*{box-sizing:border-box}
:root{--ink:#12251b;--muted:#64736a;--green:#176b45;--green2:#0e4f34;--mint:#eaf6ef;--cream:#fbfaf5;--line:#dfe9e2;--card:#fff;--shadow:0 14px 45px rgba(18,54,37,.09)}
html{scroll-behavior:smooth}
body{margin:0;font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",Arial,sans-serif;color:var(--ink);background:#f7f9f7;line-height:1.65}
a{text-decoration:none;color:inherit}
button,input,select{font:inherit}
button{appearance:none}
.top{padding:9px 7%;display:flex;justify-content:space-between;gap:20px;font-size:12px;background:linear-gradient(90deg,#0c3d29,#176b45);color:#eaf7ef;letter-spacing:.2px}
nav{padding:16px 7%;display:flex;justify-content:space-between;align-items:center;gap:25px;background:rgba(255,255,255,.94);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:10;backdrop-filter:blur(14px)}
nav a{margin-left:20px;color:#3b4b42;font-weight:650;font-size:14px}
nav a:hover{color:var(--green)}
.brand{font-size:21px!important;margin:0!important;color:var(--ink)!important;letter-spacing:-.5px}
.brand b{color:var(--green)}
.hero{padding:82px 7% 86px;display:grid;grid-template-columns:1.35fr .85fr;gap:60px;align-items:center;background:radial-gradient(circle at 85% 20%,rgba(44,150,99,.12),transparent 30%),linear-gradient(135deg,#edf8f0,#fffdf7);border-bottom:1px solid var(--line)}
.pill,.heading span{font-size:11px;font-weight:850;letter-spacing:1.8px;color:var(--green)}
.pill{display:inline-flex;padding:7px 11px;border:1px solid #cfe6d7;border-radius:999px;background:rgba(255,255,255,.72)}
.hero h1{font-size:clamp(43px,6vw,78px);line-height:1.01;letter-spacing:-3px;margin:17px 0 19px;max-width:850px}
.hero em{font-style:normal;color:var(--green)}
.hero p{font-size:18px;max-width:690px;color:#526159;margin:0 0 28px}
.btn,.search button{display:inline-flex;align-items:center;justify-content:center;background:linear-gradient(135deg,var(--green),#23845a);color:white;border:0;border-radius:12px;padding:14px 21px;font-weight:800;cursor:pointer;box-shadow:0 10px 24px rgba(23,107,69,.18);transition:.2s}
.btn:hover,.search button:hover{transform:translateY(-2px);box-shadow:0 14px 30px rgba(23,107,69,.25)}
.hero-card{position:relative;overflow:hidden;background:linear-gradient(145deg,#0d3f2a,#176b45);color:white;border-radius:28px;padding:38px;min-height:325px;box-shadow:0 25px 60px rgba(14,79,52,.22)}
.hero-card:before{content:"";position:absolute;width:220px;height:220px;border:1px solid rgba(255,255,255,.14);border-radius:50%;right:-70px;top:-70px}
.hero-card:after{content:"";position:absolute;width:140px;height:140px;border:1px solid rgba(255,255,255,.1);border-radius:50%;right:20px;bottom:-75px}
.hero-card strong{font-size:14px;letter-spacing:.8px}
.hero-card .big{font-size:clamp(80px,9vw,120px);font-weight:950;letter-spacing:-6px;line-height:1;margin:28px 0}
.hero-card p{font-size:15px;color:#dcefe4;max-width:330px}
section{padding:78px 7%;max-width:1450px;margin:auto}
.heading{margin-bottom:25px}
.heading h2{font-size:clamp(30px,4vw,42px);letter-spacing:-1.5px;margin:5px 0 0}
.grid{display:grid;gap:18px}
.cards{grid-template-columns:repeat(3,1fr)}
.classcard,.subject{border:1px solid var(--line);background:var(--card);border-radius:20px;padding:25px;text-align:left;cursor:pointer;transition:.22s;box-shadow:0 5px 18px rgba(18,54,37,.035)}
.classcard:hover,.subject:hover{transform:translateY(-5px);border-color:#acd5bd;box-shadow:var(--shadow)}
.classcard:focus-visible,.subject:focus-visible{outline:3px solid rgba(35,132,90,.25);outline-offset:2px}
.classcard span{font-size:11px;color:#7a877f;font-weight:800;letter-spacing:1px}
.classcard b{display:block;font-size:64px;line-height:1.05;color:var(--green);letter-spacing:-3px}
.classcard small{font-size:15px;color:#58675e}
.subject b{display:block;font-size:20px;margin-bottom:4px}
.subject small{color:#718078}
.subjects{grid-template-columns:repeat(4,1fr)}
.filters{display:flex;flex-wrap:wrap;gap:12px;margin-bottom:22px}
.filters select,.search input{padding:13px 15px;border:1px solid #ccd9d0;border-radius:11px;background:white;color:var(--ink);outline:none}
.filters select:focus,.search input:focus{border-color:#69ad88;box-shadow:0 0 0 4px rgba(35,132,90,.1)}
.chapter-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:14px}
.chapter{background:white;border:1px solid var(--line);border-radius:16px;padding:19px;display:block;transition:.2s;box-shadow:0 4px 15px rgba(18,54,37,.03)}
.chapter:hover{transform:translateY(-3px);border-color:#afd7be;box-shadow:var(--shadow)}
.chapter span,.qmeta{font-size:11px;color:var(--green);font-weight:800;letter-spacing:.5px}
.chapter b{display:block;font-size:18px;margin:5px 0}
.chapter small{color:#777}
.search{max-width:none;background:linear-gradient(135deg,#eaf5ee,#f4f7f2);border-top:1px solid var(--line);border-bottom:1px solid var(--line)}
.search form{display:flex;gap:10px}
.search input{flex:1;min-width:0}
.result,.question{background:white;border:1px solid var(--line);border-radius:16px;padding:20px;margin-top:14px;box-shadow:0 4px 15px rgba(18,54,37,.03)}
.question h3,.result h3{margin:8px 0}
.solution{margin-top:14px}
.solution img{max-width:100%;height:auto;border-radius:8px}
.solution table{border-collapse:collapse;width:100%;overflow:hidden}
.solution td,.solution th{border:1px solid #bbb;padding:8px}
.solution blockquote,.solution .note{padding:12px;background:#f0f7f2;border-left:4px solid var(--green);border-radius:0 8px 8px 0}
details summary{cursor:pointer;font-weight:750;color:var(--green)}
.ad-slot{margin-top:10px}
.monetization{background:#fff;border-top:1px solid var(--line);padding:34px 7%}
.monetization-inner{max-width:1450px;margin:auto;display:grid;grid-template-columns:1fr 1.6fr;gap:28px;align-items:center}
.ad-label{font-size:10px;font-weight:800;letter-spacing:1.5px;color:#87948c;text-transform:uppercase}
.ad-box{min-height:90px;border:1px dashed #cbd8cf;border-radius:14px;background:#fafcfb;display:flex;align-items:center;justify-content:center;color:#8a958e;font-size:12px}
footer{padding:40px 7%;display:grid;grid-template-columns:1.5fr 1fr 1fr;gap:30px;background:#102d20;color:#dcebe2}
footer b{color:white;letter-spacing:.3px}
footer p{color:#b7cbbf;margin:7px 0 0;font-size:14px}
.footer-note{max-width:1450px;margin:0 auto;padding:14px 7%;background:#0b2419;color:#92aa9c;font-size:11px;text-align:center}
@media(max-width:900px){.hero{grid-template-columns:1fr;gap:35px;padding-top:60px}.subjects{grid-template-columns:repeat(2,1fr)}.chapter-grid{grid-template-columns:repeat(2,1fr)}.monetization-inner{grid-template-columns:1fr}}
@media(max-width:650px){.top{font-size:11px;padding:8px 5%;flex-direction:column;gap:2px}.top span:last-child{display:none}nav{padding:13px 5%;align-items:flex-start}nav>div{display:flex;flex-wrap:wrap;justify-content:flex-end}nav a{margin-left:10px;font-size:12px}.brand{font-size:18px!important;white-space:nowrap}.hero{padding:52px 5% 60px}.hero h1{letter-spacing:-2px;font-size:43px}.hero p{font-size:16px}.hero-card{min-height:250px;padding:28px}.hero-card .big{font-size:82px}section{padding:58px 5%}.cards,.subjects,.chapter-grid{grid-template-columns:1fr}.heading h2{font-size:31px}.search form{flex-direction:column}.search button{width:100%}.monetization{padding:28px 5%}footer{grid-template-columns:1fr;padding:34px 5%}.footer-note{padding:12px 5%}}

/* Navigation interaction + persistent site navigation */
nav{
  position:sticky;
  top:0;
  z-index:1000;
  box-shadow:0 1px 0 rgba(18,54,37,.03);
}
.nav-links{
  display:flex;
  align-items:center;
  flex-wrap:wrap;
  gap:4px;
}
.nav-links .nav-link{
  position:relative;
  display:inline-flex;
  align-items:center;
  padding:7px 9px;
  margin-left:0;
  border-radius:8px;
  transition:color .22s ease, text-shadow .22s ease, background-color .22s ease;
}
.nav-links .nav-link::after{
  content:"";
  position:absolute;
  left:9px;
  right:9px;
  bottom:2px;
  height:2px;
  border-radius:99px;
  background:var(--green);
  transform:scaleX(0);
  transform-origin:center;
  opacity:0;
  transition:transform .25s ease, opacity .25s ease;
}
.nav-links .nav-link:hover,
.nav-links .nav-link:focus-visible{
  color:var(--green);
  background:rgba(35,132,90,.07);
  text-shadow:0 0 12px rgba(35,132,90,.24);
  outline:none;
}
.nav-links .nav-link:hover::after,
.nav-links .nav-link:focus-visible::after{
  transform:scaleX(1);
  opacity:1;
}
.nav-links .nav-link:active{
  background:rgba(35,132,90,.13);
}
footer{
  scroll-margin-top:90px;
}
footer > div{
  scroll-margin-top:90px;
}
.footer-links{
  display:flex;
  flex-direction:column;
  gap:4px;
}
.footer-links a{
  color:#b7cbbf;
  width:max-content;
  position:relative;
  transition:color .2s ease, text-shadow .2s ease;
}
.footer-links a:hover,
.footer-links a:focus-visible{
  color:#fff;
  text-shadow:0 0 12px rgba(255,255,255,.2);
  outline:none;
}
@media(max-width:650px){
  .nav-links{
    gap:2px;
  }
  .nav-links .nav-link{
    padding:6px 7px;
    font-size:12px;
  }
  .nav-links .nav-link::after{
    left:7px;
    right:7px;
  }
}