/* eCircuitCalc — Formula Sheet (reuses base.css tokens) */

.rprog{position:fixed;top:0;left:0;right:0;height:3px;z-index:120;pointer-events:none}
.rprog span{display:block;height:100%;width:0;background:var(--grad);transition:width .1s linear}
.article{min-height:60vh}
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);border:0}

/* ---------- Sticky formula toolbar ---------- */
.fbar{position:sticky;top:var(--nav-h);z-index:90;background:color-mix(in srgb,var(--bg) 84%,transparent);
  backdrop-filter:blur(12px);-webkit-backdrop-filter:blur(12px);border-bottom:1px solid var(--border)}
.fbar-row{display:flex;align-items:center;gap:.7rem;padding:.6rem 0}
.fsearch{flex:1;display:flex;align-items:center;gap:.55rem;background:var(--surface);border:1px solid var(--border2);
  border-radius:11px;padding:.55rem .85rem;transition:border-color .2s,box-shadow .2s}
.fsearch:focus-within{border-color:var(--accent);box-shadow:0 0 0 3px var(--glow)}
.fsearch svg{color:var(--text2);flex:none}
.fsearch input{flex:1;min-width:0;background:none;border:0;outline:0;color:var(--text);font:inherit}
.results{font-family:var(--mono);font-size:.72rem;color:var(--text2);white-space:nowrap}
.fbtn{font-size:.8rem;font-weight:600;padding:.5rem .8rem;border-radius:10px;border:1px solid var(--border2);
  background:var(--surface);color:var(--text2);white-space:nowrap;transition:.2s}
.fbtn:hover{color:var(--accent);border-color:var(--accent)}
.fbtn[aria-pressed="true"]{color:var(--accent);border-color:var(--accent)}
.fbar-chips{display:flex;gap:.4rem;overflow-x:auto;padding:.15rem 0 .75rem;scrollbar-width:thin;scrollbar-color:var(--border2) transparent}
.fbar-chips::-webkit-scrollbar{height:6px}
.fbar-chips::-webkit-scrollbar-thumb{background:var(--border2);border-radius:99px}
.fchip{flex:none;font-size:.8rem;padding:.42rem .82rem;border-radius:999px;border:1px solid var(--border);
  color:var(--text2);background:var(--surface);white-space:nowrap;transition:transform .2s var(--ease),color .2s,border-color .2s}
.fchip:hover{color:var(--accent);border-color:var(--accent);transform:translateY(-1px)}

/* ---------- Quick reference cheat sheet ---------- */
.cheat-sec{padding:2rem 4% 0;max-width:1180px;margin:0 auto}
.cheat-h{font-size:1.15rem;font-weight:800;letter-spacing:-.01em;margin-bottom:1rem}
.cheat{display:grid;grid-template-columns:repeat(auto-fill,minmax(180px,1fr));gap:.8rem}
.cheat-card{position:relative;padding:1rem;border-radius:14px;background:var(--surface);border:1px solid var(--border);
  transition:transform .25s var(--ease),border-color .25s,box-shadow .25s}
.cheat-card:hover{transform:translateY(-3px);border-color:var(--accent);box-shadow:var(--shadow)}
.cheat-card .cl{display:block;font-family:var(--mono);font-size:.66rem;letter-spacing:.08em;text-transform:uppercase;color:var(--text2)}
.cheat-card .cf{font-family:var(--mono);font-size:1.15rem;font-weight:600;color:var(--accent);margin:.35rem 0 .6rem;word-break:break-word}
.cheat-card .copy-btn{margin-top:auto}

/* ---------- Prose sections ---------- */
.prose{width:min(1180px,92%);margin:0 auto;display:grid;gap:clamp(2.4rem,5vw,3.6rem);padding:1.5rem 0 2rem}
.fsec{scroll-margin-top:132px}
.prose h2{font-size:clamp(1.35rem,3vw,1.8rem);font-weight:800;letter-spacing:-.02em;margin-bottom:.9rem}
.prose h3{font-size:1.08rem;margin:1.4rem 0 .5rem}
.prose p{color:var(--text2);margin-bottom:.9rem;line-height:1.7}
.muted{color:var(--text2);font-size:.94rem}
.prose a{color:var(--accent);text-decoration:underline;text-underline-offset:3px}

.callout{border:1px solid var(--border);border-left:3px solid var(--accent);background:var(--surface);
  border-radius:0 12px 12px 0;padding:1rem 1.2rem;margin:1.2rem 0}
.callout p{margin:0}
.callout.pitfall{border-left-color:#fbbf24}

/* expandable examples */
details.ex{margin:1.1rem 0;border:1px solid var(--border);border-radius:12px;background:var(--surface);overflow:hidden}
details.ex summary{cursor:pointer;list-style:none;padding:.85rem 1.1rem;font-weight:600;font-size:.95rem;
  display:flex;justify-content:space-between;align-items:center}
details.ex summary::-webkit-details-marker{display:none}
details.ex summary::after{content:"+";color:var(--accent);font-size:1.2rem;transition:transform .25s var(--ease)}
details.ex[open] summary::after{transform:rotate(45deg)}
details.ex p{margin:0;padding:0 1.1rem 1rem}
details.ex summary:focus-visible{outline:2px solid var(--accent);outline-offset:-2px;border-radius:12px}

.rel{margin-top:.9rem;font-size:.9rem;color:var(--text2);border-left:2px solid var(--accent);padding-left:.8rem}
.rel strong{color:var(--text)}

/* ---------- Formula tables ---------- */
.table-wrap{overflow-x:auto;border:1px solid var(--border);border-radius:14px;background:var(--surface);margin:1rem 0}
.ftable{width:100%;border-collapse:collapse;min-width:560px}
.ftable caption{caption-side:top;text-align:left;padding:.9rem 1.1rem .35rem;font-family:var(--mono);
  font-size:.68rem;letter-spacing:.1em;text-transform:uppercase;color:var(--text2)}
.ftable th,.ftable td{padding:.62rem .9rem;text-align:left;border-bottom:1px solid var(--border);font-size:.9rem;vertical-align:top}
.ftable th{font-family:var(--mono);font-size:.68rem;letter-spacing:.08em;text-transform:uppercase;color:var(--text2);
  background:var(--surface2);position:sticky;top:0}
.ftable tbody tr{transition:background .15s}
.ftable tbody tr:hover{background:var(--surface2)}
.ftable tbody tr:last-child td{border-bottom:0}
.f{font-family:var(--mono);color:var(--accent);font-weight:600}
.ftable .f{white-space:normal}
.fcopy{white-space:nowrap;text-align:right}
.copy-btn{font-family:var(--mono);font-size:.78rem;line-height:1;padding:.32rem .5rem;border-radius:8px;
  border:1px solid var(--border2);background:var(--surface2);color:var(--text2);transition:.2s;cursor:pointer}
.copy-btn:hover{color:var(--accent);border-color:var(--accent)}
.copy-btn:focus-visible{outline:2px solid var(--accent);outline-offset:2px}
.nores{margin:1rem 0;padding:1rem;border-radius:12px;border:1px dashed var(--border2);color:var(--text2);text-align:center}
.noresult{display:none;margin:1.5rem 0;padding:1.2rem;border-radius:12px;border:1px dashed var(--border2);
  color:var(--text2);text-align:center}
.noresult.show{display:block}

/* ---------- Animated SVG ---------- */
.fig-sec{padding:1rem 4% 0;max-width:1000px;margin:0 auto}
.fig{padding:1.2rem;border-radius:16px;background:var(--bg2);border:1px solid var(--border)}
.fig-svg{width:100%;height:auto;max-width:720px;margin:0 auto;display:block}
.fig figcaption{margin-top:1rem;font-size:.9rem;color:var(--text2);line-height:1.6}
.fs-wire{fill:none;stroke:var(--wbase);stroke-width:2.2;stroke-linecap:round;stroke-linejoin:round}
.fs-comp{fill:none;stroke:var(--cw);stroke-width:2.4;stroke-linecap:round;stroke-linejoin:round}
.fs-thick{stroke-width:5}
.fs-lbl{fill:var(--text);font-family:var(--mono);font-size:14px;font-weight:600}
.fs-lbl.sm{font-size:11px;fill:var(--text2);font-weight:400}
.fs-arr{fill:none;stroke:var(--accent);stroke-width:3;stroke-linecap:round;filter:drop-shadow(0 0 4px var(--glow))}
.fs-flow{fill:none;stroke:var(--accent);stroke-width:2.6;stroke-linecap:round;stroke-dasharray:7 11;
  animation:fsflow .9s linear infinite;filter:drop-shadow(0 0 4px var(--glow))}
.fs-node{fill:var(--accent);transform-box:fill-box;transform-origin:center;animation:fsnode 1.6s ease-in-out infinite}
.fs-conn{stroke:var(--border2);stroke-width:1.5;stroke-dasharray:4 6}
.fs-dot{fill:var(--accent);opacity:.8}
.fs-dot.d2{animation-delay:.5s}
.fs-dot.d3{animation-delay:1s}
.fs-dot{animation:fsdot 3s linear infinite}
.fs-guide{stroke:var(--text2);stroke-width:1;stroke-dasharray:4 5;opacity:.5}
.fs-guide.peak{stroke:var(--accent);opacity:.6}
.fs-guide.rms{stroke:var(--accent3, #8b5cf6);opacity:.6}
.fs-wav{fill:none;stroke:var(--accent);stroke-width:2.6;filter:drop-shadow(0 0 4px var(--glow))}
.fs-sine{animation:fstravel 1.3s linear infinite}
.fs-ring{fill:none;stroke:var(--accent3, #8b5cf6);stroke-width:2;transform-box:fill-box;transform-origin:center;
  animation:fsring 1.8s ease-out infinite}
.fs-panel{fill:var(--surface);stroke:var(--border);stroke-width:1.4}
.fs-chip{fill:var(--accent);font-family:var(--mono);font-size:13px;font-weight:600}
@keyframes fsflow{to{stroke-dashoffset:-18}}
@keyframes fsnode{50%{opacity:.3;transform:scale(1.5)}}
@keyframes fstravel{to{transform:translateX(-44px)}}
@keyframes fsring{0%{transform:scale(.35);opacity:.7}100%{transform:scale(1.15);opacity:0}}
@keyframes fsdot{0%{transform:translateX(0);opacity:0}12%{opacity:1}88%{opacity:1}100%{transform:translateX(650px);opacity:0}}

/* ---------- Ad slot (auto-hides when empty) ---------- */
.ad-slot{max-width:728px;margin:1.5rem auto;text-align:center;transition:max-height .5s var(--ease),opacity .4s,margin .5s;max-height:160px;overflow:hidden}
.ad-slot.ad-hidden{max-height:0;opacity:0;margin:0}
.ad-label{display:block;font-family:var(--mono);font-size:.6rem;letter-spacing:.2em;text-transform:uppercase;color:var(--text2);opacity:.6;margin-bottom:.4rem}
.ad-box{min-height:90px;border:1.5px dashed var(--border2);border-radius:12px;display:grid;place-items:center;color:var(--text2);font-size:.85rem;background:var(--surface)}

/* ---------- Symbols / refs ---------- */
.sym-sec,.refs{padding:1.5rem 4%;max-width:1180px;margin:0 auto}
.sym-sec h2,.refs h2{font-size:1.4rem;font-weight:800;letter-spacing:-.02em;margin-bottom:.4rem}
.sym-sec .muted{margin-bottom:1rem}
.refs p{color:var(--text2);line-height:1.7}

/* ---------- Reduced motion ---------- */
@media (prefers-reduced-motion:reduce){
  .rprog span{transition:none}
  .fs-flow,.fs-node,.fs-sine,.fs-ring,.fs-dot{animation:none}
  .fs-dot{opacity:0}
  .ftable tbody tr,.cheat-card,.fchip{transition:none}
}

/* ---------- Responsive ---------- */
@media (max-width:640px){
  .fsec{scroll-margin-top:168px}
  .fbar-row{flex-wrap:wrap}
  .fsearch{flex-basis:100%}
  .results{margin-left:auto}
  .fbtn{order:5}
  .ftable{min-width:520px}
  .cheat{grid-template-columns:repeat(auto-fill,minmax(150px,1fr))}
  .cheat-card .cf{font-size:1rem}
}