/* ============================================================
   VoltNova Energy — global styles
   Plain CSS, no build step. RTL-safe via logical properties.
   ============================================================ */

:root {
  --brand: #0b1f3a;
  --brand-2: #0e2a4d;
  --accent: #1fd1a8;
  --accent-ink: #064e3f;
  --bg: #ffffff;
  --bg-alt: #f4f7fb;
  --ink: #0b1f3a;
  --ink-soft: #51627c;
  --line: #e3e9f2;
  --white: #ffffff;
  --danger: #d64545;
  --radius: 14px;
  --radius-sm: 10px;
  --shadow-sm: 0 1px 3px rgba(11, 31, 58, 0.08);
  --shadow-md: 0 10px 30px rgba(11, 31, 58, 0.10);
  --shadow-lg: 0 24px 60px rgba(11, 31, 58, 0.18);
  --container: 1140px;
  --space: clamp(3.5rem, 7vw, 6.5rem);
  --font-sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue",
    "PingFang SC", "Microsoft YaHei", Arial, sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font-sans);
  color: var(--ink);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

img, svg { max-width: 100%; display: block; }

a { color: var(--accent-ink); text-decoration: none; }
a:hover { text-decoration: underline; }

h1, h2, h3 { line-height: 1.15; color: var(--ink); margin: 0 0 0.5em; }
h1 { font-size: clamp(2rem, 5vw, 3.4rem); letter-spacing: -0.02em; }
h2 { font-size: clamp(1.6rem, 3.4vw, 2.4rem); letter-spacing: -0.01em; }
h3 { font-size: 1.15rem; }
p { margin: 0 0 1em; }

.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: clamp(1rem, 4vw, 2rem);
}

/* ---------- Accessibility helpers ---------- */
.visually-hidden,
.skip-link {
  position: absolute;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}
.skip-link:focus {
  position: fixed;
  inset-block-start: 0.75rem;
  inset-inline-start: 0.75rem;
  width: auto; height: auto;
  clip: auto;
  background: var(--brand);
  color: #fff;
  padding: 0.6rem 1rem;
  border-radius: var(--radius-sm);
  z-index: 1000;
}

:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 2px;
  border-radius: 4px;
}

/* ---------- Header / Nav ---------- */
.site-header {
  position: sticky;
  inset-block-start: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: saturate(140%) blur(10px);
  border-bottom: 1px solid transparent;
  transition: box-shadow 0.25s, border-color 0.25s;
}
.site-header.scrolled {
  box-shadow: var(--shadow-sm);
  border-bottom-color: var(--line);
}
.nav {
  display: flex;
  align-items: center;
  gap: 1rem;
  min-height: 68px;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 800;
  color: var(--brand);
  font-size: 1.15rem;
}
.brand:hover { text-decoration: none; }
.brand__mark { color: var(--accent); flex: none; }
.brand__accent { color: var(--accent); }

.primary-nav { margin-inline-start: auto; }
.nav-list {
  list-style: none;
  display: flex;
  align-items: center;
  gap: 0.35rem;
  margin: 0; padding: 0;
}
.nav-list a {
  display: inline-block;
  padding: 0.5rem 0.85rem;
  border-radius: 999px;
  color: var(--ink);
  font-weight: 600;
  font-size: 0.95rem;
}
.nav-list a:hover { background: var(--bg-alt); text-decoration: none; }
.nav-cta {
  background: var(--accent);
  color: var(--accent-ink) !important;
  padding: 0.55rem 1.1rem !important;
}
.nav-cta:hover { background: #19b995; }

.lang-switch { margin-inline-start: 0.5rem; }
.lang-select {
  appearance: none;
  border: 1px solid var(--line);
  background: var(--white);
  color: var(--ink);
  padding: 0.45rem 2rem 0.45rem 0.75rem;
  border-radius: 999px;
  font: inherit;
  font-size: 0.9rem;
  cursor: pointer;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%2351627c' stroke-width='3'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.7rem center;
}

.nav-toggle {
  display: none;
  margin-inline-start: auto;
  flex-direction: column;
  gap: 5px;
  width: 44px; height: 44px;
  border: 1px solid var(--line);
  background: #fff;
  border-radius: 10px;
  cursor: pointer;
  padding: 0;
  align-items: center;
  justify-content: center;
}
.nav-toggle span {
  width: 20px; height: 2px;
  background: var(--brand);
  border-radius: 2px;
  transition: transform 0.25s, opacity 0.25s;
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.8rem 1.4rem;
  border-radius: 999px;
  font-weight: 700;
  font-size: 1rem;
  cursor: pointer;
  border: 1px solid transparent;
  transition: transform 0.15s, background 0.2s, box-shadow 0.2s;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn--primary { background: var(--accent); color: var(--accent-ink); box-shadow: var(--shadow-sm); }
.btn--primary:hover { background: #19b995; }
.btn--ghost { background: transparent; color: #fff; border-color: rgba(255, 255, 255, 0.5); }
.btn--ghost:hover { background: rgba(255, 255, 255, 0.12); }
.btn--block { width: 100%; }

/* ---------- Hero ---------- */
.hero {
  position: relative;
  background: radial-gradient(120% 120% at 80% 0%, #123a63 0%, var(--brand) 55%);
  color: #fff;
  overflow: hidden;
}
.hero__bg { position: absolute; inset: 0; z-index: 0; }
.hero__inner {
  position: relative;
  z-index: 1;
  padding-block: clamp(4rem, 12vh, 8rem);
  max-width: 880px;
}
.hero__badge {
  display: inline-block;
  background: rgba(31, 209, 168, 0.15);
  color: var(--accent);
  border: 1px solid rgba(31, 209, 168, 0.35);
  padding: 0.4rem 0.9rem;
  border-radius: 999px;
  font-size: 0.85rem;
  font-weight: 700;
  margin-bottom: 1.2rem;
}
.hero__title { color: #fff; }
.hero__subtitle {
  font-size: 1.15rem;
  color: rgba(255, 255, 255, 0.85);
  max-width: 620px;
}
.hero__actions { display: flex; flex-wrap: wrap; gap: 0.8rem; margin-block: 1.8rem 2.5rem; }
.hero__stats {
  display: flex;
  flex-wrap: wrap;
  gap: 2.5rem;
}
.hero__stats .stat-num { font-size: 2rem; font-weight: 800; color: #fff; }
.hero__stats .stat-label { font-size: 0.9rem; color: rgba(255, 255, 255, 0.75); }

/* ---------- Sections ---------- */
.section { padding-block: var(--space); }
.section--alt { background: var(--bg-alt); }
.eyebrow {
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--accent-ink);
  margin: 0 0 0.5rem;
}
.section-title { margin-bottom: 0.6rem; }
.section-lead {
  max-width: 640px;
  color: var(--ink-soft);
  font-size: 1.05rem;
  margin-bottom: 2.5rem;
}

/* ---------- Product grid ---------- */
.product-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.4rem;
}
.card {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.6rem;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s, box-shadow 0.2s, border-color 0.2s;
  display: flex;
  flex-direction: column;
}
.card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); border-color: #cfe9e1; }
.card__icon {
  width: 52px; height: 52px;
  display: grid; place-items: center;
  border-radius: 12px;
  background: rgba(31, 209, 168, 0.12);
  color: var(--accent-ink);
  margin-bottom: 1rem;
}
.card__img {
  width: 100%;
  height: 170px;
  object-fit: cover;
  border-radius: 10px;
  margin-bottom: 1rem;
  background: var(--bg-alt);
}
.card__title { font-size: 1.2rem; margin-bottom: 0.4rem; }
.card__desc { color: var(--ink-soft); font-size: 0.95rem; flex: 1; }
.card__features {
  list-style: none;
  margin: 1rem 0 0;
  padding: 0;
  display: grid;
  gap: 0.4rem;
}
.card__features li {
  font-size: 0.88rem;
  color: var(--ink);
  padding-inline-start: 1.4rem;
  position: relative;
}
.card__features li::before {
  content: "✓";
  position: absolute;
  inset-inline-start: 0;
  color: var(--accent-ink);
  font-weight: 800;
}

/* ---------- Solutions flow ---------- */
.flow {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
  margin-bottom: 2rem;
}
.flow-step {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.4rem;
  position: relative;
}
.flow-step__icon {
  width: 46px; height: 46px;
  border-radius: 12px;
  background: var(--brand);
  color: var(--accent);
  display: grid; place-items: center;
  margin-bottom: 0.8rem;
}
.flow-step__title { font-weight: 700; margin-bottom: 0.3rem; }
.flow-step__desc { font-size: 0.92rem; color: var(--ink-soft); }
.flow-step__num {
  position: absolute;
  inset-block-start: 1rem;
  inset-inline-end: 1.2rem;
  font-size: 0.85rem;
  font-weight: 800;
  color: var(--accent);
}
.benefit-list {
  list-style: none;
  margin: 0; padding: 0;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 0.8rem;
}
.benefit-list li {
  background: var(--brand);
  color: #fff;
  padding: 0.9rem 1.1rem;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 600;
}

/* ---------- Advantages ---------- */
.advantage-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.2rem;
}
.advantage {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
}
.advantage__icon { color: var(--accent-ink); margin-bottom: 0.6rem; }
.advantage__title { font-size: 1.1rem; margin-bottom: 0.3rem; }
.advantage__desc { color: var(--ink-soft); font-size: 0.95rem; margin: 0; }

/* ---------- About ---------- */
.about {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 2.5rem;
  align-items: center;
}
.about__body { color: var(--ink-soft); }
.about__visual {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
}

/* ---------- Certifications ---------- */
.cert-list {
  list-style: none;
  margin: 0; padding: 0;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 1rem;
}
.cert {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.2rem;
  text-align: center;
  background: #fff;
}
.cert__name { font-weight: 800; font-size: 1.2rem; color: var(--brand); }
.cert__desc { font-size: 0.85rem; color: var(--ink-soft); margin: 0; }

/* ---------- Contact / form ---------- */
.contact {
  display: grid;
  grid-template-columns: 0.85fr 1.15fr;
  gap: 2.5rem;
  align-items: start;
}
.contact__lines { list-style: none; margin: 1.5rem 0 0; padding: 0; display: grid; gap: 1rem; }
.contact__lines li { font-size: 0.95rem; }
.contact__lines strong { color: var(--brand); }

.inquiry {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.6rem;
  box-shadow: var(--shadow-sm);
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}
.field { display: flex; flex-direction: column; gap: 0.35rem; }
.field--full { grid-column: 1 / -1; }
.field label { font-size: 0.9rem; font-weight: 600; color: var(--ink); }
.field input,
.field select,
.field textarea {
  font: inherit;
  padding: 0.7rem 0.85rem;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: #fff;
  color: var(--ink);
  width: 100%;
}
.field input:focus,
.field select:focus,
.field textarea:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(31, 209, 168, 0.25);
}
.field input[aria-invalid="true"],
.field textarea[aria-invalid="true"] {
  border-color: var(--danger);
}
.form-status {
  grid-column: 1 / -1;
  margin: 0;
  font-weight: 600;
  min-height: 1.2em;
}
.form-status.ok { color: var(--accent-ink); }
.form-status.err { color: var(--danger); }

/* ---------- Footer ---------- */
.site-footer {
  background: var(--brand);
  color: rgba(255, 255, 255, 0.8);
  padding-block: 3rem 1.5rem;
}
.footer-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  gap: 2rem;
}
.footer-col h3 { color: #fff; font-size: 1rem; margin-bottom: 0.8rem; }
.footer-col ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.5rem; }
.footer-col a { color: rgba(255, 255, 255, 0.8); }
.footer-col a:hover { color: #fff; }
.footer-brand .brand__name { color: #fff; font-size: 1.2rem; font-weight: 800; }
.footer-brand p { margin-top: 0.6rem; font-size: 0.92rem; }
.footer-bottom {
  margin-top: 2rem;
  padding-top: 1.2rem;
  border-top: 1px solid rgba(255, 255, 255, 0.12);
  font-size: 0.88rem;
  color: rgba(255, 255, 255, 0.6);
}

/* ---------- Reveal animation ---------- */
.reveal { opacity: 0; transform: translateY(18px); transition: opacity 0.6s ease, transform 0.6s ease; }
.reveal.in { opacity: 1; transform: none; }

/* ---------- Responsive ---------- */
@media (max-width: 920px) {
  .about { grid-template-columns: 1fr; }
  .contact { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 820px) {
  .nav-toggle { display: flex; }
  .lang-switch { margin-inline-start: 0; }
  .primary-nav {
    position: absolute;
    inset-block-start: 68px;
    inset-inline: 0;
    background: #fff;
    border-bottom: 1px solid var(--line);
    box-shadow: var(--shadow-md);
    margin: 0;
    display: none;
  }
  .primary-nav.open { display: block; }
  .nav-list { flex-direction: column; align-items: stretch; gap: 0; padding: 0.5rem; }
  .nav-list li { width: 100%; }
  .nav-list a { display: block; padding: 0.85rem 1rem; }
  .nav-cta { text-align: center; margin: 0.4rem; }
}
@media (max-width: 620px) {
  .inquiry { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
  .hero__stats { gap: 1.5rem; }
}

/* ---------- Reduced motion ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { transition: none !important; animation: none !important; }
  .reveal { opacity: 1; transform: none; }
}