/* ============================================
   TECH STACX — Global Stylesheet
   Grayscale / Dark / Professional
   ============================================ */

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

:root {
  --black: #0a0a0a;
  --dark: #111111;
  --dark-mid: #1a1a1a;
  --mid: #2a2a2a;
  --gray: #888888;
  --light-gray: #b0b0b0;
  --off-white: #e8e8e8;
  --white: #f5f5f5;
  --pure-white: #ffffff;
  --accent: #c0c0c0;
  --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-display: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --max-width: 1200px;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-primary);
  background-color: var(--black);
  color: var(--off-white);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: var(--white);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--light-gray);
}

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

/* --- Typography --- */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 300;
  letter-spacing: -0.02em;
  line-height: 1.2;
  color: var(--white);
}

h1 {
  font-size: clamp(2.5rem, 5vw, 4.5rem);
  letter-spacing: -0.03em;
}

h2 {
  font-size: clamp(1.8rem, 3.5vw, 3rem);
  margin-bottom: 1.5rem;
}

h3 {
  font-size: clamp(1.2rem, 2vw, 1.6rem);
  font-weight: 400;
  margin-bottom: 1rem;
}

p {
  font-size: 1.05rem;
  color: var(--light-gray);
  max-width: 680px;
}

.label {
  font-size: 0.75rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--gray);
  font-weight: 500;
  margin-bottom: 1rem;
  display: block;
}

/* --- Navigation --- */
nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  padding: 1.5rem 3rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: rgba(10, 10, 10, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
  transition: all var(--transition);
}

.nav-logo {
  font-size: 1.1rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--white);
}

.nav-logo span {
  font-weight: 300;
  color: var(--gray);
}

.nav-links {
  display: flex;
  gap: 2.5rem;
  list-style: none;
  align-items: center;
}

.nav-links a {
  font-size: 0.8rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--gray);
  transition: color var(--transition);
  position: relative;
}

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

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 1px;
  background: var(--white);
  transition: width var(--transition);
}

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

/* Mobile nav */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.5rem;
}

.nav-toggle span {
  display: block;
  width: 24px;
  height: 1px;
  background: var(--white);
  margin: 6px 0;
  transition: all var(--transition);
}

/* --- Layout --- */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 3rem;
}

section {
  padding: 8rem 0;
}

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

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

/* --- Hero --- */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  position: relative;
  padding-top: 6rem;
}

.hero-content {
  max-width: 800px;
}

.hero h1 {
  margin-bottom: 1.5rem;
}

.hero p {
  font-size: 1.2rem;
  margin-bottom: 2.5rem;
  max-width: 600px;
}

.hero-line {
  width: 60px;
  height: 1px;
  background: var(--gray);
  margin-bottom: 2rem;
}

/* --- Buttons --- */
.btn {
  display: inline-block;
  padding: 0.9rem 2.2rem;
  font-size: 0.8rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  font-weight: 500;
  border: 1px solid var(--gray);
  color: var(--white);
  background: transparent;
  cursor: pointer;
  transition: all var(--transition);
  font-family: var(--font-primary);
}

.btn:hover {
  background: var(--white);
  color: var(--black);
  border-color: var(--white);
}

.btn-filled {
  background: var(--white);
  color: var(--black);
  border-color: var(--white);
}

.btn-filled:hover {
  background: transparent;
  color: var(--white);
}

/* --- Grid layouts --- */
.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
  align-items: start;
}

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

/* --- Cards --- */
.card {
  padding: 2.5rem;
  border: 1px solid rgba(255, 255, 255, 0.06);
  background: var(--dark-mid);
  transition: all var(--transition);
}

.card:hover {
  border-color: rgba(255, 255, 255, 0.15);
  transform: translateY(-2px);
}

.card-number {
  font-size: 3rem;
  font-weight: 200;
  color: var(--mid);
  margin-bottom: 1.5rem;
  line-height: 1;
}

.card h3 {
  margin-bottom: 0.75rem;
}

.card p {
  font-size: 0.95rem;
}

/* --- Dividers --- */
.divider {
  width: 100%;
  height: 1px;
  background: rgba(255, 255, 255, 0.06);
}

.divider-short {
  width: 60px;
  height: 1px;
  background: var(--gray);
  margin: 2rem 0;
}

/* --- Quote / Callout --- */
.callout {
  border-left: 1px solid var(--gray);
  padding-left: 2rem;
  margin: 3rem 0;
}

.callout p {
  font-size: 1.3rem;
  font-weight: 300;
  color: var(--off-white);
  font-style: italic;
  max-width: 700px;
  line-height: 1.6;
}

/* --- Stats row --- */
.stats-row {
  display: flex;
  gap: 4rem;
  padding: 3rem 0;
  border-top: 1px solid rgba(255, 255, 255, 0.06);
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
  margin: 4rem 0;
}

.stat {
  text-align: left;
}

.stat-number {
  font-size: 2.5rem;
  font-weight: 200;
  color: var(--white);
  line-height: 1;
  margin-bottom: 0.5rem;
}

.stat-label {
  font-size: 0.75rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--gray);
}

/* --- FAQ --- */
.faq-item {
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
  padding: 2rem 0;
}

.faq-item:first-child {
  border-top: 1px solid rgba(255, 255, 255, 0.06);
}

.faq-question {
  font-size: 1.15rem;
  font-weight: 400;
  color: var(--white);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  user-select: none;
}

.faq-question::after {
  content: '+';
  font-size: 1.5rem;
  font-weight: 200;
  color: var(--gray);
  transition: transform var(--transition);
}

.faq-item.open .faq-question::after {
  transform: rotate(45deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.4s ease, padding 0.4s ease;
}

.faq-item.open .faq-answer {
  max-height: 500px;
  padding-top: 1rem;
}

.faq-answer p {
  font-size: 0.95rem;
  line-height: 1.8;
}

/* --- Contact Form --- */
.form-group {
  margin-bottom: 1.5rem;
}

.form-group label {
  display: block;
  font-size: 0.75rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--gray);
  margin-bottom: 0.5rem;
}

.form-group input,
.form-group textarea,
.form-group select {
  width: 100%;
  padding: 1rem;
  background: var(--dark-mid);
  border: 1px solid rgba(255, 255, 255, 0.1);
  color: var(--white);
  font-family: var(--font-primary);
  font-size: 1rem;
  transition: border-color var(--transition);
  outline: none;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
  border-color: rgba(255, 255, 255, 0.3);
}

.form-group textarea {
  resize: vertical;
  min-height: 150px;
}

.form-group select option {
  background: var(--dark);
}

/* --- Footer --- */
footer {
  padding: 4rem 0;
  border-top: 1px solid rgba(255, 255, 255, 0.06);
}

.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.footer-content p {
  font-size: 0.8rem;
  color: var(--gray);
}

.footer-links {
  display: flex;
  gap: 2rem;
  list-style: none;
}

.footer-links a {
  font-size: 0.8rem;
  color: var(--gray);
  letter-spacing: 0.05em;
}

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

/* --- Scroll animations --- */
.fade-in {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.8s ease, transform 0.8s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* --- Case Study --- */
.case-study-card {
  padding: 3rem;
  border: 1px solid rgba(255, 255, 255, 0.06);
  background: var(--dark);
}

.case-tag {
  display: inline-block;
  padding: 0.3rem 0.8rem;
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  border: 1px solid rgba(255, 255, 255, 0.15);
  color: var(--gray);
  margin-right: 0.5rem;
  margin-bottom: 0.5rem;
}

/* --- Responsive --- */
@media (max-width: 900px) {
  nav {
    padding: 1.2rem 1.5rem;
  }

  .nav-toggle {
    display: block;
  }

  .nav-links {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    background: rgba(10, 10, 10, 0.97);
    padding: 2rem 1.5rem;
    gap: 1.5rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
  }

  .nav-links.open {
    display: flex;
  }

  .container {
    padding: 0 1.5rem;
  }

  section {
    padding: 5rem 0;
  }

  .grid-2,
  .grid-3 {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

  .stats-row {
    flex-direction: column;
    gap: 2rem;
  }

  .footer-content {
    flex-direction: column;
    gap: 1.5rem;
    text-align: center;
  }

  .hero {
    min-height: auto;
    padding-top: 10rem;
    padding-bottom: 5rem;
  }
}

@media (max-width: 600px) {
  h1 {
    font-size: 2rem;
  }

  h2 {
    font-size: 1.5rem;
  }

  .card {
    padding: 1.5rem;
  }
}