:root{
  --blue:#1d4ed8; --blue-dark:#1e3a8a; --navy:#0a2540; --blue-soft:#e8effc;
  --slate:#14213a; --muted:#5b6b84; --line:#d7e0ee; --bg:#f4f7fc;
  --card:#ffffff; --green:#15803d; --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(--slate);background:var(--bg);line-height:1.6;font-size:16px}
a{color:var(--blue);text-decoration:none}
a:hover{text-decoration:underline}
.wrap{max-width:1080px;margin:0 auto;padding:0 18px}
/* header */
.site-header{background:var(--card);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:50}
.site-header .wrap{display:flex;align-items:center;justify-content:space-between;min-height:64px}
.brand{font-weight:800;font-size:1.25rem;color:var(--navy);display:flex;align-items:center;gap:8px}
.brand .logo{width:30px;height:30px;border-radius:9px;background:linear-gradient(135deg,var(--blue),var(--blue-dark));
  display:inline-flex;align-items:center;justify-content:center;color:#fff;font-size:17px}
nav.main{display:flex;gap:4px;align-items:center;flex-wrap:wrap}
nav.main a{color:var(--slate);font-weight:600;padding:8px 12px;border-radius:10px;font-size:.95rem}
nav.main a:hover{background:var(--blue-soft);text-decoration:none;color:var(--blue-dark)}
#navToggle{display:none;background:none;border:1px solid var(--line);border-radius:10px;font-size:1.3rem;
  padding:6px 12px;cursor:pointer;color:var(--slate)}
/* hero */
.hero{background:linear-gradient(135deg,#0a2540 0%,#123f7b 55%,#1d4ed8 100%);color:#fff;padding:56px 0 64px}
.hero h1{margin:0 0 12px;font-size:2.1rem;line-height:1.2;letter-spacing:-.02em}
.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(255,255,255,.16);padding:6px 14px;border-radius:999px}
/* tool cards */
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:18px;margin:36px 0}
.tool-card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:24px;transition:transform .15s,box-shadow .15s}
.tool-card:hover{transform:translateY(-3px);box-shadow:0 12px 28px rgba(29,78,216,.14);text-decoration:none}
.tool-card .icon{font-size:2rem;margin-bottom:10px}
.tool-card h3{margin:0 0 8px;font-size:1.15rem;color:var(--slate)}
.tool-card p{margin:0;color:var(--muted);font-size:.94rem}
/* tool page layout */
.tool-hero{background:linear-gradient(135deg,#0a2540,#1d4ed8);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(10,37,64,.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}
.field input:focus,.field select:focus{outline:none;border-color:var(--blue);box-shadow:0 0 0 3px var(--blue-soft)}
.field-row{display:grid;grid-template-columns:1fr 1fr;gap:14px}
.field-row3{display:grid;grid-template-columns:1fr 1fr 1fr;gap:14px}
.btn{background:var(--blue);color:#fff;border:none;border-radius:12px;padding:13px 26px;
  font-size:1rem;font-weight:700;cursor:pointer;width:100%}
.btn:hover{background:var(--blue-dark)}
.btn-ghost{background:var(--blue-soft);color:var(--blue-dark)}
.result{background:#effaf2;border:1.5px solid #bbe9c6;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(--green)}
.result .detail{color:var(--muted);font-size:.92rem;margin-top:6px}
.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(--slate)}
.tabs button.active{background:var(--blue);border-color:var(--blue);color:#fff}
/* dynamic rows, stat cards, tables, textarea */
.field textarea{width:100%;padding:12px 14px;border:1.5px solid var(--line);border-radius:12px;
  font-size:1rem;font-family:inherit;min-height:170px;resize:vertical}
.field textarea:focus{outline:none;border-color:var(--blue);box-shadow:0 0 0 3px var(--blue-soft)}
.area-row{border:1.5px solid var(--line);border-radius:12px;padding:16px;margin-bottom:14px;background:#fbfcff}
.area-row .area-head{display:flex;justify-content:space-between;align-items:center;margin-bottom:10px}
.area-row .area-head strong{font-size:.98rem}
.btn-small{background:var(--blue-soft);color:var(--blue-dark);border:none;border-radius:10px;
  padding:9px 16px;font-weight:700;cursor:pointer;font-size:.9rem}
.btn-small:hover{background:#d4e2fa}
.btn-danger{background:#fef2f2;color:#b91c1c}
.btn-danger:hover{background:#fee2e2}
.stats{display:grid;grid-template-columns:repeat(auto-fill,minmax(138px,1fr));gap:12px;margin-top:4px}
.stat{background:var(--blue-soft);border-radius:12px;padding:14px 10px;text-align:center}
.stat .num{font-size:1.45rem;font-weight:800;color:var(--blue-dark);line-height:1.2}
.stat .lab{font-size:.8rem;color:var(--muted);font-weight:700;margin-top:3px}
table.bagtable{width:100%;border-collapse:collapse;margin-top:10px;font-size:.95rem}
table.bagtable th,table.bagtable td{border:1px solid var(--line);padding:8px 10px;text-align:left}
table.bagtable th{background:var(--blue-soft)}
.topwords{margin-top:16px}
.topwords li{color:#334155}
/* distance visualiser */
.viz{margin-top:16px}
.viz .bar{height:26px;border-radius:8px;background:linear-gradient(90deg,#f59e0b,#dc2626);min-width:26px;transition:width .3s}
.viz .cars{font-size:1.25rem;letter-spacing:2px;margin-top:10px;word-break:break-all}
.viz .cap{font-size:.85rem;color:var(--muted);margin-top:4px}
/* stacked stopping-distance bar */
.splitbar{display:flex;height:30px;border-radius:8px;overflow:hidden;margin-top:14px;border:1px solid var(--line)}
.splitbar .think{background:#f59e0b}
.splitbar .brake{background:#1d4ed8}
.legend{display:flex;gap:18px;font-size:.85rem;color:var(--muted);margin-top:8px;flex-wrap:wrap}
.legend .dot{display:inline-block;width:11px;height:11px;border-radius:3px;margin-right:6px;vertical-align:-1px}
/* 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:#334155}
.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(--navy);color:#c7d5ea;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:#c7d5ea;display:block;margin-bottom:8px;font-size:.93rem}
.site-footer p{font-size:.9rem;margin:0 0 10px}
.bottom-bar{border-top:1px solid #1d3f66;margin-top:28px;padding-top:18px;font-size:.85rem;color:#93a9c9}
/* breadcrumbs */
.crumbs{font-size:.85rem;color:var(--muted);margin:18px 0 0}
.crumbs a{color:var(--muted)}

/* ===== professional redesign: nav dropdown, motion, network ===== */
.site-header{box-shadow:0 2px 16px rgba(10,37,64,.08)}
.site-header .wrap{gap:16px;min-height:60px}
.brand{flex:0 0 auto;white-space:nowrap}
.brand .logo{flex:0 0 auto}
nav.main{flex-wrap:nowrap}
.nav-drop{position:relative}
.drop-btn{display:flex;align-items:center;gap:6px;background:none;border:none;font:inherit;
  font-weight:600;font-size:.95rem;color:var(--slate);padding:8px 12px;border-radius:10px;cursor:pointer}
.drop-btn:hover{background:var(--blue-soft);color:var(--blue-dark)}
.drop-btn .caret{font-size:.7rem;transition:transform .2s ease}
.drop-btn[aria-expanded="true"] .caret{transform:rotate(180deg)}
.site-header .drop-menu{position:absolute;top:calc(100% + 8px);left:50%;transform:translate(-50%,8px);
  background:#fff;border:1px solid var(--line);border-radius:14px;box-shadow:0 24px 48px rgba(10,37,64,.16);
  padding:10px;display:grid;grid-template-columns:1fr 1fr;gap:2px;min-width:440px;z-index:60;
  opacity:0;visibility:hidden;pointer-events:none;transition:opacity .2s ease,transform .2s ease}
.nav-drop:hover .drop-menu,.nav-drop:focus-within .drop-menu,.site-header .drop-menu.open{
  opacity:1;visibility:visible;pointer-events:auto;transform:translate(-50%,0)}
.site-header .drop-menu a{color:var(--slate);white-space:nowrap;padding:9px 12px;border-radius:8px}
.site-header .drop-menu a:hover{background:var(--blue-soft);color:var(--blue-dark);text-decoration:none}
/* hero + buttons */
@keyframes fadeUp{from{opacity:0;transform:translateY(14px)}to{opacity:1;transform:none}}
.hero h1{animation:fadeUp .55s ease both}
.hero p.sub{animation:fadeUp .55s .08s ease both}
.hero-cta{animation:fadeUp .55s .16s ease both}
.hero-badges{animation:fadeUp .55s .24s ease both}
.tool-hero h1{animation:fadeUp .5s ease both}
.tool-hero p{animation:fadeUp .5s .07s ease both}
.hero-cta{display:inline-flex;align-items:center;gap:8px;background:#fff;color:var(--blue-dark);
  font-weight:800;padding:14px 28px;border-radius:999px;min-height:52px;margin:0 0 26px;
  box-shadow:0 10px 24px rgba(0,0,0,.20);transition:transform .2s ease,box-shadow .2s ease}
.hero-cta:hover{transform:translateY(-2px);box-shadow:0 14px 30px rgba(0,0,0,.26);text-decoration:none}
.btn{background:linear-gradient(135deg,#2563eb,var(--blue-dark));min-height:52px;position:relative;
  overflow:hidden;box-shadow:0 8px 20px rgba(29,78,216,.25);transition:transform .2s ease,box-shadow .2s ease}
.btn:hover{background:linear-gradient(135deg,#2563eb,var(--blue-dark));transform:translateY(-1px);
  box-shadow:0 12px 26px rgba(29,78,216,.32)}
.btn:active{transform:scale(.99)}
.btn::after{content:"";position:absolute;top:0;left:-70%;width:45%;height:100%;
  background:linear-gradient(100deg,transparent,rgba(255,255,255,.35),transparent);
  transform:skewX(-20deg);transition:left .5s ease}
.btn:hover::after{left:130%}
.btn-ghost{background:var(--blue-soft);box-shadow:none}
.btn-ghost::after{display:none}
/* cards */
.tool-card{transition:transform .25s ease,box-shadow .25s ease}
.tool-card:hover{transform:translateY(-5px);box-shadow:0 18px 36px rgba(29,78,216,.16)}
.tool-card .icon{width:54px;height:54px;border-radius:14px;margin-bottom:14px;color:var(--blue);
  background:linear-gradient(135deg,var(--blue-soft),#dbe7fd);display:flex;align-items:center;justify-content:center}
.tool-card .icon svg{width:27px;height:27px}
/* scroll reveal (class added by JS only when IO exists) */
.reveal{opacity:0;transform:translateY(14px);transition:opacity .5s ease,transform .5s ease}
.reveal.in{opacity:1;transform:none}
/* network */
.network{background:#fff;border-top:1px solid var(--line);margin-top:60px;padding:36px 0 4px}
.network h3{margin:0;font-size:1.15rem;color:var(--navy)}
.net-grid{display:flex;flex-wrap:wrap;gap:10px;margin-top:16px;padding-bottom:30px}
.net-grid a{display:inline-flex;align-items:center;min-height:44px;padding:10px 18px;background:var(--card);
  border:1px solid var(--line);border-radius:999px;font-weight:700;color:var(--slate);
  transition:transform .2s ease,box-shadow .2s ease}
.net-grid a:hover{transform:translateY(-2px);box-shadow:0 10px 22px rgba(29,78,216,.14);
  text-decoration:none;color:var(--blue-dark)}
.site-footer{margin-top:0}
.footer-policy{margin-top:12px!important;color:#fff}
/* reduced motion */
@media (prefers-reduced-motion: reduce){
  *,*::before,*::after{animation-duration:.01ms!important;animation-iteration-count:1!important;
    transition-duration:.01ms!important;scroll-behavior:auto!important}
  .reveal{opacity:1!important;transform:none!important}
}

@media(max-width:860px){
  nav.main{display:none;position:absolute;top:100%;left:0;right:0;background:#fff;
    flex-direction:column;align-items:stretch;padding:10px 18px 18px;border-bottom:1px solid var(--line);
    box-shadow:0 18px 30px rgba(10,37,64,.12);max-height:calc(100vh - 60px);overflow:auto}
  nav.main.open{display:flex}
  nav.main a{padding:12px}
  .nav-drop{width:100%}
  .drop-btn{width:100%;justify-content:space-between;padding:12px}
  .site-header .drop-menu{position:static;transform:none;opacity:1;visibility:visible;pointer-events:auto;
    display:none;box-shadow:none;border:none;min-width:0;padding:2px 0 6px 12px}
  .site-header .drop-menu.open{display:grid;grid-template-columns:1fr}
  #navToggle{display:block}
  .hero h1{font-size:1.65rem}
  .field-row,.field-row3{grid-template-columns:1fr}
  .site-footer .wrap{grid-template-columns:1fr}
  .calculator{margin-top:-24px;padding:20px}
}