:root{
  --bg:#ffffff;
  --ink:#0a0a0a;
  --ink-soft:#5c5c5c;
  --ink-faint:#9a9a9a;
  --line:#e6e6e6;
  --surface:#f7f7f7;
  --accent:#1d4ed8;
  --accent-soft:#eaf0fd;
  --radius:12px;
  --maxw:1120px;
}
*{box-sizing:border-box;margin:0;padding:0;}
html{scroll-behavior:smooth;}
body{
  font-family:'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI',Arial,sans-serif;
  color:var(--ink);
  background:var(--bg);
  line-height:1.6;
  -webkit-font-smoothing:antialiased;
}
a{color:inherit;text-decoration:none;}
img{max-width:100%;display:block;}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 24px;}

/* Header */
header{
  position:sticky;top:0;z-index:50;
  background:rgba(255,255,255,0.9);
  backdrop-filter:blur(8px);
  border-bottom:1px solid var(--line);
}
.nav{
  display:flex;align-items:center;justify-content:space-between;
  height:72px;
}
.logo img{height:70px;width:auto;display:block;}
.nav-links{display:flex;gap:32px;font-size:14px;color:var(--ink-soft);}
.nav-links a:hover{color:var(--ink);}
.nav-cta{
  font-size:14px;font-weight:500;
  padding:10px 20px;border-radius:999px;
  background:var(--ink);color:#fff;
}
.nav-toggle{display:none;background:none;border:none;cursor:pointer;padding:8px;}
.nav-toggle span{display:block;width:22px;height:2px;background:var(--ink);margin:5px 0;}

/* Hero */
.hero{padding:96px 0 72px;text-align:center;}
.eyebrow{
  font-size:12px;letter-spacing:0.12em;color:var(--ink-faint);
  text-transform:uppercase;margin-bottom:20px;
}
h1{
  font-size:clamp(32px,5vw,52px);
  font-weight:600;line-height:1.2;letter-spacing:-0.01em;
  margin-bottom:20px;
}
h1 .accent{color:var(--accent);}
.hero p{max-width:520px;margin:0 auto 36px;color:var(--ink-soft);font-size:17px;}
.hero-actions{display:flex;gap:12px;justify-content:center;flex-wrap:wrap;}
.hero-visual{
  margin-top:56px;border-radius:16px;overflow:hidden;
  border:1px solid var(--line);
}
.hero-visual img{width:100%;height:440px;object-fit:cover;display:block;}
@media (max-width:640px){
  .hero-visual img{height:260px;}
}
.btn{
  padding:14px 28px;border-radius:999px;font-size:14px;font-weight:500;
  border:1px solid var(--line);
}
.btn-primary{background:var(--ink);color:#fff;border-color:var(--ink);}
.btn-secondary{background:#fff;color:var(--ink);}

/* Page header (non-hero pages) */
.page-head{padding:56px 0 40px;}
.page-head h1{font-size:clamp(26px,4vw,36px);margin-bottom:8px;}
.page-head p{color:var(--ink-soft);font-size:15px;}

/* Two big cards */
.pillars{display:grid;grid-template-columns:1fr 1fr;gap:20px;padding:0 0 80px;}
.pillar{
  background:var(--surface);border-radius:var(--radius);
  padding:40px;border:1px solid var(--line);
  transition:border-color .15s ease;
}
.pillar:hover{border-color:var(--ink-faint);}
.pillar-icon{
  width:44px;height:44px;border-radius:10px;
  background:var(--accent-soft);color:var(--accent);
  display:flex;align-items:center;justify-content:center;
  font-size:20px;margin-bottom:24px;
}
.pillar h3{font-size:20px;font-weight:600;margin-bottom:8px;}
.pillar h3 .accent{color:var(--accent);}
.pillar p{color:var(--ink-soft);font-size:14px;margin-bottom:20px;}
.pillar-link{font-size:14px;font-weight:500;color:var(--ink);}
.pillar-link .arrow{color:var(--accent);margin-left:4px;}

/* Section heading */
.section-head{display:flex;align-items:baseline;justify-content:space-between;margin-bottom:28px;}
.section-head h2{font-size:22px;font-weight:600;}
.section-head a{font-size:13px;color:var(--ink-soft);}

/* Articles */
.articles{padding:0 0 96px;}
.article-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;}
.article-card{border:1px solid var(--line);border-radius:var(--radius);padding:22px;}
.article-tag{font-size:11px;color:var(--ink-faint);text-transform:uppercase;letter-spacing:0.06em;margin-bottom:10px;}
.article-card h4{font-size:15px;font-weight:600;line-height:1.4;margin-bottom:8px;}
.article-card h4 .accent{color:var(--accent);}
.article-card p{font-size:13px;color:var(--ink-soft);}

/* Services strip */
.services{background:var(--surface);padding:80px 0;border-top:1px solid var(--line);border-bottom:1px solid var(--line);}
.services h2{font-size:22px;font-weight:600;margin-bottom:8px;}
.services > .wrap > p{color:var(--ink-soft);font-size:14px;margin-bottom:40px;}
.steps{display:grid;grid-template-columns:repeat(4,1fr);gap:24px;}
.step-num{
  width:28px;height:28px;border-radius:50%;
  background:var(--accent-soft);color:var(--accent);
  display:flex;align-items:center;justify-content:center;
  font-size:12px;font-weight:600;margin-bottom:14px;
}
.step h4{font-size:14px;font-weight:600;margin-bottom:6px;}
.step p{font-size:13px;color:var(--ink-soft);}

/* Library layout (Teknik Kütüphane) */
.library{padding:0 0 96px;}
.library-layout{display:grid;grid-template-columns:200px 1fr;gap:32px;align-items:start;}
.search-box{position:relative;margin-bottom:24px;grid-column:1/-1;}
.search-box input{
  width:100%;padding:12px 16px 12px 40px;border:1px solid var(--line);
  border-radius:999px;font-size:14px;font-family:inherit;color:var(--ink);
}
.search-box input:focus{outline:none;border-color:var(--accent);}
.search-icon{position:absolute;left:16px;top:50%;transform:translateY(-50%);color:var(--ink-faint);font-size:14px;}
.categories{display:flex;flex-direction:column;gap:2px;}
.cat-btn{
  text-align:left;padding:10px 12px;border-radius:8px;font-size:13px;
  color:var(--ink-soft);background:none;border:none;font-family:inherit;cursor:pointer;
}
.cat-btn.active{background:var(--accent-soft);color:var(--accent);font-weight:500;}
.cat-btn:hover:not(.active){background:var(--surface);}
.lib-list{display:flex;flex-direction:column;gap:2px;}
.lib-card{
  border-bottom:1px solid var(--line);
  padding:14px 4px;display:flex;gap:14px;align-items:center;
}
.lib-thumb{
  width:40px;height:40px;flex-shrink:0;border-radius:6px;
  background:var(--surface);overflow:hidden;
}
.lib-thumb img{width:100%;height:100%;object-fit:cover;display:block;}
.lib-text{flex:1;min-width:0;}
.lib-card h4{font-size:14px;font-weight:600;margin-bottom:4px;}
.lib-card p{font-size:12px;color:var(--ink-soft);}
.lib-card .article-tag{margin-bottom:4px;}
@media (max-width:480px){
  .lib-thumb{width:36px;height:36px;}
}
.no-results{color:var(--ink-faint);font-size:14px;padding:24px 0;display:none;}

/* Footer */
footer{padding:64px 0 40px;}
.footer-top{
  display:grid;grid-template-columns:2fr 1fr 1fr;gap:40px;
  padding-bottom:40px;border-bottom:1px solid var(--line);margin-bottom:24px;
}
.footer-logo{font-weight:600;margin-bottom:12px;}
.footer-top p{color:var(--ink-soft);font-size:13px;}
.footer-col h5{font-size:12px;text-transform:uppercase;letter-spacing:0.06em;color:var(--ink-faint);margin-bottom:14px;}
.footer-col a{display:block;font-size:13px;color:var(--ink-soft);margin-bottom:10px;}
.footer-col a:hover{color:var(--ink);}
.footer-bottom{
  display:flex;justify-content:space-between;align-items:center;
  font-size:12px;color:var(--ink-faint);flex-wrap:wrap;gap:12px;
}

/* Article pages */
.article-page{max-width:680px;margin:0 auto;padding:56px 24px 96px;text-align:left;}
.article-back{font-size:13px;color:var(--ink-soft);margin-bottom:20px;display:inline-block;}
.article-category-pill{display:inline-block;background:var(--accent-soft);color:var(--accent);font-size:12px;font-weight:500;padding:4px 12px;border-radius:999px;margin-bottom:16px;}
.article-page h1{font-size:22px;font-weight:600;margin-bottom:8px;line-height:1.3;}
.article-page .article-sub{font-size:12px;color:var(--ink-faint);margin-bottom:32px;}
.article-content h2{font-size:17px;font-weight:600;margin:32px 0 10px;}
.article-content h3{font-size:14px;font-weight:600;margin:20px 0 6px;}
.article-content p{color:var(--ink-soft);font-size:14px;margin-bottom:12px;}
.article-content ul, .article-content ol{margin:0 0 12px 20px;color:var(--ink-soft);font-size:14px;}
.article-content li{margin-bottom:5px;}
.article-content strong{color:var(--ink);font-weight:600;}
.article-content code{background:var(--surface);padding:2px 6px;border-radius:4px;font-family:monospace;font-size:12px;}
.formula-block{display:block;background:var(--surface);padding:12px 16px;border-radius:8px;font-family:monospace;font-size:12px;margin:10px 0;overflow-x:auto;}
.article-thumb{border-radius:16px;overflow:hidden;border:1px solid var(--line);margin-bottom:32px;}
.article-thumb img{width:100%;height:280px;object-fit:cover;display:block;}
.callout{border-radius:12px;padding:16px 20px;margin:18px 0;font-size:14px;}
.callout p{margin-bottom:0;font-size:14px;}
.callout p + p{margin-top:8px;}
.callout-gray{background:var(--surface);color:var(--ink-soft);}
.callout-blue{background:var(--accent-soft);color:var(--accent);}
.callout-blue strong{color:var(--accent);}
.article-content table{width:100%;border-collapse:collapse;font-size:12px;margin:16px 0;}
.article-content th, .article-content td{padding:8px 10px;border-bottom:1px solid var(--line);text-align:left;}
.article-content thead th{color:var(--ink-faint);font-weight:500;font-size:10px;text-transform:uppercase;letter-spacing:0.04em;}
.article-content table + h2, .article-content table + h3{margin-top:28px;}
@media (max-width:640px){ .article-thumb img{height:180px;} }

/* Calculator pages */
.calc-layout{display:grid;grid-template-columns:1fr 1fr;gap:32px;align-items:start;padding:0 0 96px;}
.calc-field{margin-bottom:16px;}
.calc-field label{display:block;font-size:13px;color:var(--ink-soft);margin-bottom:6px;}
.calc-field input, .calc-field select{
  width:100%;padding:10px 14px;border:1px solid var(--line);
  border-radius:8px;font-size:14px;font-family:inherit;color:var(--ink);background:#fff;
}
.calc-field input:focus, .calc-field select:focus{outline:none;border-color:var(--accent);}
.calc-row{display:grid;grid-template-columns:1fr 1fr;gap:12px;}
.calc-btn{
  width:100%;padding:14px;border-radius:999px;background:var(--ink);color:#fff;
  border:none;font-size:14px;font-weight:500;cursor:pointer;margin-top:4px;
}
.calc-btn:hover{opacity:0.9;}
.calc-results{background:var(--accent-soft);border-radius:16px;padding:24px;}
.calc-result-row{display:flex;justify-content:space-between;align-items:center;padding:10px 0;border-bottom:1px solid rgba(0,0,0,0.06);}
.calc-result-row:last-child{border-bottom:none;}
.calc-result-label{font-size:13px;color:var(--ink-soft);}
.calc-result-value{font-size:15px;font-weight:600;color:var(--ink);}
.calc-result-value.big{font-size:22px;color:var(--accent);}
.status-badge{font-size:12px;font-weight:600;padding:4px 12px;border-radius:999px;}
.status-ok{background:#dcfce7;color:#166534;}
.status-error{background:#fee2e2;color:#991b1b;}
@media (max-width:860px){ .calc-layout{grid-template-columns:1fr;} }

.footer-social{display:flex;gap:10px;margin-top:6px;}
.footer-social a{
  width:36px;height:36px;border-radius:8px;background:var(--surface);
  display:flex;align-items:center;justify-content:center;
  color:var(--ink-soft);transition:background .15s ease,color .15s ease;
}
.footer-social a:hover{background:var(--accent-soft);color:var(--accent);}
.footer-social svg{width:16px;height:16px;}

/* Mobile */
@media (max-width:860px){
  .pillars{grid-template-columns:1fr;}
  .article-grid{grid-template-columns:1fr;}
  .steps{grid-template-columns:1fr 1fr;}
  .footer-top{grid-template-columns:1fr;}
  .library-layout{grid-template-columns:1fr;}
  .categories{flex-direction:row;flex-wrap:wrap;}
}
@media (max-width:640px){
  .nav-links{
    display:none;position:absolute;top:72px;left:0;right:0;
    background:#fff;flex-direction:column;padding:20px 24px;
    border-bottom:1px solid var(--line);gap:16px;z-index:40;
  }
  .nav-links.nav-open{display:flex;}
  .nav-toggle{display:block;}
  .hero{padding:64px 0 48px;}
  .steps{grid-template-columns:1fr;}
}