:root{
  --navy:#0b1e3a; --navy2:#12294d; --amber:#f5a623; --amber2:#ffcf6b;
  --bg:#f4f6fb; --card:#ffffff; --text:#1c2433; --muted:#667085;
  --radius:16px;
}
*{box-sizing:border-box}
body{margin:0;font-family:'Segoe UI',system-ui,-apple-system,Arial,sans-serif;background:var(--bg);color:var(--text);line-height:1.6}
a{color:inherit}
.container{max-width:1150px;margin:0 auto;padding:0 18px}
/* header */
.topbar{background:var(--navy);color:#fff;position:sticky;top:0;z-index:50;box-shadow:0 2px 12px rgba(0,0,0,.25)}
.topbar .container{display:flex;align-items:center;justify-content:space-between;padding:12px 18px}
.brand{display:flex;align-items:center;gap:12px;text-decoration:none}
.brand .logo{width:46px;height:46px;border-radius:50%;background:radial-gradient(circle at 30% 30%,var(--amber2),var(--amber) 60%,#b96a00);display:flex;align-items:center;justify-content:center;font-size:26px;font-weight:800;color:var(--navy)}
.brand b{font-size:20px;letter-spacing:.3px}
.brand small{display:block;color:#c8d3e8;font-weight:400;font-size:12px}
nav.menu{display:flex;gap:6px;flex-wrap:wrap}
nav.menu a{color:#dbe4f5;text-decoration:none;padding:8px 12px;border-radius:10px;font-size:15px}
nav.menu a:hover,nav.menu a.active{background:rgba(245,166,35,.18);color:#fff}
.hamburger{display:none;background:var(--amber);border:0;border-radius:10px;padding:8px 12px;font-size:20px;cursor:pointer}
/* hero + slider */
.hero{background:linear-gradient(135deg,var(--navy) 0%,var(--navy2) 60%,#1b3a6b 100%);color:#fff;padding:34px 0 46px;position:relative;overflow:hidden}
.hero::before{content:'E=mc²  F=ma  λ  Ω  Δ  Σ  π';position:absolute;right:10px;top:8px;opacity:.12;font-size:22px;letter-spacing:6px}
.slider{position:relative;background:rgba(255,255,255,.06);border:1px solid rgba(255,255,255,.15);border-radius:20px;overflow:hidden;min-height:340px}
.slide{display:none;grid-template-columns:1.1fr .9fr;gap:10px;align-items:center;padding:26px}
.slide.active{display:grid;animation:fade .6s ease}
@keyframes fade{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:none}}
.slide h2{margin:0 0 10px;font-size:30px;line-height:1.25}
.slide h2 span{color:var(--amber)}
.slide p{color:#d5ddf0;margin:0 0 18px}
.slide img{width:100%;height:260px;object-fit:cover;border-radius:14px;background:#0a1730}
.btn{display:inline-block;background:var(--amber);color:#231600;font-weight:700;text-decoration:none;padding:11px 20px;border-radius:12px;border:0;cursor:pointer}
.btn:hover{background:var(--amber2)}
.btn.ghost{background:transparent;color:#fff;border:1.5px solid rgba(255,255,255,.5)}
.dots{position:absolute;bottom:12px;left:0;right:0;display:flex;gap:8px;justify-content:center}
.dots button{width:12px;height:12px;border-radius:50%;border:0;background:rgba(255,255,255,.4);cursor:pointer;padding:0}
.dots button.on{background:var(--amber)}
.arrow{position:absolute;top:50%;transform:translateY(-50%);background:rgba(0,0,0,.35);color:#fff;border:0;width:38px;height:38px;border-radius:50%;cursor:pointer;font-size:18px}
.arrow.prev{left:10px}.arrow.next{right:10px}
.stats{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin-top:18px}
.stat{background:rgba(255,255,255,.08);border:1px solid rgba(255,255,255,.12);border-radius:14px;padding:14px;text-align:center}
.stat b{font-size:26px;color:var(--amber)}
.stat span{color:#cdd6ea;font-size:13px}
/* sections - her bolum farkli pastel zemin (okunurluluk korunur, kartlar beyaz kalir) */
section{padding:30px 22px;margin:26px 0;border-radius:22px;border:1px solid rgba(11,30,58,.07)}
section#hakkimda{background:#e8f3fd;border-color:#bcd9f5}
section#kitaplar{background:#fef6e5;border-color:#f5dcae}
section#videolar{background:#f1eaff;border-color:#d3c2f5}
section#duyurular{background:#e9f9ef;border-color:#b9e6c6}
section#testler{background:#ffeff2;border-color:#f5c2cc}
section#simulasyonlar{background:#e6f7f5;border-color:#a9e3da}
section#iletisim{background:#edf0ff;border-color:#c3cdf5}
.sim-frame{width:100%;height:230px;border:0;border-radius:12px 12px 0 0;background:#0b1e3a}
.sec-title{text-align:center;margin-bottom:8px}
.sec-title h2{margin:0;font-size:28px;color:var(--navy)}
.sec-title h2::after{content:'';display:block;width:64px;height:4px;background:var(--amber);margin:10px auto 0;border-radius:4px}
.sec-title p{color:var(--muted)}
.grid{display:grid;gap:16px}
.books{grid-template-columns:repeat(auto-fill,minmax(240px,1fr))}
.card{background:var(--card);border-radius:var(--radius);overflow:hidden;box-shadow:0 6px 20px rgba(11,30,58,.08);display:flex;flex-direction:column}
.card img{width:100%;height:300px;object-fit:cover;background:#e9edf5}
.card .body{padding:14px;display:flex;flex-direction:column;gap:8px;flex:1}
.badge{display:inline-block;background:#eef3ff;color:var(--navy);font-size:12px;font-weight:700;padding:3px 10px;border-radius:20px;width:fit-content}
.card h3{margin:0;font-size:16px}
.card p{margin:0;color:var(--muted);font-size:14px;flex:1}
.videos{grid-template-columns:repeat(auto-fill,minmax(300px,1fr))}
.video-card iframe{width:100%;height:180px;border:0;border-radius:12px 12px 0 0;background:#000}
.announce{background:linear-gradient(180deg,#fff8e8,#fff);border:1.5px dashed var(--amber);border-radius:var(--radius);padding:16px;margin-bottom:12px}
.announce h3{margin:0 0 6px;color:var(--navy)}
.announce small{color:var(--muted)}
.about{display:flex;gap:26px;align-items:flex-start;background:var(--card);border-radius:20px;padding:24px;box-shadow:0 6px 20px rgba(11,30,58,.08)}
.about>div:first-child{flex:0 0 220px;min-width:0}
.about>div:last-child{flex:1;min-width:0;overflow-wrap:break-word;word-break:break-word}
.about p{margin:0 0 12px}
.avatar{width:100%;max-width:220px;height:260px;border-radius:16px;background:linear-gradient(160deg,var(--navy),#2c5aa0);color:#fff;display:flex;flex-direction:column;align-items:center;justify-content:center;font-size:64px}
.avatar small{font-size:14px;color:var(--amber2)}
.profile-photo{width:100%;max-width:220px;height:260px;object-fit:cover;object-position:top center;border-radius:16px;box-shadow:0 6px 20px rgba(11,30,58,.15);background:#e9edf5;display:block}
form.contact{background:var(--card);border-radius:var(--radius);padding:20px;box-shadow:0 6px 20px rgba(11,30,58,.08);display:grid;gap:10px}
input,textarea,select{width:100%;padding:11px 12px;border:1.5px solid #d7deea;border-radius:10px;font-size:15px;font-family:inherit}
input:focus,textarea:focus,select:focus{outline:none;border-color:var(--amber)}
label{font-weight:600;font-size:14px}
.two{display:grid;grid-template-columns:1fr 1fr;gap:10px}
.tests{grid-template-columns:repeat(auto-fill,minmax(280px,1fr))}
footer{background:var(--navy);color:#c9d4ea;padding:26px 0;margin-top:20px;text-align:center;font-size:14px}
footer a{color:var(--amber2)}
.filter-bar{display:flex;gap:8px;flex-wrap:wrap;justify-content:center;margin:16px 0}
.filter-bar button{border:1.5px solid #c9d4ea;background:#fff;padding:7px 14px;border-radius:20px;cursor:pointer;font-size:14px}
.filter-bar button.on{background:var(--navy);color:#fff;border-color:var(--navy)}
.alert{padding:12px 14px;border-radius:10px;margin:12px 0}
.alert.ok{background:#e6f7ea;color:#14532d}
.alert.err{background:#fde8e8;color:#7f1d1d}
.question{background:#fff;border-radius:12px;padding:14px;margin-bottom:12px;box-shadow:0 2px 8px rgba(0,0,0,.06)}
.question label{display:block;font-weight:400;margin:6px 0;cursor:pointer}
@media(max-width:820px){
  section{padding:22px 14px;margin:18px 0}
  .slide{grid-template-columns:1fr}
  .slide img{height:200px}
  nav.menu{display:none;width:100%;flex-direction:column;margin-top:10px}
  nav.menu.open{display:flex}
  .hamburger{display:block}
  .about{flex-direction:column}
  .about>div:first-child{flex:none;max-width:280px}
  .avatar{width:100%;height:180px}
  .profile-photo{width:100%;height:220px}
  .two{grid-template-columns:1fr}
  .stats{grid-template-columns:1fr 1fr 1fr}
  .slide h2{font-size:22px}
}