135deg,var(--cbf-p),var(--cbf-a));color:#fff;font-size:12px;font-weight:900}
.cbf-count{font-size:12.5px;font-weight:800;color:#8b8fa8;white-space:nowrap}
.cbf-progress{flex:1;height:8px;background:#e9e9f4;border-radius:99px;overflow:hidden}
.cbf-bar{height:100%;width:0%;border-radius:99px;background:linear-gradient(90deg,var(--cbf-p),var(--cbf-a));
  transition:width .55s cubic-bezier(.2,.8,.2,1);position:relative}
.cbf-bar::after{content:"";position:absolute;inset:0;background:linear-gradient(90deg,transparent,rgba(255,255,255,.55),transparent);
  animation:cbf-shine 2.4s linear infinite}
@keyframes cbf-shine{from{transform:translateX(-100%)}to{transform:translateX(100%)}}
.cbf-mute{border:none;background:transparent;font-size:15px;cursor:pointer;padding:2px}
.cbf-fs{border:1px solid #e2e0ee;background:#fff;border-radius:8px;font-size:12px;font-weight:800;
  color:#5a5e7c;cursor:pointer;padding:4px 7px;line-height:1;font-family:inherit}
.cbf-fs:hover{border-color:var(--cbf-p);color:var(--cbf-p)}
.cbf-timer{display:flex;align-items:center;gap:6px;font-weight:800;font-size:13.5px;font-variant-numeric:tabular-nums;
  background:#eef1ff;border:1px solid rgba(55,84,237,.25);color:var(--cbf-ink);padding:5px 11px;border-radius:99px;white-space:nowrap}
.cbf-timer svg{width:14px;height:14px}
.cbf-timer.cbf-low{background:#fdecec;border-color:rgba(229,72,77,.4);color:var(--cbf-warn);animation:cbf-fadepulse 1.15s ease-in-out infinite}
@keyframes cbf-fadepulse{0%,100%{opacity:1}50%{opacity:.35}}

/* stage & transitions */
.cbf-stage{position:relative;min-height:220px}
.cbf-card{background:#fff;border-radius:18px;box-shadow:0 10px 28px rgba(32,34,74,.10),0 2px 8px rgba(32,34,74,.05);padding:26px 26px 22px}
.cbf-in-r{animation:cbf-inr .3s cubic-bezier(.2,.8,.2,1)}
.cbf-in-l{animation:cbf-inl .3s cubic-bezier(.2,.8,.2,1)}
.cbf-out-l{position:absolute;inset:0;animation:cbf-outl .26s ease forwards;pointer-events:none}
.cbf-out-r{position:absolute;inset:0;animation:cbf-outr .26s ease forwards;pointer-events:none}
@keyframes cbf-inr{from{opacity:0;transform:translateX(56px)}to{opacity:1;transform:none}}
@keyframes cbf-inl{from{opacity:0;transform:translateX(-56px)}to{opacity:1;transform:none}}
@keyframes cbf-outl{to{opacity:0;transform:translateX(-56px)}}
@keyframes cbf-outr{to{opacity:0;transform:translateX(56px)}}
.cbf-center{text-align:center}
.cbf-shake{animation:cbf-shake .4s}
@keyframes cbf-shake{20%,60%{transform:translateX(-7px)}40%,80%{transform:translateX(7px)}}

.cbf-h{font-size:24px;margin:0 0 8px;line-height:1.2}
.cbf-h em{font-style:normal;background:linear-gradient(120deg,var(--cbf-p),var(--cbf-a));
  -webkit-background-clip:text;background-clip:text;color:transparent}
.cbf-sub{color:#6d7089;font-size:14.5px;margin:0 0 18px;line-height:1.55}
.cbf-badge{display:inline-block;background:linear-gradient(120deg,rgba(55,84,237,.1),rgba(237,0,140,.1));
  color:var(--cbf-p);font-weight:800;font-size:11.5px;letter-spacing:1.2px;text-transform:uppercase;
  padding:6px 14px;border-radius:99px;margin-bottom:12px}
.cbf-emoji{font-size:44px;margin-bottom:8px}
.cbf-wave{display:inline-block;animation:cbf-wave 1.6s ease-in-out 2}
@keyframes cbf-wave{0%,100%{transform:rotate(0)}25%{transform:rotate(18deg)}50%{transform:rotate(-8deg)}75%{transform:rotate(12deg)}}
.cbf-chips{display:flex;justify-content:center;gap:9px;flex-wrap:wrap;margin-bottom:20px}
.cbf-chip{background:#f4f5fb;border-radius:11px;padding:7px 13px;font-size:12.5px;font-weight:700;color:#5a5e7c}

/* fields */
.cbf-field{position:relative;margin:0 auto 16px;max-width:420px;text-align:left}
.cbf-field input{width:100%;font-size:16px;padding:10px 4px 6px;color:var(--cbf-ink);
  border:none;border-bottom:2px solid #dfe0ec;background:transparent;outline:none;transition:border-color .3s}
.cbf-field label{position:absolute;left:4px;top:11px;color:#9a9cb4;font-size:15px;pointer-events:none;
  transition:all .22s cubic-bezier(.2,.8,.2,1)}
.cbf-field input:focus{border-color:var(--cbf-p)}
.cbf-field input:focus+label,.cbf-field input:not(:placeholder-shown)+label{
  top:-11px;font-size:11px;font-weight:800;color:var(--cbf-p);letter-spacing:.4px;text-transform:uppercase}
.cbf-field.cbf-bad input{border-color:var(--cbf-warn)}
.cbf-err{display:none;color:var(--cbf-warn);font-size:12px;font-weight:700;padding-top:5px}
.cbf-field.cbf-bad .cbf-err{display:block}
.cbf-hintline{color:#9a9cb4;font-size:12.5px;font-weight:600;margin:-6px 0 16px}

/* buttons */
.cbf-btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;
  font-size:15px;font-weight:800;border:none;border-radius:13px;padding:13px 28px;cursor:pointer;color:#fff;
  background:linear-gradient(135deg,var(--cbf-p),var(--cbf-a));
  box-shadow:0 8px 20px rgba(55,84,237,.30);
  transition:transform .16s cubic-bezier(.2,.8,.2,1),box-shadow .16s;-webkit-tap-highlight-color:transparent}
.cbf-btn:hover{transform:translateY(-2px);box-shadow:0 12px 26px rgba(237,0,140,.35)}
.cbf-btn:active{transform:scale(.97)}
.cbf-btn:disabled{opacity:.45;cursor:not-allowed;transform:none!important;box-shadow:none}
.cbf-btn.cbf-ghost{background:transparent;color:#8b8fa8;box-shadow:none;font-weight:700}
.cbf-btn.cbf-ghost:hover{color:var(--cbf-ink)}
.cbf-spin{width:14px;height:14px;border:2.5px solid rgba(255,255,255,.4);border-top-color:#fff;border-radius:50%;
  display:inline-block;animation:cbf-rot .7s linear infinite}
.cbf-spin[hidden],.cbf [hidden]{display:none!important}
@keyframes cbf-rot{to{transform:rotate(360deg)}}

/* question */
.cbf-qhead{display:flex;align-items:center;justify-content:space-between;margin-bottom:12px}
.cbf-qnum{font-size:13px;font-weight:900;letter-spacing:1.4px;text-transform:uppercase;
  background:linear-gradient(120deg,var(--cbf-p),var(--cbf-a));-webkit-background-clip:text;background-clip:text;color:transparent}
.cbf-qnum i{font-style:normal;color:#b9bccd;-webkit-text-fill-color:#b9bccd}
.cbf-flagwrap{display:flex;align-items:center;gap:8px;cursor:pointer;-webkit-tap-highlight-color:transparent;
  border-radius:99px;padding:4px 6px 4px 12px;transition:background .18s}
.cbf-flagwrap:hover{background:#fff7e0}
.cbf-flaghint{font-size:12px;font-weight:700;color:#b3a06a;white-space:nowrap}
@media (max-width:520px){.cbf-flaghint{display:none}}
.cbf-flag{font-size:19px;filter:grayscale(1);opacity:.45;transition:all .2s;line-height:1}
.cbf-flagwrap:hover .cbf-flag{opacity:.8;transform:scale(1.15)}
.cbf-flag.cbf-flag-on{filter:none;opacity:1;transform:scale(1.12);animation:cbf-flagpop .3s cubic-bezier(.34,1.56,.64,1)}
@keyframes cbf-flagpop{50%{transform:scale(1.45) rotate(12deg)}}

/* image enlarge — the button lives BELOW the image so it never covers
   the printed answer options inside past-paper images */
.cbf-qimg img{cursor:zoom-in}
.cbf-qimg{margin-bottom:6px}
.cbf-imgbar{display:flex;justify-content:flex-end;margin:0 0 14px}
.cbf-zoom{border:1px solid rgba(55,84,237,.3);cursor:pointer;
  background:#eef1ff;color:var(--cbf-p);font-size:12px;font-weight:800;
  padding:6px 14px;border-radius:99px;font-family:inherit;
  transition:all .15s;-webkit-tap-highlight-color:transparent}
.cbf-zoom:hover{background:var(--cbf-p);color:#fff}
.cbf-imgfail{border:2px dashed #e3e1ef;border-radius:13px;padding:26px;text-align:center;
  color:#8b8fa8;font-weight:700;font-size:14px;margin-bottom:6px}
.cbf-imgfail .cbf-btn{margin-top:10px;padding:10px 22px}
.cbf-lightbox{position:fixed;inset:0;z-index:99999;background:rgba(12,12,28,.93);
  overflow:auto;display:flex;align-items:center;justify-content:center;padding:26px;
  animation:cbf-lb-in .2s ease}
@keyframes cbf-lb-in{from{opacity:0}to{opacity:1}}
.cbf-lightbox img{max-width:96vw;max-height:88vh;border-radius:10px;background:#fff;cursor:zoom-in;display:block}
.cbf-lightbox.cbf-lb-zoomed{display:block}
.cbf-lightbox.cbf-lb-zoomed img{max-width:none;width:175vw;max-height:none;margin:60px auto;cursor:zoom-out}
@media (min-width:900px){.cbf-lightbox.cbf-lb-zoomed img{width:130vw}}
.cbf-lb-close{position:fixed;top:14px;right:16px;z-index:2;border:none;cursor:pointer;
  width:40px;height:40px;border-radius:50%;background:rgba(255,255,255,.15);color:#fff;
  font-size:17px;font-weight:800;font-family:inherit}
.cbf-lb-close:hover{background:rgba(255,255,255,.3)}
.cbf-lb-hint{position:fixed;bottom:12px;left:0;right:0;text-align:center;color:rgba(255,255,255,.55);
  font-size:12.5px;font-weight:600;pointer-events:none}
.cbf-qtext{font-size:16.5px;font-weight:600;line-height:1.5;margin:0 0 14px}
.cbf-qimg{border:1px solid #ececf4;border-radius:13px;overflow:hidden;margin-bottom:18px;background:#fff}
.cbf-qimg img{display:block;width:100%;height:auto}

.cbf-opts{display:grid;grid-template-columns:1fr 1fr;gap:11px}
@media (max-width:600px){.cbf-opts{grid-template-columns:1fr}.cbf-card{padding:20px 16px}.cbf-h{font-size:20px}}
.cbf-opt{position:relative;overflow:hidden;display:flex;align-items:center;gap:12px;text-align:left;
  border:2px solid #e8e6f2;border-radius:13px;background:#fff;padding:13px 15px;cursor:pointer;
  font-size:15.5px;font-weight:700;color:var(--cbf-ink);font-family:inherit;
  transition:all .16s cubic-bezier(.2,.8,.2,1);-webkit-tap-highlight-color:transparent}
.cbf-opt:hover{border-color:rgba(55,84,237,.5);transform:translateY(-2px);box-shadow:0 6px 16px rgba(55,84,237,.14)}
.cbf-opt:active{transform:scale(.98)}
.cbf-letter{width:33px;height:33px;flex:none;border-radius:10px;display:grid;place-items:center;
  background:#f1f2fa;color:var(--cbf-p);font-weight:900;font-size:14.5px;transition:all .16s}
.cbf-opt.cbf-sel{border-color:var(--cbf-a);background:linear-gradient(120deg,rgba(55,84,237,.06),rgba(237,0,140,.07));
  box-shadow:0 6px 18px rgba(237,0,140,.18);animation:cbf-selpop .24s cubic-bezier(.34,1.56,.64,1)}
@keyframes cbf-selpop{50%{transform:scale(1.025)}}
.cbf-opt.cbf-sel .cbf-letter{background:linear-gradient(135deg,var(--cbf-p),var(--cbf-a));color:#fff;transform:scale(1.1)}
.cbf-tick{margin-left:auto;flex:none;color:var(--cbf-ok);opacity:0;transform:scale(.4);
  transition:all .2s cubic-bezier(.34,1.56,.64,1)}
.cbf-opt.cbf-sel .cbf-tick{opacity:1;transform:scale(1)}
.cbf-ripple{position:absolute;width:12px;height:12px;border-radius:50%;pointer-events:none;
  background:rgba(55,84,237,.25);transform:translate(-50%,-50%) scale(0);opacity:0}
.cbf-ripple-go{animation:cbf-ripple .5s ease-out}
@keyframes cbf-ripple{from{transform:translate(-50%,-50%) scale(0);opacity:1}to{transform:translate(-50%,-50%) scale(28);opacity:0}}

.cbf-nav{display:flex;justify-content:space-between;align-items:center;margin-top:20px}

/* review tiles */
.cbf-tiles{display:grid;grid-template-columns:repeat(5,1fr);gap:10px;margin:14px 0 6px}
@media (max-width:480px){.cbf-tiles{grid-template-columns:repeat(4,1fr)}}
.cbf-tile{position:relative;aspect-ratio:1;border-radius:13px;display:grid;place-items:center;
  font-weight:900;font-size:15px;cursor:pointer;border:2px solid #e8e6f2;color:#a3a6bd;background:#fff;
  font-family:inherit;transition:all .16s}
.cbf-tile:hover{transform:translateY(-2px)}
.cbf-tile-done{background:var(--cbf-ok);border-color:var(--cbf-ok);color:#fff;box-shadow:0 5px 14px rgba(34,197,94,.3)}
.cbf-tile-miss{border-color:#f4b6b8;color:var(--cbf-warn);background:#fff7f7}
.cbf-tile-flag{position:absolute;top:-13px;right:-10px;font-size:22px;filter:drop-shadow(0 2px 4px rgba(0,0,0,.25));animation:cbf-starpulse 1.6s ease-in-out infinite}
@keyframes cbf-starpulse{0%,100%{transform:scale(1) rotate(0)}50%{transform:scale(1.25) rotate(10deg)}}
.cbf-tile-flagged{border-width:3px;border-color:#f5b301;box-shadow:0 6px 18px rgba(245,179,1,.35)}
.cbf-missnote{color:var(--cbf-warn);font-weight:800;font-size:13px;margin:6px 0 0}

/* toast */
.cbf-toast{position:absolute;left:50%;bottom:18px;transform:translateX(-50%) translateY(20px);z-index:5;
  background:var(--cbf-ink);color:#fff;font-size:13.5px;font-weight:700;padding:10px 18px;border-radius:99px;
  opacity:0;pointer-events:none;white-space:nowrap;box-shadow:0 8px 24px rgba(32,34,74,.35)}
.cbf-toast-show{animation:cbf-toast 1.9s cubic-bezier(.2,.8,.2,1)}
@keyframes cbf-toast{0%{opacity:0;transform:translateX(-50%) translateY(20px)}12%,80%{opacity:1;transform:translateX(-50%) translateY(0)}100%{opacity:0;transform:translateX(-50%) translateY(-8px)}}

/* success check */
.cbf-check{width:92px;height:92px;margin:6px auto 18px;border-radius:50%;
  background:radial-gradient(circle at 30% 25%,#4ade80,var(--cbf-ok));display:grid;place-items:center;
  box-shadow:0 14px 34px rgba(34,197,94,.4);animation:cbf-inr .5s cubic-bezier(.34,1.56,.64,1)}
.cbf-check svg{width:46px;height:46px}
.cbf-check path{stroke:#fff;stroke-width:7;fill:none;stroke-linecap:round;stroke-linejoin:round;
  stroke-dasharray:80;stroke-dashoffset:80;animation:cbf-draw .7s .25s cubic-bezier(.2,.8,.2,1) forwards}
@keyframes cbf-draw{to{stroke-dashoffset:0}}

/* results */
.cbf-marking{padding:20px 0 10px}
.cbf-spin-big{width:38px;height:38px;border-width:4px;border-color:rgba(55,84,237,.2);border-top-color:var(--cbf-p)}
.cbf-gauge{position:relative;width:170px;height:170px;margin:14px auto 8px}
.cbf-gauge svg{width:100%;height:100%;transform:rotate(-90deg)}
.cbf-gauge-bg{fill:none;stroke:#eef0f8;stroke-width:11}
.cbf-gauge-fg{fill:none;stroke-width:11;stroke-linecap:round;transition:stroke-dashoffset .2s linear}
.cbf-gauge-num{position:absolute;inset:0;display:grid;place-items:center;font-weight:900}
.cbf-gauge-num b{font-size:44px;line-height:1;background:linear-gradient(120deg,var(--cbf-p),var(--cbf-a));
  -webkit-background-clip:text;background-clip:text;color:transparent}
.cbf-gauge-num span{font-size:15px;color:#9a9cb4;margin-top:2px}
.cbf-scoreline{font-size:14px;font-weight:800;color:#5a5e7c;margin:2px 0 10px}
.cbf-comment{font-size:16.5px;font-weight:800;line-height:1.45;max-width:430px;margin:0 auto 8px}
.cbf-wrongwrap{margin-top:18px;border-top:1px dashed #e4e2ef;padding-top:16px}
.cbf-wrongtitle{font-size:16px;margin:0 0 4px}
.cbf-tiles-wrong{grid-template-columns:repeat(auto-fill,minmax(52px,1fr))}
.cbf-reviewbadge{background:#fff3cd;color:#8a6d00;font-size:11px;font-weight:900;letter-spacing:1px;
  text-transform:uppercase;padding:4px 10px;border-radius:99px}
.cbf-youranswer{font-size:14.5px;font-weight:700;color:#5a5e7c;background:#f6f7fd;border-radius:11px;padding:11px 14px;margin:4px 0 0}

/* characters */
.cbf-charimg{width:130px;height:auto;margin:6px auto 4px;display:block;border-radius:18px}
.cbf-medalimg{width:150px;height:auto;margin:2px auto -6px;display:block;
  animation:cbf-medal-in .7s cubic-bezier(.34,1.56,.64,1)}
@keyframes cbf-medal-in{from{opacity:0;transform:scale(.4) rotate(-8deg)}to{opacity:1;transform:none}}
.cbf-streak{display:flex;align-items:center;justify-content:center;gap:10px;
  background:#fff7ed;border:1.5px solid #fdba74;border-radius:14px;
  padding:8px 16px;margin:4px auto 10px;max-width:340px;font-size:14.5px;font-weight:700;color:#9a3412}
.cbf-streak img{width:52px;height:auto;border-radius:10px}
.cbf-cheerpop{position:absolute;right:14px;top:58px;z-index:6;pointer-events:none;
  background:#fff;border-radius:16px;box-shadow:0 10px 28px rgba(32,34,74,.22);padding:6px;
  animation:cbf-cheer-in .45s cubic-bezier(.34,1.56,.64,1)}
.cbf-cheerpop img{width:92px;height:auto;display:block;border-radius:12px}
@keyframes cbf-cheer-in{from{opacity:0;transform:translateY(-26px) scale(.5)}to{opacity:1;transform:none}}
.cbf-cheerpop-out{opacity:0;transform:translateY(-14px) scale(.8);transition:all .45s ease}

/* practice mode + revealed answers */
.cbf-chip-practice{background:#fff3cd;color:#8a6d00}
.cbf-practicenote{font-size:13.5px;font-weight:800;color:#8a6d00;background:#fff8e1;
  border:1px solid #f5d87a;border-radius:11px;padding:9px 14px;margin:10px auto 0;max-width:380px}
.cbf-correctanswer{font-size:14.5px;font-weight:800;color:#116b3d;background:#e9f9f0;
  border:1px solid #9adbb8;border-radius:11px;padding:11px 14px;margin:10px 0 0}

/* RTL (Arabic interface) */
[dir="rtl"] .cbf-field input{text-align:right}
[dir="rtl"] .cbf-field label{left:auto;right:4px}
[dir="rtl"] .cbf-field input:focus+label,[dir="rtl"] .cbf-field input:not(:placeholder-shown)+label{left:auto;right:4px}
[dir="rtl"] .cbf-tile-flag{right:auto;left:-10px}
[dir="rtl"] .cbf-cheerpop{right:auto;left:14px}

/* confetti */
.cbf-confetti{position:fixed;top:-14px;width:9px;height:15px;z-index:9999;pointer-events:none;animation:cbf-fall linear forwards}
@keyframes cbf-fall{to{transform:translateY(105vh) rotate(720deg);opacity:.2}}

.cbf-sink{display:none}

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