*{
margin:0;
padding:0;
box-sizing:border-box;
font-family:'Poppins',sans-serif;
}

body{
background:linear-gradient(135deg,#0f172a,#1e293b);
color:white;
min-height:100vh;
}

/* HERO SECTION */
.hero{
text-align:center;
padding:80px 20px 40px;
}

.hero h1{
font-size:42px;
font-weight:700;
margin-bottom:15px;
background:linear-gradient(to right,#38bdf8,#2563eb);
-webkit-background-clip:text;
-webkit-text-fill-color:transparent;
}

.hero p{
color:#cbd5e1;
font-size:18px;
max-width:700px;
margin:auto;
line-height:1.6;
}

/* MAIN CONTAINER */
.container{
max-width:1000px;
margin:auto;
padding:30px 20px 80px;
}
/* ===============================
UNIQUE PREMIUM SELECTOR CARD
Different from feature cards
=============================== */

.selector-card{
position: relative;
background: linear-gradient(145deg, rgba(37,99,235,0.12), rgba(56,189,248,0.06));
border: 1px solid rgba(56,189,248,0.18);
border-radius: 28px;
padding: 45px 35px;
margin-bottom: 50px;
box-shadow:
0 20px 45px rgba(0,0,0,0.20),
inset 0 1px 0 rgba(255,255,255,0.06);
backdrop-filter: blur(20px);
overflow: hidden;
}

/* Decorative Glow */
.selector-card::before{
content: "";
position: absolute;
top: -80px;
right: -80px;
width: 180px;
height: 180px;
background: rgba(56,189,248,0.12);
border-radius: 50%;
filter: blur(50px);
}

.selector-card::after{
content: "";
position: absolute;
bottom: -70px;
left: -70px;
width: 160px;
height: 160px;
background: rgba(37,99,235,0.12);
border-radius: 50%;
filter: blur(50px);
}

/* Grid Layout */
.form-grid{
position: relative;
z-index: 2;
display: grid;
grid-template-columns: 1fr 1fr;
gap: 22px;
margin-bottom: 28px;
}

/* Select Fields */
.form-grid select{
width: 100%;
padding: 18px 20px;
border: 1px solid rgba(255,255,255,0.08);
border-radius: 18px;
background: rgba(255,255,255,0.95);
font-size: 16px;
font-weight: 500;
color: #111827;
outline: none;
transition: all 0.3s ease;
box-shadow: 0 8px 20px rgba(0,0,0,0.05);
}

.form-grid select:focus{
border-color: #38bdf8;
transform: translateY(-2px);
box-shadow: 0 10px 25px rgba(56,189,248,0.15);
}

/* Search Button */
.search-btn{
position: relative;
z-index: 2;
width: 100%;
padding: 18px;
border: none;
border-radius: 18px;
background: linear-gradient(135deg,#2563eb,#38bdf8);
color: white;
font-size: 17px;
font-weight: 700;
letter-spacing: 0.5px;
cursor: pointer;
transition: all 0.3s ease;
box-shadow: 0 12px 25px rgba(37,99,235,0.28);
}

.search-btn:hover{
transform: translateY(-3px) scale(1.01);
box-shadow: 0 18px 35px rgba(37,99,235,0.35);
}

.search-btn:active{
transform: scale(0.98);
}

/* Mobile Responsive */
@media(max-width:768px){
.form-grid{
grid-template-columns: 1fr;
gap: 16px;
}

.selector-card{
padding: 28px 20px;
border-radius: 22px;
}

.search-btn{
font-size: 16px;
padding: 16px;
}
}

/* FEATURE INFO */
.info-section{
margin-top:40px;
display:grid;
grid-template-columns:repeat(3,1fr);
gap:20px;
}

.info-card{
background:rgba(255,255,255,0.04);
padding:25px;
border-radius:20px;
text-align:center;
transition:0.3s;
}

.info-card:hover{
transform:translateY(-6px);
background:rgba(255,255,255,0.06);
}

.info-card h3{
margin:15px 0 10px;
font-size:20px;
}

.info-card p{
font-size:14px;
color:#cbd5e1;
line-height:1.6;
}

.icon{
font-size:34px;
}

/* MOBILE */
@media(max-width:768px){
.hero h1{
font-size:30px;
}

.form-grid{
grid-template-columns:1fr;
}

.info-section{
grid-template-columns:1fr;
}

.selector-card{
padding:25px;
}
}

/* =========================
PREMIUM NAVBAR CSS
========================= */

*{
margin:0;
padding:0;
box-sizing:border-box;
font-family:'Poppins',sans-serif;
}

body{
margin:0;
}

/* NAVBAR */
.premium-navbar{
position:sticky;
top:0;
z-index:1000;
display:flex;
justify-content:space-between;
align-items:center;
padding:14px 30px;
background:rgba(15,23,42,0.85);
backdrop-filter:blur(16px);
border-bottom:1px solid rgba(255,255,255,0.08);
box-shadow:0 8px 20px rgba(0,0,0,0.08);
}

/* LEFT */
.navbar-left{
display:flex;
align-items:center;
gap:18px;
}

/* MENU ICON */
.nav-toggle{
display:none;
font-size:30px;
color:white;
cursor:pointer;
}

/* BRAND */
.brand-wrap{
display:flex;
align-items:center;
gap:12px;
text-decoration:none;
}

.brand-badge{
width:44px;
height:44px;
border-radius:14px;
background:linear-gradient(135deg,#2563eb,#38bdf8);
color:white;
font-weight:700;
font-size:18px;
display:flex;
align-items:center;
justify-content:center;
box-shadow:0 6px 18px rgba(37,99,235,0.35);
}

.brand-info{
display:flex;
flex-direction:column;
}

.brand-title{
font-size:14px;
font-weight:700;
color:white;
letter-spacing:0.4px;
}

.brand-tagline{
font-size:10px;
color:#cbd5e1;
}

/* DESKTOP MENU */
.desktop-menu{
display:flex;
gap:28px;
align-items:center;
}

.desktop-menu a{
color:white;
text-decoration:none;
font-size:14px;
font-weight:500;
transition:0.3s;
position:relative;
}

.desktop-menu a:hover{
color:#38bdf8;
}

/* MOBILE MENU */
.mobile-menu{
position:fixed;
top:0;
left:-100%;
width:300px;
height:100vh;
background:rgba(15,23,42,0.98);
backdrop-filter:blur(18px);
padding:25px 20px;
transition:0.4s ease;
z-index:2000;
display:flex;
flex-direction:column;
gap:18px;
box-shadow:8px 0 25px rgba(0,0,0,0.25);
}

.mobile-menu.active{
left:0;
}

.mobile-header{
display:flex;
justify-content:space-between;
align-items:center;
margin-bottom:20px;
}

.close-btn{
font-size:30px;
color:white;
cursor:pointer;
}

.mobile-menu a{
color:white;
text-decoration:none;
font-size:16px;
padding:12px 10px;
border-radius:12px;
transition:0.3s;
}

.mobile-menu a:hover{
background:rgba(255,255,255,0.06);
color:#38bdf8;
}

/* RESPONSIVE */
@media(max-width:900px){

.desktop-menu{
display:none;
}

.nav-toggle{
display:block;
}

.premium-navbar{
padding:14px 20px;
}

.brand-title{
font-size:13px;
}

.brand-tagline{
font-size:9px;
}

.brand-badge{
width:40px;
height:40px;
font-size:16px;
}

}

/* =========================
FOOTER CSS
========================= */

.site-footer{
text-align:center;
padding:18px 20px;
background:rgba(15,23,42,0.92);
backdrop-filter:blur(10px);
border-top:1px solid rgba(255,255,255,0.06);
margin-top:60px;
}

.site-footer p{
margin:0;
font-size:14px;
color:#cbd5e1;
letter-spacing:0.4px;
font-weight:500;
}

/* Mobile Responsive */
@media(max-width:768px){
.site-footer{
padding:16px 12px;
}

.site-footer p{
font-size:12px;
}
}


h1{
text-align:center;
font-size:32px;
margin-bottom:10px;
}
.subtitle{
text-align:center;
color:#cbd5e1;
margin-bottom:30px;
}
.lock-box{
background:rgba(255,255,255,0.05);
padding:25px;
border-radius:20px;
text-align:center;
margin-bottom:30px;
}
input{
padding:14px;
width:250px;
border:none;
border-radius:10px;
margin-right:10px;
margin: 5px;
}
button{
padding:14px 20px;
border:none;
border-radius:10px;
background:linear-gradient(135deg,#2563eb,#38bdf8);
color:white;
font-weight:bold;
cursor:pointer;
}
.pass-class{
    position:absolute;
left:-9999px;
opacity:0;
pointer-events:none;
height:0;
width:0;
border:none;
}
.paper-section{
display:block;
}
.paper-card{
background:rgba(255,255,255,0.05);
padding:20px;
border-radius:18px;
margin-bottom:20px;
}
.paper-card h3{
margin-top:0;
}
.links a{
display:inline-block;
margin:10px 10px 0 0;
padding:12px 18px;
background:#1e293b;
color:white;
text-decoration:none;
border-radius:10px;
}
.links a:hover{
background:#2563eb;
}
.note{
margin-top:15px;
color:#fbbf24;
font-size:14px;
}



/* ================= DOWNLOAD / WATCH BUTTONS ================= */

.btn{
display:inline-flex;
align-items:center;
gap:8px;
margin:10px 10px 0 0;
padding:12px 20px;
border:none;
border-radius:12px;
font-family:'Poppins',sans-serif;
font-weight:600;
font-size:15px;
color:#fff;
text-decoration:none;
cursor:pointer;
transition:transform .2s ease, box-shadow .2s ease, filter .2s ease;
}
.btn i{font-size:18px;}
.btn:hover{transform:translateY(-2px);filter:brightness(1.08);}
.btn:active{transform:translateY(0);}

.links a.btn-download,.btn-download{
background:linear-gradient(135deg,#2563eb,#1e3a8a);
box-shadow:0 8px 22px rgba(37,99,235,.35);
}
.links a.btn-watch,.btn-watch{
background:linear-gradient(135deg,#dc2626,#991b1b);
box-shadow:0 8px 22px rgba(220,38,38,.35);
}

/* ================= AD OVERLAY ================= */

.ad-overlay{
display:none;
position:fixed;
inset:0;
z-index:9999;
background:rgba(2,6,23,.78);
backdrop-filter:blur(4px);
padding:20px;
align-items:center;
justify-content:center;
}
.ad-overlay.active{display:flex;}

.ad-overlay-box{
width:100%;
max-width:480px;
background:#0f172a;
border:1px solid rgba(255,255,255,.08);
border-radius:20px;
padding:18px;
box-shadow:0 24px 60px rgba(0,0,0,.5);
}
.ad-overlay-head{
display:flex;
align-items:center;
justify-content:space-between;
gap:12px;
margin-bottom:14px;
}
.ad-overlay-label{
font-size:12px;
letter-spacing:1px;
text-transform:uppercase;
color:#94a3b8;
}
.close-ads-btn{
display:inline-flex;
align-items:center;
gap:6px;
background:#16a34a;
color:#fff;
border:none;
padding:10px 16px;
border-radius:40px;
font-family:'Poppins',sans-serif;
font-weight:600;
font-size:14px;
cursor:pointer;
box-shadow:0 8px 20px rgba(22,163,74,.35);
transition:transform .2s ease, filter .2s ease;
}
.close-ads-btn i{font-size:18px;}
.close-ads-btn:hover{transform:translateY(-2px);filter:brightness(1.08);}
.ad-overlay-box .adsbygoogle{min-height:120px;}
.ad-overlay-note{
margin:14px 0 0;
text-align:center;
font-size:13px;
color:#cbd5e1;
}

/* MOBILE */
@media(max-width:768px){
.ad-overlay-head{flex-direction:column;align-items:stretch;text-align:center;}
.close-ads-btn{justify-content:center;}
.btn{width:100%;justify-content:center;margin-right:0;}
}
/* ── Click-to-reveal solutions button ─────────────────────── */
.reveal-wrap { text-align: center; margin: 26px 0; }
.reveal-btn {
  font-family: 'Poppins', sans-serif;
  font-weight: 600;
  font-size: 16px;
  cursor: pointer;
  background: #16a34a;
  color: #fff;
  border: none;
  padding: 15px 32px;
  border-radius: 40px;
  box-shadow: 0 8px 24px rgba(22,163,74,.35);
  transition: transform .2s ease, box-shadow .2s ease;
}
.reveal-btn:hover { transform: translateY(-2px); box-shadow: 0 12px 30px rgba(22,163,74,.45); }
.reveal-btn:active { transform: translateY(0); }

/* ---------- Footer legal links ---------- */
.footer-legal { display: flex; flex-wrap: wrap; justify-content: center; gap: 8px 22px; padding: 18px 5% 4px; font-size: 0.85rem; }
.footer-legal a { color: rgba(238,240,246,0.65); text-decoration: none; }
.footer-legal a:hover { color: #a3e635; }

/* ---------- Breadcrumb + related resources ---------- */
.crumbs { font-size: 13px; color: #94a3b8; margin: 4px 0 18px; }
.crumbs a { color: #38bdf8; text-decoration: none; }
.related-res { margin-top: 44px; }
.related-res h2 { font-size: 22px; margin-bottom: 16px; text-align: left; }
.related-res h3 { font-size: 17px; margin: 26px 0 12px; color: #e2e8f0; text-transform: capitalize; }
.related-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 14px; }
.related-card { display: flex; flex-direction: column; gap: 4px; padding: 18px; border-radius: 16px; background: rgba(255,255,255,0.05); border: 1px solid rgba(255,255,255,0.08); color: #fff; text-decoration: none; transition: transform .2s ease, background .2s ease; }
.related-card:hover { transform: translateY(-3px); background: rgba(56,189,248,0.10); }
.related-card span { font-size: 13px; color: #94a3b8; }
.related-links { display: flex; flex-wrap: wrap; gap: 10px; }
.related-links a { padding: 8px 14px; border-radius: 999px; background: rgba(255,255,255,0.05); border: 1px solid rgba(255,255,255,0.08); color: #cbd5e1; text-decoration: none; font-size: 14px; }
.related-links a:hover { color: #38bdf8; border-color: rgba(56,189,248,0.4); }

/* ---------- Solved paper videos (click to play) ---------- */
.video-sol { margin-top: 40px; }
.video-sol h2 { font-size: 22px; text-align: left; margin-bottom: 16px; }
.lite-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 18px; }
.lite-item { display: flex; flex-direction: column; gap: 8px; }
.lite-item a { color: #cbd5e1; text-decoration: none; font-size: 14px; line-height: 1.4; }
.lite-item a:hover { color: #38bdf8; }
.lite-yt, .lite-item iframe { position: relative; display: block; width: 100%; aspect-ratio: 16 / 9; border: 0; border-radius: 14px; overflow: hidden; background: #000; cursor: pointer; padding: 0; }
.lite-yt img { width: 100%; height: 100%; object-fit: cover; display: block; opacity: .9; transition: opacity .2s ease; }
.lite-yt:hover img { opacity: 1; }
.lite-yt:focus-visible { outline: 2px solid #38bdf8; outline-offset: 3px; }
.lite-play { position: absolute; left: 50%; top: 50%; transform: translate(-50%, -50%); width: 64px; height: 44px; border-radius: 12px; background: #dc2626; color: #fff; font-size: 20px; display: grid; place-items: center; box-shadow: 0 8px 22px rgba(0,0,0,.4); }
.video-sol-more a { display: inline-block; margin-top: 16px; color: #38bdf8; font-weight: 600; text-decoration: none; }


/* ---------- Readability & touch targets (phones) ---------- */
@media (max-width: 640px) {
  .footer-links-col a, .footer-col a { display: block; padding: 9px 0; }
  .footer-legal a { display: inline-block; padding: 10px 6px; }
  .paper-breadcrumb a, .crumbs a { display: inline-block; padding: 8px 2px; }
  .sem-table td a, .info-link, .video-sol-more a { display: inline-block; padding: 8px 0; }
  .hstat-l, .stat-label, .lstat-l, .sband-label, .pl-cat, .pl-badge, .donate-label, .note-type-tag,
  .dl-badge, .contribute-badge, .avatar-badge, .info-tag, .brand-tagline, .lec-ad-label, .ad-label { font-size: 12px !important; }
}
@media (max-width: 640px) { .lite-item a { padding: 6px 0; } }

/* ---------- Menu: switch to ☰ below 1150px (more menu items now) ---------- */
@media (max-width: 1150px) { .desktop-menu { display: none; } .nav-toggle { display: block; } }