/* ==========================================================================
   ENTA2C BTP — FLAGSHIP INSTITUTIONAL DESIGN SYSTEM
   Senior UX Director & Design System Architect Specification
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=DM+Mono:ital,wght@0,400;0,500;1,400&family=Inter:wght@300;400;500;600;700&family=Syne:wght@500;600;700;800&display=swap');

:root {
  /* Chromatic Tokens */
  --color-navy-deep: #0B1F3A;
  --color-navy-slate: #162C4E;
  --color-navy-dark: #071426;
  --color-concrete: #8A9099;
  --color-surface: #F8F9FA;
  --color-white: #FFFFFF;
  --color-gold: #C9A84C;
  --color-gold-hover: #D8B75B;
  --color-border: rgba(138, 144, 153, 0.2);
  --color-border-dark: rgba(255, 255, 255, 0.08);

  /* Typography Tokens */
  --font-heading: 'Syne', sans-serif;
  --font-body: 'Inter', sans-serif;
  --font-mono: 'DM Mono', monospace;

  /* Spacing System (8px Grid) */
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --space-10: 80px;
  --space-15: 120px;

  /* Elevation & Shadows */
  --shadow-subtle: 0 10px 30px rgba(11, 31, 58, 0.06);
  --shadow-card: 0 20px 40px rgba(7, 20, 38, 0.12);
  --shadow-gold: 0 8px 24px rgba(201, 168, 76, 0.25);

  /* Transitions */
  --transition-smooth: all 0.4s cubic-bezier(0.16, 1, 0.3, 1);
  --transition-fast: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
  background-color: var(--color-navy-deep);
  color: var(--color-surface);
}

body {
  font-family: var(--font-body);
  font-size: clamp(1rem, 0.5vw + 0.875rem, 1.125rem); /* 16px - 18px strictly */
  line-height: 1.6;
  color: var(--color-surface);
  background-color: var(--color-navy-deep);
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* Typography Rules */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.02em;
  color: var(--color-white);
}

h1 {
  font-size: clamp(2.125rem, 3.5vw + 1rem, 3.5rem); /* 34px - 56px max */
}

h2 {
  font-size: clamp(1.75rem, 2.5vw + 0.5rem, 2.5rem); /* 28px - 40px max */
}

h3 {
  font-size: clamp(1.375rem, 1.5vw + 0.5rem, 1.75rem); /* 22px - 28px max */
}

h4 {
  font-size: clamp(1.125rem, 1vw + 0.5rem, 1.25rem); /* 18px - 20px max */
}

p {
  max-width: 720px;
  color: var(--color-concrete);
  line-height: 1.65;
}

p.lead {
  font-size: clamp(1.125rem, 0.5vw + 1rem, 1.25rem);
  color: var(--color-surface);
  font-weight: 400;
}

.mono-tag {
  font-family: var(--font-mono);
  font-size: 0.875rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--color-gold);
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
}

.mono-tag::before {
  content: "";
  display: inline-block;
  width: 16px;
  height: 2px;
  background-color: var(--color-gold);
}

/* Structural Container & Grids */
.container {
  width: 100%;
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 var(--space-3);
}

@media (min-width: 1024px) {
  .container {
    padding: 0 var(--space-6);
  }
}

.grid-12 {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: var(--space-3);
}

@media (min-width: 768px) {
  .grid-12 {
    gap: var(--space-4);
  }
}

/* Sections */
section {
  padding: var(--space-8) 0;
  position: relative;
}

@media (min-width: 1024px) {
  section {
    padding: var(--space-15) 0;
  }
}

.section-dark {
  background-color: var(--color-navy-dark);
}

.section-slate {
  background-color: var(--color-navy-slate);
}

.section-light {
  background-color: var(--color-surface);
  color: var(--color-navy-deep);
}

.section-light h1, .section-light h2, .section-light h3, .section-light h4 {
  color: var(--color-navy-deep);
}

.section-light p {
  color: #4B5563;
}

/* Header & Navigation */
header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 1000;
  background: rgba(11, 31, 58, 0.88);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border-dark);
  transition: var(--transition-smooth);
}

header.scrolled {
  background: rgba(7, 20, 38, 0.96);
  padding: 4px 0;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

.nav-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 80px;
}

.logo {
  font-family: var(--font-body);
  font-size: 1.45rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  color: var(--color-white);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 1px;
  transition: var(--transition-fast);
}

.logo span {
  color: var(--color-gold);
  font-weight: 500;
  letter-spacing: 0.02em;
  transition: var(--transition-fast);
}

.logo:hover {
  opacity: 0.9;
  transform: translateY(-1px);
}

.nav-links {
  display: none;
  list-style: none;
  gap: var(--space-4);
  align-items: center;
}

@media (min-width: 1024px) {
  .nav-links {
    display: flex;
  }
}

.nav-links a {
  font-family: var(--font-body);
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--color-surface);
  text-decoration: none;
  transition: var(--transition-fast);
  position: relative;
  padding: var(--space-1) 0;
}

.nav-links a::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--color-gold);
  transition: var(--transition-fast);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--color-gold);
}

.nav-links a:hover::after,
.nav-links a.active::after {
  width: 100%;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  padding: 14px 28px;
  font-family: var(--font-body);
  font-size: 0.9375rem;
  font-weight: 600;
  text-decoration: none;
  border-radius: 2px;
  cursor: pointer;
  transition: var(--transition-fast);
  min-height: 48px; /* Touch target >= 44px */
}

.btn-gold {
  background-color: var(--color-gold);
  color: var(--color-navy-deep);
  border: 1px solid var(--color-gold);
}

.btn-gold:hover {
  background-color: var(--color-gold-hover);
  border-color: var(--color-gold-hover);
  transform: translateY(-2px);
  box-shadow: var(--shadow-gold);
}

.btn-outline {
  background-color: transparent;
  color: var(--color-white);
  border: 1px solid var(--color-border-dark);
}

.btn-outline:hover {
  border-color: var(--color-gold);
  color: var(--color-gold);
}

/* Mobile Menu Button */
.menu-toggle {
  display: block;
  background: transparent;
  border: none;
  color: var(--color-white);
  font-size: 1.5rem;
  cursor: pointer;
  padding: var(--space-1);
}

@media (min-width: 1024px) {
  .menu-toggle {
    display: none;
  }
}

/* Mobile Drawer */
.mobile-drawer {
  position: fixed;
  top: 0;
  right: -100%;
  width: 100%;
  max-width: 400px;
  height: 100vh;
  background: var(--color-navy-dark);
  z-index: 2000;
  padding: var(--space-6) var(--space-4);
  transition: right 0.4s cubic-bezier(0.16, 1, 0.3, 1);
  box-shadow: -10px 0 30px rgba(0, 0, 0, 0.5);
  display: flex;
  flex-direction: column;
}

.mobile-drawer.open {
  right: 0;
}

.drawer-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-6);
}

.drawer-close {
  background: transparent;
  border: none;
  color: var(--color-white);
  font-size: 1.75rem;
  cursor: pointer;
}

.drawer-nav {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.drawer-nav a {
  font-family: var(--font-heading);
  font-size: 1.5rem;
  color: var(--color-white);
  text-decoration: none;
  transition: var(--transition-fast);
}

.drawer-nav a:hover, .drawer-nav a.active {
  color: var(--color-gold);
}

/* Image System */
.img-aspect-16-9 {
  aspect-ratio: 16 / 9;
  width: 100%;
  object-fit: cover;
  background-color: var(--color-navy-slate);
}

.img-aspect-4-5 {
  aspect-ratio: 4 / 5;
  width: 100%;
  object-fit: cover;
  background-color: var(--color-navy-slate);
}

/* Card System */
.card-engineering {
  background-color: var(--color-navy-slate);
  border: 1px solid var(--color-border-dark);
  padding: var(--space-4);
  transition: var(--transition-smooth);
  height: 100%;
  display: flex;
  flex-direction: column;
}

.card-engineering:hover {
  border-color: var(--color-gold);
  transform: translateY(-4px);
  box-shadow: var(--shadow-card);
}

/* Floating WhatsApp / Mobile Contact Button */
.sticky-contact {
  position: fixed;
  bottom: 24px;
  right: 24px;
  z-index: 990;
  display: flex;
  align-items: center;
  gap: var(--space-1);
  background-color: #25D366;
  color: #FFFFFF;
  padding: 12px 20px;
  border-radius: 50px;
  font-weight: 600;
  text-decoration: none;
  box-shadow: 0 8px 24px rgba(37, 211, 102, 0.4);
  transition: var(--transition-fast);
}

.sticky-contact:hover {
  transform: scale(1.05);
  box-shadow: 0 12px 30px rgba(37, 211, 102, 0.6);
}

/* Footer */
footer {
  background-color: var(--color-navy-dark);
  border-top: 1px solid var(--color-border-dark);
  padding: var(--space-10) 0 var(--space-6);
  color: var(--color-concrete);
}

.footer-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-6);
  margin-bottom: var(--space-8);
}

@media (min-width: 768px) {
  .footer-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .footer-grid {
    grid-template-columns: 2fr 1fr 1fr 1.5fr;
  }
}

.footer-col h4 {
  color: var(--color-white);
  margin-bottom: var(--space-3);
  font-size: 1.125rem;
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.footer-links a {
  color: var(--color-concrete);
  text-decoration: none;
  transition: var(--transition-fast);
}

.footer-links a:hover {
  color: var(--color-gold);
}

.footer-bottom {
  border-top: 1px solid var(--color-border-dark);
  padding-top: var(--space-4);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  justify-content: space-between;
  align-items: center;
  font-size: 0.875rem;
}

@media (min-width: 768px) {
  .footer-bottom {
    flex-direction: row;
  }
}

/* Scroll Animations */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.7s cubic-bezier(0.16, 1, 0.3, 1), transform 0.7s cubic-bezier(0.16, 1, 0.3, 1);
}

.reveal.active {
  opacity: 1;
  transform: translateY(0);
}