/* ===== BIT Group — корпоративный лендинг ===== */
:root{
  --navy:#0d2340;        /* основной тёмно-синий */
  --navy-2:#12304f;      /* чуть светлее */
  --steel:#1f4e79;       /* стальной акцент */
  --accent:#2e77c9;      /* яркий акцент */
  --ink:#1a2432;         /* основной текст */
  --muted:#5a6b80;       /* второстепенный текст */
  --line:#e2e8f0;        /* линии/границы */
  --bg:#ffffff;
  --bg-alt:#f4f7fb;      /* фон чередующихся секций */
  --radius:14px;
  --wrap:1160px;
  --shadow:0 10px 30px rgba(13,35,64,.08);
}

*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  color:var(--ink);
  background:var(--bg);
  line-height:1.6;
  -webkit-font-smoothing:antialiased;
}
img{max-width:100%;display:block}
a{color:inherit;text-decoration:none}

.container{width:100%;max-width:var(--wrap);margin:0 auto;padding:0 24px}

/* ---- Кнопки ---- */
.btn{
  display:inline-flex;align-items:center;justify-content:center;
  padding:13px 26px;border-radius:10px;font-weight:600;font-size:15px;
  border:1.5px solid transparent;cursor:pointer;transition:.2s;white-space:nowrap;
}
.btn-primary{background:var(--accent);color:#fff}
.btn-primary:hover{background:#2668b3}
.btn-outline{border-color:rgba(255,255,255,.35);color:#fff}
.btn-outline:hover{border-color:#fff;background:rgba(255,255,255,.08)}
.btn-ghost{border-color:rgba(255,255,255,.4);color:#fff}
.btn-ghost:hover{background:rgba(255,255,255,.1)}

/* ---- Логотип ---- */
.logo{display:inline-flex;align-items:center;gap:11px}
.logo-emblem{flex:none}
.logo-text{display:flex;flex-direction:column;line-height:1}
.logo-text b{font-size:21px;font-weight:800;letter-spacing:1.5px;color:#fff}
.logo-text span{font-size:10px;letter-spacing:4px;font-weight:600;color:#8fb4dd;margin-top:3px}

/* ---- Шапка ---- */
.site-header{
  position:sticky;top:0;z-index:50;
  background:rgba(13,35,64,.96);backdrop-filter:blur(8px);
  border-bottom:1px solid rgba(255,255,255,.08);
}
.header-inner{display:flex;align-items:center;gap:28px;height:72px}
.nav{display:flex;gap:26px;margin-left:auto}
.nav a{color:#cdd8e6;font-size:15px;font-weight:500;transition:.15s}
.nav a:hover{color:#fff}
.header-contacts{display:flex;align-items:center;gap:16px}
.header-mail{color:#cdd8e6;font-size:15px;font-weight:500;transition:.15s;white-space:nowrap}
.header-mail:hover{color:#fff}
.header-phone{font-size:15px}
.burger{display:none;flex-direction:column;gap:5px;background:none;border:0;cursor:pointer;padding:6px}
.burger span{width:24px;height:2px;background:#fff;display:block;transition:.2s}

/* ---- Герой ---- */
.hero{
  background:
    radial-gradient(1200px 500px at 80% -10%, rgba(46,119,201,.35), transparent 60%),
    linear-gradient(160deg,var(--navy),var(--navy-2));
  color:#fff;padding:88px 0 72px;position:relative;overflow:hidden;
}
.hero-inner{max-width:820px}
.hero-eyebrow{text-transform:uppercase;letter-spacing:2px;font-size:13px;color:#8fb4dd;font-weight:600;margin-bottom:18px}
.hero-title{font-size:clamp(32px,5vw,52px);line-height:1.1;font-weight:800;letter-spacing:-.5px}
.hero-title .accent{color:#5aa0ec}
.hero-lead{font-size:clamp(16px,2vw,19px);color:#c6d4e6;margin:22px 0 32px;max-width:640px}
.hero-actions{display:flex;gap:14px;flex-wrap:wrap}
.hero-stats{list-style:none;display:flex;gap:44px;margin-top:56px;flex-wrap:wrap}
.hero-stats li{display:flex;flex-direction:column}
.hero-stats b{font-size:30px;font-weight:800;color:#fff;line-height:1.1}
.hero-stats span{font-size:14px;color:#9fb6d1;margin-top:4px}

/* ---- Секции ---- */
.section{padding:76px 0}
.section-alt{background:var(--bg-alt)}
.section-title{font-size:clamp(26px,3.4vw,36px);font-weight:800;letter-spacing:-.5px;color:var(--navy)}
.section-sub{color:var(--muted);font-size:17px;margin-top:10px;margin-bottom:38px}

/* ---- Сетки ---- */
.grid{display:grid;gap:22px}
.grid-4{grid-template-columns:repeat(4,1fr)}
.grid-3{grid-template-columns:repeat(3,1fr)}

/* ---- Преимущества ---- */
.feature{padding:6px 4px}
.feature-num{font-size:15px;font-weight:800;color:var(--accent);letter-spacing:1px}
.feature h3{margin:12px 0 8px;font-size:19px;color:var(--navy)}
.feature p{color:var(--muted);font-size:15px}

/* ---- Карточки услуг ---- */
.card{
  background:var(--bg);border:1px solid var(--line);border-radius:var(--radius);
  padding:28px 26px;transition:.2s;
}
.section-alt .card{background:#fff}
.card:hover{transform:translateY(-4px);box-shadow:var(--shadow);border-color:#c9d8ea}
.card-icon{font-size:30px;margin-bottom:14px}
.card h3{font-size:19px;color:var(--navy);margin-bottom:8px}
.card p{color:var(--muted);font-size:15px}

/* ---- Частые вопросы (FAQ) ---- */
.faq{max-width:840px;margin:0 auto}
.faq-item{border:1px solid var(--line);border-radius:12px;margin-bottom:12px;background:#fff;overflow:hidden;transition:.2s}
.faq-item[open]{border-color:#c9d8ea;box-shadow:var(--shadow)}
.faq-item summary{
  cursor:pointer;padding:18px 22px;font-weight:600;color:var(--navy);font-size:16px;
  list-style:none;display:flex;justify-content:space-between;align-items:center;gap:14px;
}
.faq-item summary::-webkit-details-marker{display:none}
.faq-item summary::after{content:"+";font-size:24px;line-height:1;color:var(--accent);font-weight:400;flex:none}
.faq-item[open] summary::after{content:"\2212"}
.faq-a{padding:0 22px 20px;color:var(--muted);font-size:15px;line-height:1.65}

/* ---- Страница партнёров ---- */
.page-hero{
  background:linear-gradient(160deg,var(--navy),var(--navy-2));
  color:#fff;padding:56px 0 48px;
}
.page-hero-title{font-size:clamp(28px,4vw,42px);font-weight:800;letter-spacing:-.5px;margin:14px 0 16px}
.page-hero-lead{color:#c6d4e6;font-size:17px;max-width:720px}
.brand-group{margin-bottom:46px}
.brand-group:last-of-type{margin-bottom:20px}
.brand-group .section-title{font-size:22px;margin-bottom:22px}
.brand-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:20px}
.brand-card{
  display:flex;flex-direction:column;align-items:center;gap:12px;
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  padding:24px 18px;transition:.2s;
}
.brand-card:hover{box-shadow:var(--shadow);border-color:#c9d8ea;transform:translateY(-3px)}
.brand-logo{
  width:100%;height:80px;display:flex;align-items:center;justify-content:center;
  background:var(--bg-alt);border-radius:8px;overflow:hidden;
}
.brand-logo img{max-width:82%;max-height:64px;object-fit:contain;filter:grayscale(1);opacity:.85;transition:.2s}
.brand-card:hover .brand-logo img{filter:none;opacity:1}
.brand-logo span{font-size:12px;letter-spacing:1px;color:#b0bccb;font-weight:700}
.brand-name{font-size:15px;font-weight:600;color:var(--navy);text-align:center}
@media(max-width:900px){.brand-grid{grid-template-columns:repeat(3,1fr)}}
@media(max-width:640px){.brand-grid{grid-template-columns:repeat(2,1fr)}}

/* ---- Бегущая лента партнёров ---- */
.marquee{
  display:flex;flex-direction:column;gap:16px;padding:10px 0;overflow:hidden;width:100%;
  -webkit-mask-image:linear-gradient(90deg,transparent 0,#000 7%,#000 93%,transparent 100%);
          mask-image:linear-gradient(90deg,transparent 0,#000 7%,#000 93%,transparent 100%);
}
.marquee-row{display:flex;overflow:hidden}
.marquee-track{
  display:flex;flex:0 0 auto;width:max-content;will-change:transform;
  animation:bit-scroll 64s linear infinite;
}
.marquee-row.rtl .marquee-track{animation-direction:reverse}
.marquee:hover .marquee-track{animation-play-state:paused}
@keyframes bit-scroll{from{transform:translateX(0)}to{transform:translateX(-50%)}}
.brand-chip{
  flex:0 0 auto;height:66px;min-width:158px;margin-right:16px;padding:0 30px;
  display:flex;align-items:center;justify-content:center;
  background:#fff;border:1px solid var(--line);border-radius:12px;
  font-weight:600;color:var(--navy);font-size:16px;white-space:nowrap;
  box-shadow:0 4px 14px rgba(13,35,64,.05);transition:.2s;
}
.brand-chip:hover{border-color:var(--accent);box-shadow:0 8px 22px rgba(13,35,64,.12)}
.brand-chip img{max-height:42px;max-width:118px;object-fit:contain;filter:grayscale(1);opacity:.85;transition:.2s}
.brand-chip:hover img{filter:none;opacity:1}
@media (prefers-reduced-motion: reduce){.marquee-track{animation:none}}
@media(max-width:640px){.brand-chip{height:56px;min-width:130px;padding:0 22px;font-size:15px;margin-right:12px}}

/* ---- Каталог инженерных систем ---- */
.sys-cols{display:flex;gap:22px;align-items:flex-start}
.sys-col{flex:1 1 0;display:flex;flex-direction:column;gap:22px;min-width:0}
.sys-cat{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  padding:20px 22px;
}
.sys-cat-head{display:flex;align-items:center;gap:10px;margin-bottom:8px;padding-bottom:12px;border-bottom:2px solid var(--accent)}
.sys-cat-head h3{font-size:16px;color:var(--navy);margin:0;line-height:1.2}
.sys-icon{font-size:22px;flex:none}
.sys-list{list-style:none;margin:0;padding:0}
.sys-list li{
  display:flex;gap:12px;align-items:center;
  min-height:44px;padding:6px 0;border-bottom:1px solid var(--line);font-size:14px;
}
.sys-list li:last-child{border-bottom:0}
.sys-list b{color:var(--accent);flex:none;width:88px;font-weight:700;font-size:13px}
.sys-list span{color:var(--muted)}
@media(max-width:900px){
  .sys-cols{flex-wrap:wrap}
  .sys-col{flex:1 1 46%}
}
@media(max-width:640px){.sys-col{flex:1 1 100%}}

/* ---- Направления (крупные карточки) ---- */
.card-pillar{padding:32px 28px}
.card-pillar .card-icon{font-size:34px}

/* ---- Холдинг ---- */
.holding-card{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  padding:26px 24px;transition:.2s;
}
.holding-card:hover{box-shadow:var(--shadow);transform:translateY(-3px)}
.holding-card--accent{background:var(--navy);border-color:var(--navy)}
.holding-card--accent h3,.holding-card--accent p{color:#fff}
.holding-card--accent p{color:#c6d4e6}
.holding-badge{
  display:inline-block;font-size:12px;font-weight:700;text-transform:uppercase;
  letter-spacing:1px;color:var(--accent);background:#eaf2fc;
  padding:4px 12px;border-radius:20px;margin-bottom:14px;
}
.holding-card--accent .holding-badge{color:#fff;background:rgba(255,255,255,.16)}
.holding-card h3{font-size:18px;color:var(--navy);margin-bottom:8px}
.holding-card p{font-size:14px;color:var(--muted)}

/* ---- Проекты ---- */
.tag-card{
  border-left:3px solid var(--accent);background:var(--bg-alt);
  padding:22px 24px;border-radius:0 var(--radius) var(--radius) 0;
}
.section .tag-card{background:var(--bg-alt)}
.tag-card h3{font-size:18px;color:var(--navy);margin-bottom:6px}
.tag-card p{color:var(--muted);font-size:15px}
.projects-note{margin-top:28px;color:var(--muted);font-size:15px;font-style:italic}

/* ---- О компании ---- */
.about-inner{display:grid;grid-template-columns:1.4fr 1fr;gap:56px;align-items:start}
.about-text p{margin-bottom:16px;color:#3a4757;font-size:16px}
.about-list{list-style:none;background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:24px 26px;box-shadow:var(--shadow)}
.about-list li{padding:12px 0;border-bottom:1px solid var(--line);color:var(--muted)}
.about-list li:last-child{border-bottom:0}
.about-list b{color:var(--navy)}

/* ---- Контакты ---- */
.contacts-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:20px}
.contact-card{
  display:flex;flex-direction:column;gap:8px;
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);
  padding:26px 24px;transition:.2s;
}
.contact-card:not(.contact-card--static):hover{border-color:var(--accent);box-shadow:var(--shadow);transform:translateY(-3px)}
.contact-label{font-size:13px;text-transform:uppercase;letter-spacing:1px;color:var(--accent);font-weight:700}
.contact-value{font-size:17px;color:var(--navy);font-weight:600}

/* ---- Правовая страница ---- */
.legal{max-width:820px}
.legal p{color:#3a4757;font-size:16px;margin-bottom:14px;line-height:1.65}
.legal-h{font-size:19px;color:var(--navy);margin:26px 0 8px}
.legal a{color:var(--accent)}
.legal-back{margin-top:28px;font-weight:600}

/* ---- Контакты: раскладка + форма обратного звонка ---- */
.contacts-layout{display:grid;grid-template-columns:1fr 1fr;gap:24px;align-items:start}
.contacts-grid--2{grid-template-columns:1fr 1fr}
.callback{position:relative;overflow:hidden;background:#fff;border:1px solid var(--line);border-radius:16px;padding:32px 30px;box-shadow:0 14px 36px rgba(13,35,64,.10)}
.callback::before{content:"";position:absolute;top:0;left:0;right:0;height:4px;background:linear-gradient(90deg,var(--accent),#5aa0ec)}
.callback-title{font-size:22px;font-weight:800;color:var(--navy);margin-bottom:6px}
.callback-sub{color:var(--muted);font-size:14px;margin-bottom:20px}
#callbackForm{display:flex;flex-direction:column;gap:14px}
.callback-row{display:grid;grid-template-columns:1fr 1fr;gap:14px}
#callbackForm input[type=text],#callbackForm input[type=tel],#callbackForm textarea{
  width:100%;padding:13px 15px;border:1.5px solid var(--line);border-radius:10px;
  font:inherit;font-size:15px;color:var(--ink);background:var(--bg-alt);transition:.15s;
}
#callbackForm input::placeholder,#callbackForm textarea::placeholder{color:#9aa7b6}
#callbackForm input:focus,#callbackForm textarea:focus{outline:none;border-color:var(--accent);background:#fff;box-shadow:0 0 0 4px rgba(46,119,201,.12)}
#callbackForm textarea{resize:vertical;min-height:86px}
.hp{position:absolute!important;left:-9999px!important;width:1px;height:1px;opacity:0;pointer-events:none}
.callback-consent{display:flex;gap:10px;align-items:flex-start;font-size:13px;color:var(--muted);cursor:pointer;line-height:1.45}
.callback-consent input{margin-top:2px;flex:none;width:16px;height:16px;accent-color:var(--accent)}
.callback-consent a{color:var(--accent);text-decoration:underline}
.callback-btn{margin-top:6px;width:100%;padding:14px;font-size:16px}
.callback-msg{font-size:14px;margin:4px 0 0;line-height:1.45}
.callback-msg:empty{margin:0}
.callback-msg.is-success{color:#1a7f4b;font-weight:600}
.callback-msg.is-error{color:#c0392b;font-weight:600}
@media(max-width:820px){.contacts-layout{grid-template-columns:1fr}}
@media(max-width:520px){.contacts-grid--2{grid-template-columns:1fr}.callback-row{grid-template-columns:1fr}}

/* ---- Подвал ---- */
.site-footer{background:var(--navy);color:#c6d4e6;padding:48px 0 22px}
.footer-inner{display:grid;grid-template-columns:1.6fr 1fr 1fr;gap:32px;padding-bottom:30px;border-bottom:1px solid rgba(255,255,255,.1)}
.footer-brand p{margin-top:12px;font-size:14px;color:#9fb6d1}
.footer-req p{font-size:14px;margin-bottom:4px}
.footer-contacts{display:flex;flex-direction:column;gap:8px}
.footer-contacts a{font-size:15px;color:#e6eef7;font-weight:600}
.footer-contacts a:hover{color:#fff}
.footer-bottom{display:flex;justify-content:space-between;align-items:center;padding-top:18px;font-size:13px;color:#8298b3}
.to-top{color:#8298b3}
.to-top:hover{color:#fff}

/* ---- Адаптив ---- */
@media (max-width:900px){
  .grid-4{grid-template-columns:repeat(2,1fr)}
  .grid-3{grid-template-columns:repeat(2,1fr)}
  .about-inner{grid-template-columns:1fr;gap:32px}
  .contacts-grid{grid-template-columns:repeat(2,1fr)}
  .footer-inner{grid-template-columns:1fr 1fr}
}
@media (max-width:680px){
  .nav{
    position:absolute;top:72px;left:0;right:0;flex-direction:column;gap:0;
    background:var(--navy);padding:8px 24px 16px;
    border-bottom:1px solid rgba(255,255,255,.1);
    display:none;
  }
  .nav--open{display:flex}
  .nav a{padding:12px 0;border-bottom:1px solid rgba(255,255,255,.06)}
  .header-contacts{display:none}
  .burger{display:flex;margin-left:auto}
  .grid-4,.grid-3,.contacts-grid,.footer-inner{grid-template-columns:1fr}
  .hero-stats{gap:28px}
  .footer-bottom{flex-direction:column;gap:10px}
}