:root{
  --amber:#f59e0b; --amber-dark:#b45309; --amber-soft:#fef3c7;
  --ink:#17171c; --charcoal:#232329; --muted:#6b7280; --line:#e5e2d9; --bg:#faf9f6;
  --card:#ffffff; --green:#047857; --radius:16px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Inter,Arial,sans-serif;
  color:var(--ink);background:var(--bg);line-height:1.6;font-size:16px}
a{color:var(--amber-dark);text-decoration:none}
a:hover{text-decoration:underline}
.wrap{max-width:1080px;margin:0 auto;padding:0 18px}
/* header */
.site-header{background:var(--ink);border-bottom:3px solid var(--amber);position:sticky;top:0;z-index:60;
  box-shadow:0 4px 18px rgba(0,0,0,.28)}
.site-header .wrap{display:flex;align-items:center;justify-content:space-between;gap:16px;min-height:64px}
.brand{font-weight:800;font-size:1.25rem;color:#fff;display:flex;align-items:center;gap:9px;
  flex:0 0 auto;white-space:nowrap}
.brand .logo{width:34px;height:34px;flex:0 0 auto;border-radius:10px;background:linear-gradient(135deg,var(--amber),#fbbf24);
  display:inline-flex;align-items:center;justify-content:center;color:#17171c;font-size:19px}
nav.main{display:flex;gap:2px;align-items:center}
nav.main>a{color:#e7e5e4;font-weight:600;padding:10px 12px;border-radius:10px;font-size:.95rem;white-space:nowrap}
nav.main>a:hover{background:#2e2e36;text-decoration:none;color:var(--amber)}
.nav-drop{position:relative}
.nav-drop-btn{background:none;border:none;color:#e7e5e4;font:inherit;font-weight:600;font-size:.95rem;
  padding:10px 12px;border-radius:10px;cursor:pointer;display:flex;align-items:center;gap:6px;min-height:44px}
.nav-drop-btn:hover,.nav-drop.open .nav-drop-btn{background:#2e2e36;color:var(--amber)}
.nav-drop-btn .caret{font-size:.7rem;transition:transform .25s ease}
.nav-drop.open .nav-drop-btn .caret{transform:rotate(180deg)}
.nav-drop-panel{display:none;position:absolute;top:calc(100% + 10px);right:0;width:560px;max-width:88vw;
  grid-template-columns:1fr 1fr;gap:2px;background:#1d1d23;border:1px solid #3a3a44;border-radius:14px;
  padding:10px;box-shadow:0 24px 50px rgba(0,0,0,.45)}
.nav-drop.open .nav-drop-panel{display:grid}
.nav-drop-panel a{color:#e7e5e4;font-weight:600;font-size:.92rem;padding:10px 12px;border-radius:9px;line-height:1.35}
.nav-drop-panel a:hover{background:#2e2e36;color:var(--amber);text-decoration:none}
#navToggle{display:none;background:none;border:1px solid #3f3f46;border-radius:10px;font-size:1.3rem;
  padding:6px 12px;cursor:pointer;color:#fff;min-width:44px;min-height:44px;flex:0 0 auto}
/* hero */
.hero{background:linear-gradient(135deg,#17171c 0%,#2b2b33 55%,#4a3606 125%);color:#fff;padding:56px 0 64px}
.hero h1{margin:0 0 12px;font-size:2.1rem;line-height:1.2;letter-spacing:-.02em}
.hero h1 .hl{color:var(--amber)}
.hero p.sub{opacity:.92;font-size:1.08rem;max-width:640px;margin:0 0 24px}
.hero-badges{display:flex;gap:10px;flex-wrap:wrap;font-size:.85rem}
.hero-badges span{background:rgba(245,158,11,.18);border:1px solid rgba(245,158,11,.35);padding:6px 14px;border-radius:999px}
.hero-cta{margin:26px 0 22px}
.btn-hero{display:inline-flex;align-items:center;gap:10px;background:linear-gradient(135deg,var(--amber),#fbbf24);
  color:#17171c;font-weight:800;font-size:1.05rem;padding:15px 34px;border-radius:14px;min-height:52px;
  box-shadow:0 10px 26px rgba(245,158,11,.35);transition:transform .25s ease,box-shadow .25s ease;
  position:relative;overflow:hidden}
.btn-hero:hover{transform:translateY(-2px) scale(1.02);box-shadow:0 16px 34px rgba(245,158,11,.45);
  text-decoration:none;color:#17171c}
.btn-hero::after{content:"";position:absolute;top:0;left:-80%;width:45%;height:100%;
  background:linear-gradient(100deg,transparent,rgba(255,255,255,.45),transparent);
  transform:skewX(-20deg);transition:left .5s ease}
.btn-hero:hover::after{left:135%}
/* tool cards */
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:18px;margin:36px 0;scroll-margin-top:84px}
.tool-card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:24px;transition:transform .25s ease,box-shadow .25s ease,border-color .25s ease;display:block}
.tool-card:hover{transform:translateY(-5px);box-shadow:0 16px 34px rgba(245,158,11,.22);
  border-color:#fcd34d;text-decoration:none}
.tool-card .icon{width:52px;height:52px;border-radius:14px;margin-bottom:14px;
  background:linear-gradient(135deg,var(--amber),#fbbf24);color:#17171c;
  display:flex;align-items:center;justify-content:center;
  box-shadow:0 6px 14px rgba(245,158,11,.30)}
.tool-card .icon svg{width:28px;height:28px;display:block}
.tool-card h3{margin:0 0 8px;font-size:1.15rem;color:var(--ink)}
.tool-card p{margin:0;color:var(--muted);font-size:.94rem}
/* tool page layout */
.tool-hero{background:linear-gradient(135deg,#17171c,#2b2b33 60%,#4a3606 130%);color:#fff;padding:40px 0}
.tool-hero h1{margin:0 0 8px;font-size:1.8rem;letter-spacing:-.02em}
.tool-hero p{margin:0;opacity:.9;max-width:680px}
.calculator{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:26px;margin:-34px 0 30px;box-shadow:0 10px 30px rgba(23,23,28,.10);position:relative}
.field{margin-bottom:16px}
.field label{display:block;font-weight:700;margin-bottom:6px;font-size:.95rem}
.field input,.field select{width:100%;padding:12px 14px;border:1.5px solid var(--line);border-radius:12px;
  font-size:1rem;font-family:inherit;background:#fff}
.field input:focus,.field select:focus{outline:none;border-color:var(--amber);box-shadow:0 0 0 3px var(--amber-soft)}
.field-row{display:grid;grid-template-columns:1fr 1fr;gap:14px}
.btn{background:linear-gradient(135deg,var(--amber),#fbbf24);color:#17171c;border:none;border-radius:12px;
  padding:14px 26px;font-size:1rem;font-weight:800;cursor:pointer;width:100%;min-height:50px;
  box-shadow:0 8px 20px rgba(245,158,11,.28);transition:transform .25s ease,box-shadow .25s ease;
  position:relative;overflow:hidden}
.btn:hover{transform:translateY(-1px) scale(1.01);box-shadow:0 12px 26px rgba(245,158,11,.38);color:#17171c}
.btn::after{content:"";position:absolute;top:0;left:-80%;width:45%;height:100%;
  background:linear-gradient(100deg,transparent,rgba(255,255,255,.45),transparent);
  transform:skewX(-20deg);transition:left .5s ease}
.btn:hover::after{left:135%}
.btn-ghost{background:var(--amber-soft);color:var(--amber-dark)}
.btn-ghost:hover{background:#fde68a;color:var(--amber-dark)}
.result{background:#fffbeb;border:1.5px solid #fcd34d;border-radius:12px;padding:18px;margin-top:18px;display:none}
.result.show{display:block}
.result .big{font-size:1.9rem;font-weight:800;color:var(--amber-dark)}
.result .detail{color:#57534e;font-size:.92rem;margin-top:6px}
.result .warn{color:#b91c1c;font-weight:700}
.tabs{display:flex;gap:8px;margin-bottom:18px;flex-wrap:wrap}
.tabs button{border:1.5px solid var(--line);background:#fff;border-radius:999px;padding:9px 18px;
  font-weight:700;cursor:pointer;font-size:.92rem;color:var(--ink)}
.tabs button.active{background:var(--ink);border-color:var(--ink);color:var(--amber)}
/* misc components */
.stats{display:grid;grid-template-columns:repeat(auto-fill,minmax(138px,1fr));gap:12px;margin-top:4px}
.stat{background:var(--amber-soft);border-radius:12px;padding:14px 10px;text-align:center}
.stat .num{font-size:1.45rem;font-weight:800;color:var(--amber-dark);line-height:1.2}
.stat .lab{font-size:.8rem;color:var(--muted);font-weight:700;margin-top:3px}
table.datatable{width:100%;border-collapse:collapse;margin-top:10px;font-size:.95rem}
table.datatable th,table.datatable td{border:1px solid var(--line);padding:8px 10px;text-align:left}
table.datatable th{background:var(--amber-soft)}
.disclaimer{background:#fffbeb;border:1px solid #fcd34d;border-left:5px solid var(--amber);
  border-radius:10px;padding:14px 16px;margin-top:18px;font-size:.92rem;color:#57534e}
.resistor-viz{display:flex;align-items:center;gap:0;margin:6px 0 18px}
.resistor-viz .lead{flex:1;height:4px;background:#a8a29e;border-radius:2px}
.resistor-viz .rbody{background:#e7c98a;border:2px solid #c9a44f;border-radius:14px;padding:12px 18px;
  display:flex;gap:14px;align-items:center}
.resistor-viz .band{width:14px;height:44px;border-radius:3px;background:#000}
/* content sections */
.section{margin:40px 0}
.section h2{font-size:1.45rem;margin:0 0 14px;letter-spacing:-.01em}
.prose{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:26px}
.prose h3{margin:22px 0 8px;font-size:1.1rem}
.prose h3:first-child{margin-top:0}
.prose p,.prose li{color:#292524}
.prose code{background:var(--amber-soft);padding:1px 6px;border-radius:6px;font-size:.92em}
.faq details{border:1px solid var(--line);border-radius:12px;padding:14px 16px;margin-bottom:10px;background:#fff}
.faq summary{font-weight:700;cursor:pointer}
/* footer */
.site-footer{background:var(--ink);color:#d6d3d1;padding:40px 0;margin-top:60px}
.site-footer .wrap{display:grid;grid-template-columns:1.4fr 1fr 1fr;gap:28px}
.site-footer h4{color:#fff;margin:0 0 12px;font-size:1rem}
.site-footer a{color:#d6d3d1;display:block;margin-bottom:8px;font-size:.93rem}
.site-footer a:hover{color:var(--amber)}
.site-footer p{font-size:.9rem;margin:0 0 10px}
.bottom-bar{border-top:1px solid #2e2e36;margin-top:28px;padding-top:18px;font-size:.85rem;color:#a8a29e}
/* breadcrumbs */
.crumbs{font-size:.85rem;color:var(--muted);margin:18px 0 0}
.crumbs a{color:var(--muted)}
@media(max-width:760px){
  #navToggle{display:block}
  nav.main{display:none;position:absolute;top:100%;left:0;right:0;background:var(--ink);
    flex-direction:column;align-items:stretch;padding:10px 18px 18px;border-bottom:3px solid var(--amber);
    box-shadow:0 24px 40px rgba(0,0,0,.35);max-height:calc(100vh - 67px);overflow:auto}
  nav.main.open{display:flex}
  nav.main>a{padding:13px 12px}
  .nav-drop-btn{width:100%;justify-content:space-between;padding:13px 12px}
  nav.main .nav-drop-panel{display:grid;position:static;width:auto;max-width:none;grid-template-columns:1fr;
    background:transparent;border:none;box-shadow:none;padding:0 0 6px}
  .nav-drop-panel a{padding:11px 12px 11px 24px}
  .hero h1{font-size:1.65rem}
  .field-row{grid-template-columns:1fr}
  .site-footer .wrap{grid-template-columns:1fr}
  .calculator{margin-top:-24px;padding:20px}
}
/* network cross-links */
.network{background:#fff;border-top:1px solid var(--line);padding:38px 0;margin-top:60px}
.network + .site-footer{margin-top:0}
.network h2{font-size:1.2rem;margin:0 0 8px;text-align:center;letter-spacing:-.01em}
.network p{margin:0 0 18px;text-align:center;color:var(--muted);font-size:.94rem}
.network-row{display:flex;flex-wrap:wrap;gap:10px;justify-content:center}
.network-row a{border:1.5px solid var(--line);background:var(--bg);color:var(--ink);font-weight:700;
  padding:10px 18px;border-radius:999px;min-height:44px;display:inline-flex;align-items:center;
  transition:transform .25s ease,box-shadow .25s ease,border-color .25s ease,color .25s ease}
.network-row a:hover{transform:translateY(-2px);border-color:var(--amber);color:var(--amber-dark);
  box-shadow:0 8px 20px rgba(245,158,11,.18);text-decoration:none}
/* entrance motion */
@keyframes fadeUp{from{opacity:0;transform:translateY(16px)}to{opacity:1;transform:none}}
.rv{animation:fadeUp .7s cubic-bezier(.22,.61,.36,1) both}
@media (prefers-reduced-motion: reduce){
  *,*::before,*::after{animation-duration:.01ms !important;animation-iteration-count:1 !important;
    transition-duration:.01ms !important}
  html{scroll-behavior:auto}
}