/* BSN-Tax web sitesi: ortak stiller. Renk ve yazı değerleri docs/tasarim/landing/BRIEF.md §6 ile aynı. */
:root {
  --zemin: #F7F6F3; --yuzey: #FFFFFF; --metin: #1A1D21; --ikincil: #33383F; --soluk: #5A6068;
  --cizgi: #E4E1DA; --cizgi-ince: #EFEDE8; --cizgi-koyu: #CFCBC2;
  --petrol: #1F4E5F; --petrol-koyu: #16394A; --petrol-orta: #9FBCC6; --petrol-acik: #EAF0F2;
  --serif: 'Source Serif 4', Georgia, serif; --sans: 'IBM Plex Sans', system-ui, sans-serif; --mono: 'IBM Plex Mono', ui-monospace, monospace;
}
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--zemin); color: var(--metin); font-family: var(--sans); -webkit-font-smoothing: antialiased; overflow-x: hidden; }
a { color: var(--petrol); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { color: var(--petrol-koyu); }
button { font-family: inherit; }
img, svg { max-width: 100%; }
:focus-visible { outline: 2px solid var(--petrol); outline-offset: 2px; }
[id] { scroll-margin-top: 72px; }

/* Masaüstü / mobil ayrımı (canvas'taki isDesktop = genişlik >= 880) */
@media (max-width: 879.98px) { .d-only { display: none !important; } }
@media (min-width: 880px) { .m-only { display: none !important; } }

/* Header */
.site-header { position: sticky; top: 0; z-index: 50; background: rgba(247,246,243,0.94); backdrop-filter: blur(8px); -webkit-backdrop-filter: blur(8px); border-bottom: 1px solid var(--cizgi); }
.site-header__in { max-width: 1200px; margin: 0 auto; padding: 0 clamp(16px,4vw,40px); height: 64px; display: flex; align-items: center; justify-content: space-between; gap: 24px; }
.logo { display: flex; align-items: center; gap: 10px; text-decoration: none; min-height: 44px; }
.logo__bsn { font: 600 21px/1 var(--serif); letter-spacing: 0.4px; color: var(--petrol-koyu); }
.logo__cizgi { width: 1px; height: 16px; background: var(--petrol-orta); }
.logo__tax { font: 500 12px/1 var(--mono); letter-spacing: 2.4px; color: var(--petrol); }
.nav { display: flex; align-items: center; gap: 28px; font-size: 15px; }
.nav a { color: var(--metin); text-decoration: none; }
.nav a:hover { color: var(--petrol); }
.nav a[aria-current="page"] { color: var(--petrol); text-decoration: underline; text-decoration-thickness: 2px; text-underline-offset: 8px; font-weight: 500; }
.header-actions { display: flex; align-items: center; gap: 20px; }
.header-actions__giris { color: var(--metin); text-decoration: none; font-size: 15px; }
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: 44px; padding: 0 18px; border-radius: 6px; font: 600 15px/1 var(--sans); text-decoration: none; cursor: pointer; border: 1px solid transparent; }
.btn--birincil { background: var(--petrol); color: #FFFFFF; }
.btn--birincil:hover { background: var(--petrol-koyu); color: #FFFFFF; }
.btn--ikincil { border-color: var(--petrol); color: var(--petrol); background: transparent; }
.btn--ikincil:hover { background: var(--petrol-acik); color: var(--petrol-koyu); }
.menu-btn { width: 44px; height: 44px; border: 1px solid var(--cizgi); background: #FFFFFF; border-radius: 6px; display: grid; place-items: center; cursor: pointer; color: var(--metin); padding: 0; }
.menu-btn .ikon-kapat { display: none; }
.menu-btn[aria-expanded="true"] .ikon-ac { display: none; }
.menu-btn[aria-expanded="true"] .ikon-kapat { display: block; }
.mobil-menu { border-top: 1px solid var(--cizgi); background: var(--zemin); padding: 8px 16px 16px; flex-direction: column; display: none; }
.mobil-menu.acik { display: flex; }
.mobil-menu a { color: var(--metin); text-decoration: none; font-size: 17px; padding: 14px 0; border-bottom: 1px solid var(--cizgi); }
.mobil-menu a:last-child { border-bottom: 0; }
.mobil-menu a[aria-current="page"] { color: var(--petrol); }
@media (min-width: 880px) { .mobil-menu, .mobil-menu.acik { display: none; } }

/* Footer */
.site-footer { background: #FFFFFF; border-top: 1px solid var(--cizgi); }
.site-footer__ust { max-width: 1200px; margin: 0 auto; padding: clamp(48px,6vw,72px) clamp(16px,4vw,40px) 0; display: flex; flex-wrap: wrap; gap: 40px clamp(32px,5vw,64px); }
.site-footer__marka { flex: 1.4 1 280px; min-width: 0; display: flex; flex-direction: column; gap: 18px; max-width: 360px; }
.site-footer__marka p { margin: 0; font-size: 15px; line-height: 1.6; color: var(--soluk); }
.guvenceler { margin: 0; padding: 0; list-style: none; display: flex; flex-direction: column; gap: 10px; }
.guvenceler li { display: flex; align-items: center; gap: 10px; font-size: 14px; color: var(--ikincil); }
.tik { flex: none; width: 20px; height: 20px; border-radius: 50%; background: #DCEBDD; color: #1E4D2B; display: grid; place-items: center; }
.footer-nav { flex: 3 1 520px; min-width: 0; display: grid; grid-template-columns: repeat(auto-fit, minmax(min(100%,150px),1fr)); gap: 32px 24px; }
.footer-nav__baslik { font: 500 12px/1 var(--mono); letter-spacing: 0.1em; text-transform: uppercase; color: var(--soluk); margin-bottom: 12px; }
.footer-nav ul { margin: 0; padding: 0; list-style: none; display: flex; flex-direction: column; gap: 2px; }
.footer-nav a { display: inline-flex; align-items: center; min-height: 36px; font-size: 15px; color: var(--metin); text-decoration: none; }
.footer-nav a:hover { color: var(--petrol); }
.footer-cta-dis { max-width: 1200px; margin: 0 auto; padding: 32px clamp(16px,4vw,40px) 0; }
.footer-cta { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 16px; background: #F2F5F6; border: 1px solid var(--cizgi); border-radius: 10px; padding: 18px 20px; }
.footer-cta strong { display: block; font: 600 17px/1.3 var(--serif); }
.footer-cta span { font-size: 14px; color: var(--soluk); }
.footer-cta__dugmeler { display: flex; flex-wrap: wrap; gap: 10px; }
.site-footer__alt { max-width: 1200px; margin: 0 auto; padding: 28px clamp(16px,4vw,40px) 32px; display: flex; flex-wrap: wrap; justify-content: space-between; gap: 12px 32px; font-size: 13px; line-height: 1.6; color: var(--soluk); }
.site-footer__alt span:last-child { max-width: 640px; }

/* SSS (details/summary ile açılır kapanır) */
.sss details { border-bottom: 1px solid var(--cizgi); }
.sss summary { list-style: none; cursor: pointer; }
.sss summary::-webkit-details-marker { display: none; }
.sss .sss-isaret::before { content: '+'; }
.sss details[open] .sss-isaret::before { content: '−'; }