/* ============================================
   СЕЛЬЭНЕРГОМОНТАЖ — Design System
   Palette: Dark Navy + Cyan (from Hero image)
   ============================================ */

/* ---------- CSS Custom Properties ---------- */
:root {
  /* Colors */
  --color-bg-primary: #070e1b;
  --color-bg-secondary: #0d1a2d;
  --color-bg-card: rgba(13, 26, 45, 0.65);
  --color-bg-card-hover: rgba(13, 26, 45, 0.85);
  --color-accent: #00d4ff;
  --color-accent-dim: rgba(0, 212, 255, 0.15);
  --color-accent-glow: rgba(0, 212, 255, 0.35);
  --color-text-primary: #eaf0f9;
  --color-text-secondary: #8a9ab5;
  --color-text-heading: #ffffff;
  --color-border: rgba(255, 255, 255, 0.08);
  --color-success: #34d399;
  --color-error: #f87171;

  /* Typography */
  --font-body: 'Inter', system-ui, -apple-system, sans-serif;
  --font-heading: 'Outfit', var(--font-body);
  --fs-xs: clamp(0.75rem, 0.7rem + 0.25vw, 0.875rem);
  --fs-sm: clamp(0.875rem, 0.8rem + 0.35vw, 1rem);
  --fs-base: clamp(1rem, 0.9rem + 0.5vw, 1.125rem);
  --fs-lg: clamp(1.125rem, 1rem + 0.6vw, 1.35rem);
  --fs-xl: clamp(1.35rem, 1.1rem + 1.2vw, 1.75rem);
  --fs-2xl: clamp(1.75rem, 1.3rem + 2vw, 2.5rem);
  --fs-3xl: clamp(2.25rem, 1.5rem + 3.5vw, 3.75rem);

  /* Spacing */
  --space-xs: 0.5rem;
  --space-sm: 0.75rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2.5rem;
  --space-2xl: 4rem;
  --space-3xl: 6rem;

  /* Radii */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-card: 0 4px 30px rgba(0, 0, 0, 0.35);
  --shadow-glow: 0 0 25px var(--color-accent-glow);

  /* Transitions */
  --ease-out: cubic-bezier(0.25, 0.46, 0.45, 0.94);
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
  --duration-fast: 200ms;
  --duration-base: 350ms;
  --duration-slow: 600ms;

  /* Layout */
  --container-max: 1200px;
  --header-height: 72px;
}

/* ---------- Reset / Base ---------- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-body);
  font-size: var(--fs-base);
  line-height: 1.7;
  color: var(--color-text-primary);
  background-color: var(--color-bg-primary);
  overflow-x: hidden;
}

h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-heading);
  color: var(--color-text-heading);
  line-height: 1.2;
  font-weight: 600;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--duration-fast) var(--ease-out);
}

a:hover {
  color: #fff;
}

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

ul {
  list-style: none;
}

button,
input,
textarea {
  font-family: inherit;
  font-size: inherit;
  border: none;
  outline: none;
  background: none;
  color: inherit;
}

/* ---------- Utility ---------- */
.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.section {
  padding: var(--space-3xl) 0;
  position: relative;
}

.section-title {
  font-size: var(--fs-2xl);
  text-align: center;
  margin-bottom: var(--space-xl);
  position: relative;
}

.section-title::after {
  content: '';
  display: block;
  width: 60px;
  height: 3px;
  background: var(--color-accent);
  margin: var(--space-sm) auto 0;
  border-radius: var(--radius-full);
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ---------- Animations ---------- */
@keyframes fade-in-up {
  from {
    opacity: 0;
    transform: translateY(40px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fade-in {
  from {
    opacity: 0;
  }

  to {
    opacity: 1;
  }
}

@keyframes glow-pulse {

  0%,
  100% {
    box-shadow: 0 0 15px var(--color-accent-glow);
  }

  50% {
    box-shadow: 0 0 35px var(--color-accent-glow), 0 0 60px rgba(0, 212, 255, 0.15);
  }
}

.animate-on-scroll {
  opacity: 0;
  transform: translateY(40px);
  transition: opacity var(--duration-slow) var(--ease-out),
    transform var(--duration-slow) var(--ease-out);
}

.animate-on-scroll.is-visible {
  opacity: 1;
  transform: translateY(0);
}

/* stagger children */
.animate-on-scroll.is-visible .stagger-item:nth-child(1) {
  transition-delay: 0ms;
}

.animate-on-scroll.is-visible .stagger-item:nth-child(2) {
  transition-delay: 100ms;
}

.animate-on-scroll.is-visible .stagger-item:nth-child(3) {
  transition-delay: 200ms;
}

.animate-on-scroll.is-visible .stagger-item:nth-child(4) {
  transition-delay: 300ms;
}

.animate-on-scroll.is-visible .stagger-item:nth-child(5) {
  transition-delay: 400ms;
}

.animate-on-scroll.is-visible .stagger-item:nth-child(6) {
  transition-delay: 500ms;
}

.stagger-item {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity var(--duration-slow) var(--ease-out),
    transform var(--duration-slow) var(--ease-out);
}

.animate-on-scroll.is-visible .stagger-item {
  opacity: 1;
  transform: translateY(0);
}

/* ============================================
   HEADER
   ============================================ */
.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: var(--header-height);
  z-index: 1000;
  transition: background var(--duration-base) var(--ease-out),
    box-shadow var(--duration-base) var(--ease-out);
}

.header.scrolled {
  background: rgba(7, 14, 27, 0.92);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  box-shadow: 0 2px 24px rgba(0, 0, 0, 0.4);
}

.header__inner {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-lg);
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.header__logo {
  font-family: var(--font-heading);
  font-size: var(--fs-xl);
  font-weight: 700;
  color: var(--color-text-heading);
  letter-spacing: -0.025em;
}

.header__logo span {
  color: var(--color-accent);
}

.header__nav {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
}

.header__nav a {
  color: var(--color-text-secondary);
  font-size: var(--fs-sm);
  font-weight: 500;
  transition: color var(--duration-fast) var(--ease-out);
}

.header__nav a:hover {
  color: var(--color-accent);
}

.header__cta {
  display: inline-flex;
}

.header__cta-icon {
  display: none;
  width: 18px;
  height: 18px;
}

/* Burger */
.burger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  z-index: 1100;
  background: none;
  border: none;
  padding: 4px;
}

.burger span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text-primary);
  border-radius: 2px;
  transition: transform var(--duration-base) var(--ease-out),
    opacity var(--duration-base) var(--ease-out);
}

.burger.open span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.burger.open span:nth-child(2) {
  opacity: 0;
}

.burger.open span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ============================================
   HERO
   ============================================ */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.hero__bg {
  position: absolute;
  inset: 0;
  z-index: 0;
}

.hero__bg img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  will-change: transform;
}

.hero__overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg,
      rgba(7, 14, 27, 0.15) 0%,
      rgba(7, 14, 27, 0.35) 50%,
      rgba(7, 14, 27, 0.85) 100%);
  z-index: 1;
}

.hero__content {
  position: relative;
  z-index: 2;
  text-align: center;
  max-width: 800px;
  padding: var(--space-2xl) var(--space-lg);
  animation: fade-in-up 1s var(--ease-out) 0.3s both;
}

.hero__title {
  font-size: var(--fs-3xl);
  font-weight: 700;
  margin-bottom: var(--space-md);
  letter-spacing: -0.03em;
}

.hero__title span {
  color: var(--color-accent);
}

.hero__subtitle {
  font-size: var(--fs-lg);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-xl);
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

/* ============================================
   BUTTONS
   ============================================ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  padding: 14px 32px;
  border-radius: var(--radius-full);
  font-weight: 600;
  font-size: var(--fs-sm);
  cursor: pointer;
  transition: all var(--duration-base) var(--ease-out);
  white-space: nowrap;
}

.btn--primary {
  background: var(--color-accent);
  color: var(--color-bg-primary);
  box-shadow: 0 0 20px var(--color-accent-glow);
}

.btn--primary:hover {
  background: #33ddff;
  color: var(--color-bg-primary);
  box-shadow: 0 0 35px var(--color-accent-glow), 0 4px 20px rgba(0, 0, 0, 0.3);
  transform: translateY(-2px);
}

.btn--outline {
  border: 1.5px solid var(--color-accent);
  color: var(--color-accent);
  background: transparent;
}

.btn--outline:hover {
  background: var(--color-accent-dim);
  color: #fff;
  transform: translateY(-2px);
}

.btn--sm {
  padding: 10px 24px;
  font-size: var(--fs-xs);
}

/* ============================================
   SERVICES
   ============================================ */
.services__grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-lg);
}

.service-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: all var(--duration-base) var(--ease-out);
  text-align: center;
}

.service-card:hover {
  background: var(--color-bg-card-hover);
  border-color: rgba(0, 212, 255, 0.25);
  transform: translateY(-6px);
  box-shadow: var(--shadow-card), 0 0 30px rgba(0, 212, 255, 0.08);
}

.service-card__icon {
  width: 56px;
  height: 56px;
  margin: 0 auto var(--space-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  background: var(--color-accent-dim);
  color: var(--color-accent);
}

.service-card__icon svg {
  width: 28px;
  height: 28px;
}

.service-card__title {
  font-size: var(--fs-xl);
  margin-bottom: var(--space-sm);
}

.service-card__desc {
  color: var(--color-text-secondary);
  font-size: var(--fs-sm);
  line-height: 1.6;
}

/* ============================================
   CASES (Masonry)
   ============================================ */
.cases {
  background: var(--color-bg-secondary);
}

.cases__grid {
  column-count: 3;
  column-gap: var(--space-md);
}

.case-item {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  break-inside: avoid;
  margin-bottom: var(--space-md);
  transition: all var(--duration-base) var(--ease-out);
}

.case-item:hover {
  border-color: rgba(0, 212, 255, 0.2);
  transform: translateY(-4px);
  box-shadow: var(--shadow-card), 0 0 20px rgba(0, 212, 255, 0.05);
}

.case-item__num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  background: var(--color-accent-dim);
  color: var(--color-accent);
  border-radius: var(--radius-sm);
  font-weight: 700;
  font-size: var(--fs-xs);
  margin-bottom: var(--space-sm);
}

.case-item__title {
  font-family: var(--font-heading);
  font-size: var(--fs-xl);
  font-weight: 600;
  color: var(--color-text-heading);
  line-height: 1.3;
  margin-bottom: var(--space-sm);
  letter-spacing: -0.01em;
}

.case-item__desc {
  color: var(--color-text-secondary);
  font-size: var(--fs-sm);
  line-height: 1.6;
}

/* ============================================
   ADVANTAGES
   ============================================ */
.advantages__grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-lg);
}

.adv-card {
  text-align: center;
  padding: var(--space-xl);
  border-radius: var(--radius-lg);
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: all var(--duration-base) var(--ease-out);
}

.adv-card:hover {
  transform: translateY(-4px);
  border-color: rgba(0, 212, 255, 0.2);
  box-shadow: var(--shadow-card);
}

.adv-card__icon {
  width: 52px;
  height: 52px;
  margin: 0 auto var(--space-md);
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: var(--color-accent-dim);
  color: var(--color-accent);
}

.adv-card__icon svg {
  width: 24px;
  height: 24px;
}

.adv-card__title {
  font-size: var(--fs-lg);
  margin-bottom: var(--space-xs);
}

.adv-card__desc {
  color: var(--color-text-secondary);
  font-size: var(--fs-sm);
}

/* ============================================
   CONTACT / FORM
   ============================================ */
.contact {
  background: var(--color-bg-secondary);
}

.contact__wrapper {
  max-width: 560px;
  margin: 0 auto;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-2xl);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: var(--shadow-card);
}

.contact__subtitle {
  text-align: center;
  color: var(--color-text-secondary);
  font-size: var(--fs-sm);
  margin-bottom: var(--space-xl);
}

.form__group {
  margin-bottom: var(--space-lg);
}

.form__label {
  display: block;
  font-size: var(--fs-sm);
  font-weight: 500;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-xs);
}

.form__input {
  width: 100%;
  padding: 14px 18px;
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  color: var(--color-text-primary);
  font-size: var(--fs-base);
  transition: border-color var(--duration-fast) var(--ease-out),
    box-shadow var(--duration-fast) var(--ease-out);
}

.form__input::placeholder {
  color: rgba(138, 154, 181, 0.5);
}

.form__input:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px var(--color-accent-dim);
}

.form__input.error {
  border-color: var(--color-error);
  box-shadow: 0 0 0 3px rgba(248, 113, 113, 0.15);
}

.form__error {
  color: var(--color-error);
  font-size: var(--fs-xs);
  margin-top: var(--space-xs);
  display: none;
}

.form__error.visible {
  display: block;
}

.form__submit {
  width: 100%;
  margin-top: var(--space-sm);
}

.form__success {
  display: none;
  text-align: center;
  padding: var(--space-xl);
}

.form__success.visible {
  display: block;
}

.form__success__icon {
  width: 56px;
  height: 56px;
  margin: 0 auto var(--space-md);
  border-radius: 50%;
  background: rgba(52, 211, 153, 0.15);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-success);
}

.form__success__title {
  font-size: var(--fs-xl);
  margin-bottom: var(--space-xs);
}

.form__success__desc {
  color: var(--color-text-secondary);
  font-size: var(--fs-sm);
}

/* ============================================
   FOOTER
   ============================================ */
.footer {
  padding: var(--space-xl) 0;
  border-top: 1px solid var(--color-border);
}

.footer__container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-md);
  text-align: center;
}

@media (min-width: 768px) {
  .footer__container {
    flex-direction: row;
    justify-content: space-between;
    text-align: left;
  }
}

.footer__legal,
.footer__copy {
  color: var(--color-text-secondary);
  font-size: var(--fs-xs);
  line-height: 1.5;
}

.footer__legal p {
  margin-bottom: 0.25rem;
}

.footer__legal p:last-child {
  margin-bottom: 0;
}

/* ============================================
   RESPONSIVE
   ============================================ */
@media (max-width: 1024px) {

  .services__grid,
  .advantages__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .cases__grid {
    column-count: 2;
  }
}

@media (max-width: 768px) {
  .header__nav {
    position: fixed;
    top: 0;
    right: 0;
    width: 280px;
    height: 100vh;
    background: rgba(7, 14, 27, 0.97);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    flex-direction: column;
    justify-content: center;
    gap: var(--space-xl);
    transform: translateX(100%);
    transition: transform var(--duration-base) var(--ease-out);
    z-index: 1050;
  }

  .header__nav.open {
    transform: translateX(0);
  }

  .header__nav a {
    font-size: var(--fs-lg);
  }

  .burger {
    display: flex;
  }

  .header__cta {
    margin-left: auto;
    margin-right: var(--space-md);
    padding: 10px;
    border-radius: 50%;
    width: 44px;
    height: 44px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
  }

  .header__cta-text {
    display: none;
  }

  .header__cta-icon {
    display: block;
    width: 20px;
    height: 20px;
  }

  .services__grid,
  .advantages__grid {
    grid-template-columns: 1fr;
  }

  .cases__grid {
    column-count: 1;
  }

  .contact__wrapper {
    padding: var(--space-xl);
  }

  .hero__title {
    font-size: clamp(1.8rem, 1.2rem + 3vw, 2.8rem);
  }
}