/* ============================================================
   Biodegradable Technology – Site-wide Stylesheet
   ============================================================ */

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

:root {
  --green-dark:  #1b5e20;
  --green-mid:   #2e7d32;
  --green-light: #43a047;
  --green-pale:  #e8f5e9;
  --teal:        #00695c;
  --teal-light:  #e0f2f1;
  --amber:       #f57f17;
  --amber-light: #fff8e1;
  --text:        #212121;
  --text-muted:  #616161;
  --surface:     #ffffff;
  --border:      #c8e6c9;
  --shadow:      0 2px 12px rgba(0,0,0,.10);
  --radius:      10px;
  --nav-h:       64px;
  --max-w:       1120px;
  --font-body:   'Segoe UI', system-ui, sans-serif;
  --font-heading:'Georgia', serif;
  --transition:  .25s ease;
}

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  color: var(--text);
  background: #f9fbe7;
  line-height: 1.7;
  font-size: 1rem;
}

img { max-width: 100%; height: auto; display: block; }
a   { color: var(--green-mid); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--green-dark); text-decoration: underline; }

/* ---------- Layout helpers ---------- */
.container   { max-width: var(--max-w); margin: 0 auto; padding: 0 1.25rem; }
.section     { padding: 4rem 0; }
.section--alt { background: var(--green-pale); }
.section--teal{ background: var(--teal-light); }
.text-center { text-align: center; }
.visually-hidden { position: absolute; width: 1px; height: 1px; clip: rect(0,0,0,0); overflow: hidden; }

/* ---------- Typography ---------- */
h1, h2, h3, h4 {
  font-family: var(--font-heading);
  line-height: 1.25;
  color: var(--green-dark);
}
h1 { font-size: clamp(2rem, 5vw, 3.2rem); }
h2 { font-size: clamp(1.5rem, 3.5vw, 2.2rem); margin-bottom: 1rem; }
h3 { font-size: 1.3rem; margin-bottom: .5rem; }
h4 { font-size: 1.1rem; margin-bottom: .4rem; }
p  { margin-bottom: 1rem; }
p:last-child { margin-bottom: 0; }

.section-heading {
  text-align: center;
  margin-bottom: 2.5rem;
}
.section-heading p {
  color: var(--text-muted);
  max-width: 680px;
  margin: .5rem auto 0;
  font-size: 1.05rem;
}

/* ---------- Top navigation ---------- */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 200;
  background: var(--green-dark);
  height: var(--nav-h);
  box-shadow: 0 2px 8px rgba(0,0,0,.25);
}
.site-nav .container {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}
.nav-brand {
  color: #fff;
  font-family: var(--font-heading);
  font-size: 1.2rem;
  font-weight: bold;
  white-space: nowrap;
  flex-shrink: 0;
}
.nav-brand span { color: #a5d6a7; }
.nav-brand:hover { color: #fff; text-decoration: none; }

.nav-links {
  display: flex;
  list-style: none;
  gap: .25rem;
  flex-wrap: wrap;
  justify-content: flex-end;
}
.nav-links a {
  color: #c8e6c9;
  padding: .35rem .7rem;
  border-radius: 6px;
  font-size: .92rem;
  transition: background var(--transition), color var(--transition);
  white-space: nowrap;
}
.nav-links a:hover,
.nav-links a.active {
  background: var(--green-light);
  color: #fff;
  text-decoration: none;
}

/* Hamburger */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: .4rem;
  color: #fff;
  font-size: 1.5rem;
  line-height: 1;
}

/* ---------- Hero ---------- */
.hero {
  background: linear-gradient(135deg, var(--green-dark) 0%, var(--teal) 100%);
  color: #fff;
  padding: 5rem 0 4rem;
  text-align: center;
  position: relative;
  overflow: hidden;
}
.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at 20% 80%, rgba(255,255,255,.06) 0%, transparent 50%),
    radial-gradient(circle at 80% 20%, rgba(255,255,255,.08) 0%, transparent 50%);
}
.hero .container { position: relative; z-index: 1; }
.hero h1 { color: #fff; margin-bottom: 1rem; }
.hero .subtitle {
  font-size: clamp(1rem, 2.5vw, 1.25rem);
  color: #c8e6c9;
  max-width: 700px;
  margin: 0 auto 2rem;
}
.hero-badge {
  display: inline-block;
  background: rgba(255,255,255,.15);
  border: 1px solid rgba(255,255,255,.3);
  padding: .35rem 1rem;
  border-radius: 999px;
  font-size: .85rem;
  margin-bottom: 1.25rem;
  letter-spacing: .05em;
  text-transform: uppercase;
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-block;
  padding: .75rem 1.75rem;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: .95rem;
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition), background var(--transition);
  text-decoration: none;
}
.btn:hover { transform: translateY(-2px); box-shadow: 0 6px 20px rgba(0,0,0,.15); text-decoration: none; }
.btn-primary {
  background: var(--green-light);
  color: #fff;
}
.btn-primary:hover { background: var(--green-mid); color: #fff; }
.btn-outline {
  background: transparent;
  border: 2px solid #fff;
  color: #fff;
}
.btn-outline:hover { background: rgba(255,255,255,.15); color: #fff; }
.btn-group { display: flex; gap: 1rem; flex-wrap: wrap; justify-content: center; margin-top: 1.5rem; }

/* ---------- Cards ---------- */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.5rem;
}
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.75rem;
  box-shadow: var(--shadow);
  transition: transform var(--transition), box-shadow var(--transition);
}
.card:hover { transform: translateY(-4px); box-shadow: 0 8px 28px rgba(0,0,0,.13); }
.card-icon {
  font-size: 2.5rem;
  margin-bottom: .75rem;
  display: block;
}
.card h3 { color: var(--green-mid); }

/* ---------- Fact boxes ---------- */
.fact-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 1rem;
}
.fact-box {
  background: var(--surface);
  border-left: 5px solid var(--green-light);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  box-shadow: var(--shadow);
}
.fact-box .number {
  font-size: 2rem;
  font-weight: 700;
  color: var(--green-mid);
  line-height: 1;
  margin-bottom: .25rem;
}
.fact-box .label {
  font-size: .88rem;
  color: var(--text-muted);
}

/* ---------- Two-column feature rows ---------- */
.feature-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
  align-items: center;
  margin-bottom: 3.5rem;
}
.feature-row:last-child { margin-bottom: 0; }
.feature-row.reverse .feature-text { order: 2; }
.feature-row.reverse .feature-visual { order: 1; }
.feature-visual {
  background: var(--green-pale);
  border-radius: var(--radius);
  padding: 2.5rem;
  text-align: center;
  border: 1px solid var(--border);
}
.feature-visual .big-icon { font-size: 6rem; display: block; margin-bottom: 1rem; }
.feature-visual p { color: var(--text-muted); font-style: italic; font-size: .92rem; }

/* ---------- Timeline ---------- */
.timeline { position: relative; padding-left: 2rem; }
.timeline::before {
  content: '';
  position: absolute;
  left: 7px;
  top: 0; bottom: 0;
  width: 3px;
  background: var(--green-light);
  border-radius: 99px;
}
.timeline-item {
  position: relative;
  margin-bottom: 2rem;
}
.timeline-item::before {
  content: '';
  position: absolute;
  left: -2rem;
  top: .35rem;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--green-light);
  border: 3px solid #fff;
  box-shadow: 0 0 0 2px var(--green-light);
}
.timeline-year {
  font-weight: 700;
  color: var(--green-mid);
  font-size: .88rem;
  text-transform: uppercase;
  letter-spacing: .07em;
  margin-bottom: .2rem;
}

/* ---------- Callout / highlight ---------- */
.callout {
  border-left: 5px solid var(--green-light);
  background: var(--green-pale);
  padding: 1.25rem 1.5rem;
  border-radius: 0 var(--radius) var(--radius) 0;
  margin: 1.5rem 0;
}
.callout.amber {
  border-left-color: var(--amber);
  background: var(--amber-light);
}
.callout.teal {
  border-left-color: var(--teal);
  background: var(--teal-light);
}

/* ---------- Source / citation boxes ---------- */
.source-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: .75rem;
}
.source-list li {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem 1.25rem;
  box-shadow: var(--shadow);
  font-size: .92rem;
}
.source-list li a { font-weight: 600; }
.source-tag {
  display: inline-block;
  background: var(--green-light);
  color: #fff;
  border-radius: 999px;
  font-size: .72rem;
  padding: .1rem .6rem;
  margin-right: .4rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: .05em;
}

/* ---------- Table ---------- */
.data-table-wrap { overflow-x: auto; }
.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: .93rem;
}
.data-table th, .data-table td {
  padding: .75rem 1rem;
  border: 1px solid var(--border);
  text-align: left;
}
.data-table th {
  background: var(--green-mid);
  color: #fff;
  font-weight: 600;
}
.data-table tr:nth-child(even) td { background: var(--green-pale); }

/* ---------- Breadcrumb ---------- */
.breadcrumb {
  padding: .75rem 0;
  font-size: .85rem;
  color: var(--text-muted);
}
.breadcrumb a { color: var(--green-mid); }
.breadcrumb span::before { content: ' › '; }

/* ---------- Page hero (inner pages) ---------- */
.page-hero {
  background: linear-gradient(135deg, var(--green-dark) 0%, var(--teal) 100%);
  color: #fff;
  padding: 3.5rem 0 3rem;
}
.page-hero h1 { color: #fff; margin-bottom: .6rem; font-size: clamp(1.7rem, 4vw, 2.6rem); }
.page-hero p  { color: #c8e6c9; font-size: 1.05rem; max-width: 640px; }

/* ---------- Footer ---------- */
.site-footer {
  background: var(--green-dark);
  color: #a5d6a7;
  padding: 3rem 0 1.5rem;
  margin-top: 4rem;
}
.footer-grid {
  display: grid;
  grid-template-columns: 2fr repeat(3, 1fr);
  gap: 2rem;
  margin-bottom: 2rem;
}
.footer-brand { color: #fff; font-family: var(--font-heading); font-size: 1.1rem; margin-bottom: .5rem; }
.footer-brand span { color: #a5d6a7; }
.site-footer h4 { color: #fff; font-size: .95rem; margin-bottom: .75rem; }
.footer-links { list-style: none; display: flex; flex-direction: column; gap: .35rem; }
.footer-links a { color: #a5d6a7; font-size: .9rem; }
.footer-links a:hover { color: #fff; text-decoration: underline; }
.footer-bottom {
  border-top: 1px solid rgba(255,255,255,.15);
  padding-top: 1.25rem;
  font-size: .82rem;
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: .5rem;
  color: #81c784;
}

/* ---------- Skip link ---------- */
.skip-link {
  position: absolute;
  top: -9999px;
  left: 1rem;
  background: var(--green-dark);
  color: #fff;
  padding: .5rem 1rem;
  border-radius: 0 0 var(--radius) var(--radius);
  font-size: .9rem;
  z-index: 999;
}
.skip-link:focus { top: 0; }

/* ---------- Utility: tag pills ---------- */
.tag {
  display: inline-block;
  background: var(--green-pale);
  border: 1px solid var(--border);
  color: var(--green-dark);
  padding: .2rem .75rem;
  border-radius: 999px;
  font-size: .8rem;
  font-weight: 600;
}

/* ---------- Progress / bar ---------- */
.progress-bar-wrap {
  background: #c8e6c9;
  border-radius: 999px;
  height: 10px;
  margin-top: .5rem;
}
.progress-bar {
  height: 100%;
  border-radius: 999px;
  background: var(--green-light);
  transition: width 1s ease;
}

/* ---------- Responsive ---------- */
@media (max-width: 900px) {
  .feature-row { grid-template-columns: 1fr; gap: 1.5rem; }
  .feature-row.reverse .feature-text { order: unset; }
  .feature-row.reverse .feature-visual { order: unset; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 700px) {
  .nav-links { display: none; flex-direction: column; width: 100%; }
  .nav-links.open {
    display: flex;
    position: fixed;
    top: var(--nav-h);
    left: 0;
    right: 0;
    background: var(--green-dark);
    padding: 1rem;
    z-index: 190;
    gap: .25rem;
  }
  .nav-toggle { display: block; }
  .footer-grid { grid-template-columns: 1fr; }
  .footer-bottom { flex-direction: column; text-align: center; }
  .card-grid { grid-template-columns: 1fr; }
  .fact-grid { grid-template-columns: 1fr 1fr; }
}