/* ============================================
   HYDRAULIK COURSE — Design System
   Industrial · Precise · Tactile
   ============================================ */

:root {
  /* Colors */
  --black: #0a0a0a;
  --ink: #1a1a1a;
  --graphite: #2a2a2a;
  --steel: #4a4a4a;
  --concrete: #8a8a8a;
  --bone: #f4f1ea;
  --paper: #faf8f3;
  --white: #ffffff;

  /* Accent palette — industrial */
  --oil: #ff8c1a;          /* hydraulic oil orange */
  --oil-dark: #c47100;
  --oil-light: #ffb84d;
  --steam: #5fb3d4;        /* cool blue for pressure indicators */
  --warning: #d4392e;      /* hazard red */
  --signal: #e6c419;       /* signal yellow */

  /* Typography */
  --font-display: 'Fraunces', Georgia, serif;
  --font-body: 'Space Grotesk', system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', 'Courier New', monospace;

  /* Spacing */
  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 2rem;
  --space-lg: 4rem;
  --space-xl: 8rem;

  /* Misc */
  --radius: 4px;
  --border: 1px solid var(--ink);
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.06);
  --shadow-md: 0 8px 24px rgba(0,0,0,0.08);
  --shadow-lg: 0 20px 60px rgba(0,0,0,0.12);
}

* { box-sizing: border-box; margin: 0; padding: 0; }

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

body {
  font-family: var(--font-body);
  background: var(--paper);
  color: var(--ink);
  line-height: 1.6;
  overflow-x: hidden;
}

a { color: inherit; text-decoration: none; }
em { font-style: italic; font-family: var(--font-display); font-weight: 700; }

/* ============================================
   NAVIGATION
   ============================================ */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 2rem;
  background: rgba(250, 248, 243, 0.92);
  backdrop-filter: blur(12px);
  border-bottom: var(--border);
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 0.95rem;
  letter-spacing: 0.02em;
}

.logo-mark {
  font-size: 1.4rem;
  color: var(--oil);
  animation: pulse 4s ease-in-out infinite;
}

.logo-dot { color: var(--oil); }

.nav-links {
  display: flex;
  gap: 2rem;
  align-items: center;
  font-size: 0.9rem;
}

.nav-links a {
  position: relative;
  transition: color 0.2s;
}

.nav-links a:hover { color: var(--oil); }

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--oil);
  transition: width 0.3s ease;
}

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

.github-link {
  padding: 0.4rem 0.9rem;
  border: 1px solid var(--ink);
  border-radius: var(--radius);
  font-family: var(--font-mono);
  font-size: 0.8rem !important;
}

.github-link:hover {
  background: var(--ink);
  color: var(--paper) !important;
}

.github-link::after { display: none !important; }

@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.7; transform: scale(0.95); }
}

/* ============================================
   HERO
   ============================================ */
.hero {
  position: relative;
  min-height: 90vh;
  padding: var(--space-lg) var(--space-md);
  display: flex;
  align-items: center;
  overflow: hidden;
}

.hero-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(26,26,26,0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(26,26,26,0.04) 1px, transparent 1px);
  background-size: 40px 40px;
  z-index: 0;
}

.hero-inner {
  position: relative;
  z-index: 2;
  max-width: 900px;
  width: 100%;
}

.hero-tag {
  display: inline-block;
  padding: 0.3rem 0.8rem;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  background: var(--ink);
  color: var(--paper);
  margin-bottom: 2rem;
  animation: slideUp 0.6s ease-out;
}

.hero-title {
  font-family: var(--font-display);
  font-size: clamp(2.5rem, 6vw, 5rem);
  font-weight: 900;
  line-height: 0.95;
  letter-spacing: -0.03em;
  margin-bottom: 2rem;
  animation: slideUp 0.7s ease-out 0.1s both;
}

.hero-accent {
  position: relative;
  color: var(--oil);
  font-style: italic;
}

.hero-accent::after {
  content: '';
  position: absolute;
  bottom: 0.05em;
  left: 0;
  width: 100%;
  height: 0.08em;
  background: var(--oil);
  opacity: 0.3;
}

.hero-sub {
  font-size: 1.2rem;
  color: var(--steel);
  max-width: 600px;
  margin-bottom: 2.5rem;
  animation: slideUp 0.7s ease-out 0.2s both;
}

.hero-cta {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  margin-bottom: 4rem;
  animation: slideUp 0.7s ease-out 0.3s both;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.9rem 1.6rem;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  border: 2px solid var(--ink);
  border-radius: var(--radius);
  transition: all 0.2s ease;
  cursor: pointer;
}

.btn-primary {
  background: var(--ink);
  color: var(--paper);
}

.btn-primary:hover {
  background: var(--oil);
  border-color: var(--oil);
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(255, 140, 26, 0.3);
}

.btn-secondary:hover {
  background: var(--ink);
  color: var(--paper);
}

.hero-stats {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  flex-wrap: wrap;
  animation: slideUp 0.7s ease-out 0.4s both;
}

.stat {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: var(--steel);
}

.stat b {
  color: var(--ink);
  font-size: 1.4rem;
  font-weight: 700;
}

.stat-divider {
  width: 1px;
  height: 24px;
  background: var(--concrete);
  opacity: 0.4;
}

.hero-visual {
  position: absolute;
  right: -100px;
  top: 50%;
  transform: translateY(-50%);
  width: 600px;
  height: 600px;
  opacity: 0.15;
  z-index: 1;
  pointer-events: none;
}

.gear-1 { transform-origin: 140px 200px; animation: spin 8s linear infinite; }
.gear-2 { transform-origin: 260px 200px; animation: spinReverse 8s linear infinite; }
.oil-flow circle { animation: dropDown 1.5s ease-in infinite; }
.oil-flow circle:nth-child(2) { animation-delay: 0.5s; }
.oil-flow circle:nth-child(3) { animation-delay: 1s; }
.oil-flow-out circle { animation: dropOut 1.5s ease-out infinite; }
.oil-flow-out circle:nth-child(2) { animation-delay: 0.5s; }
.oil-flow-out circle:nth-child(3) { animation-delay: 1s; }

@keyframes spin { to { transform: rotate(360deg); } }
@keyframes spinReverse { to { transform: rotate(-360deg); } }
@keyframes dropDown {
  0% { transform: translateY(-30px); opacity: 0; }
  50% { opacity: 1; }
  100% { transform: translateY(30px); opacity: 0; }
}
@keyframes dropOut {
  0% { transform: translateY(-10px); opacity: 0; }
  50% { opacity: 1; }
  100% { transform: translateY(40px); opacity: 0; }
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ============================================
   SECTIONS
   ============================================ */
.section {
  padding: var(--space-xl) var(--space-md);
  max-width: 1400px;
  margin: 0 auto;
}

.section-head {
  margin-bottom: var(--space-lg);
  max-width: 800px;
}

.section-num {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--concrete);
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--oil);
}

.section-num-light { color: rgba(255,255,255,0.6); }

.section h2 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 900;
  line-height: 1.05;
  letter-spacing: -0.02em;
  margin-bottom: 1.5rem;
}

.section-lead {
  font-size: 1.15rem;
  color: var(--steel);
}

.section-dark {
  background: var(--ink);
  color: var(--paper);
  max-width: none;
  padding: var(--space-xl) var(--space-md);
}

.section-dark .section-head { margin-left: auto; margin-right: auto; }
.section-dark .section-lead { color: rgba(244, 241, 234, 0.7); }

/* ============================================
   LEARNING PATH
   ============================================ */
.path {
  position: relative;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 2rem;
  padding: 2rem 0;
}

.path-line {
  position: absolute;
  top: 50%;
  left: 5%;
  right: 5%;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--oil), var(--oil), var(--oil-dark), transparent);
  z-index: 0;
}

.path-node {
  position: relative;
  z-index: 2;
  text-align: center;
  background: var(--paper);
  padding: 1.5rem 1rem;
}

.path-dot {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 60px;
  height: 60px;
  background: var(--paper);
  border: 2px solid var(--ink);
  border-radius: 50%;
  font-size: 1rem;
  margin-bottom: 1rem;
  transition: all 0.3s;
}

.path-node:hover .path-dot {
  background: var(--oil);
  border-color: var(--oil);
  transform: scale(1.1);
}

.path-content h3 {
  font-family: var(--font-display);
  font-size: 1.4rem;
  margin-bottom: 0.3rem;
}

.path-content p {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--oil-dark);
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.path-content small {
  color: var(--steel);
  font-size: 0.85rem;
}

/* ============================================
   MODULES GRID
   ============================================ */
.modules-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.5rem;
}

.module-card {
  position: relative;
  padding: 1.8rem;
  background: var(--white);
  border: var(--border);
  border-radius: var(--radius);
  transition: all 0.3s ease;
  overflow: hidden;
}

.module-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 4px;
  height: 100%;
  background: var(--concrete);
  transition: all 0.3s;
}

.module-card[data-level="1"]::before { background: #7fc97f; }
.module-card[data-level="2"]::before { background: #fdc086; }
.module-card[data-level="3"]::before { background: var(--oil); }
.module-card[data-level="4"]::before { background: var(--warning); }

.module-card::after {
  content: '→';
  position: absolute;
  top: 1.8rem;
  right: 1.8rem;
  font-size: 1.2rem;
  opacity: 0;
  transition: all 0.3s;
}

.module-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--ink);
}

.module-card:hover::before { width: 8px; }
.module-card:hover::after { opacity: 1; right: 1.4rem; }

.module-num {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--concrete);
  margin-bottom: 0.5rem;
}

.module-card h3 {
  font-family: var(--font-display);
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 0.6rem;
  padding-right: 1.5rem;
}

.module-card p {
  font-size: 0.9rem;
  color: var(--steel);
  margin-bottom: 1.2rem;
  line-height: 1.5;
}

.module-meta {
  display: flex;
  justify-content: space-between;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--concrete);
  padding-top: 1rem;
  border-top: 1px dashed var(--concrete);
}

/* ============================================
   FEATURES
   ============================================ */
.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}

.feature {
  display: block;
  padding: 2rem;
  background: rgba(255,255,255,0.04);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: var(--radius);
  transition: all 0.3s;
}

.feature:hover {
  background: rgba(255, 140, 26, 0.1);
  border-color: var(--oil);
  transform: translateY(-4px);
}

.feature-icon {
  font-size: 2.5rem;
  margin-bottom: 1rem;
  display: block;
}

.feature h3 {
  font-family: var(--font-display);
  font-size: 1.4rem;
  margin-bottom: 0.5rem;
}

.feature p {
  color: rgba(244, 241, 234, 0.7);
  font-size: 0.95rem;
  line-height: 1.5;
}

/* ============================================
   ABOUT
   ============================================ */
.section-about { padding-bottom: var(--space-xl); }

.about-grid {
  display: grid;
  grid-template-columns: 2fr 1fr;
  gap: 4rem;
  align-items: start;
}

.about-grid p {
  font-size: 1.05rem;
  color: var(--steel);
  margin-bottom: 1rem;
  max-width: 60ch;
}

.about-credits { margin-top: 2rem; }
.about-credits small {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--concrete);
  margin-bottom: 0.6rem;
}

.credits {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.credits span {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  padding: 0.3rem 0.7rem;
  background: var(--bone);
  border: 1px solid var(--concrete);
  border-radius: var(--radius);
}

.about-quote {
  position: sticky;
  top: 100px;
}

.about-quote blockquote {
  font-family: var(--font-display);
  font-size: 1.5rem;
  line-height: 1.3;
  font-style: italic;
  padding: 2rem;
  border-left: 4px solid var(--oil);
  background: var(--bone);
}

/* ============================================
   FOOTER
   ============================================ */
.footer {
  background: var(--ink);
  color: var(--paper);
  padding: var(--space-lg) var(--space-md) 2rem;
}

.footer-grid {
  max-width: 1400px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 3rem;
  margin-bottom: 3rem;
}

.footer h4 {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin-bottom: 1rem;
  color: var(--oil);
}

.footer a {
  display: block;
  font-size: 0.9rem;
  color: rgba(244, 241, 234, 0.7);
  margin-bottom: 0.5rem;
  transition: color 0.2s;
}

.footer a:hover { color: var(--oil); }
.footer p { font-size: 0.9rem; color: rgba(244, 241, 234, 0.7); margin-top: 1rem; }
.footer small { color: rgba(244, 241, 234, 0.5); font-size: 0.8rem; line-height: 1.8; }

.footer-bottom {
  max-width: 1400px;
  margin: 0 auto;
  padding-top: 2rem;
  border-top: 1px solid rgba(244, 241, 234, 0.1);
  text-align: center;
  font-family: var(--font-mono);
  color: rgba(244, 241, 234, 0.5);
}

/* ============================================
   RESPONSIVE
   ============================================ */
@media (max-width: 900px) {
  .nav-links { gap: 1rem; font-size: 0.85rem; }
  .nav-links a:not(.github-link) { display: none; }
  .nav-links a.github-link { display: inline-flex; }
  .hero-visual { display: none; }
  .about-grid { grid-template-columns: 1fr; }
  .about-quote { position: static; }
  .footer-grid { grid-template-columns: 1fr 1fr; gap: 2rem; }
  .path-line { display: none; }
}

@media (max-width: 600px) {
  .section { padding: 4rem 1.5rem; }
  .hero { padding: 3rem 1.5rem; }
  .hero-stats { gap: 1rem; }
  .stat-divider { display: none; }
  .footer-grid { grid-template-columns: 1fr; }
  .footer { padding: 3rem 1.5rem 2rem; }
}

/* ============================================
   LANGUAGE SWITCHER
   ============================================ */
.lang-switcher {
  display: flex;
  gap: 0;
  border: 1px solid var(--ink);
  border-radius: var(--radius);
  overflow: hidden;
}

.lang-btn {
  padding: 0.35rem 0.7rem;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  background: transparent;
  border: none;
  cursor: pointer;
  transition: all 0.2s;
  color: var(--steel);
}

.lang-btn:hover { background: rgba(255, 140, 26, 0.1); color: var(--ink); }
.lang-btn.active { background: var(--ink); color: var(--paper); }
.lang-btn + .lang-btn { border-left: 1px solid var(--ink); }