@import url('https://fonts.googleapis.com/css2?family=Noto+Serif+Bengali:wght@400;600;700&family=Hind+Siliguri:wght@300;400;500;600;700&family=Playfair+Display:ital,wght@0,400;0,600;0,700;1,400&family=Source+Serif+4:ital,opsz,wght@0,8..60,300;0,8..60,400;0,8..60,600;1,8..60,300;1,8..60,400&display=swap');

:root {
  --red: #B31942;
  --blue: #0A3161;
  --grey: #4A4A4A;
  --bg: #F9F7F4;
  --white: #ffffff;
  --border: #E0DBD4;
  --shadow: 0 2px 16px rgba(10,49,97,0.08);
  --radius: 10px;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: 'Hind Siliguri', 'Source Serif 4', Georgia, serif;
  background: var(--bg);
  color: var(--blue);
  font-size: 17px;
  line-height: 1.8;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

main {
  flex: 1;
}

h1, h2, h3, h4, h5, h6 {
  font-family: 'Noto Serif Bengali', 'Playfair Display', Georgia, serif;
  line-height: 1.35;
  color: var(--blue);
}

a { color: var(--blue); text-decoration: none; }
a:hover { color: var(--red); }

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

.container { max-width: 1100px; margin: 0 auto; padding: 0 2rem; }

/* ── Navbar ── */
.navbar {
  background: var(--white);
  border-bottom: 2px solid var(--border);
  padding: 0;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 8px rgba(10,49,97,0.06);
}

.navbar .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 70px;
}

.logo {
  font-family: 'Noto Serif Bengali', 'Playfair Display', Georgia, serif;
  font-size: 1.5rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
}

.logo .icon { color: var(--red); }
.logo .english { color: var(--blue); font-weight: 400; }
.logo .path { color: var(--red); font-weight: 700; }
.logo-img { height: 40px; width: auto; display: block; }

.nav-links {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  list-style: none;
}

.nav-links a {
  padding: 0.5rem 1rem;
  border-radius: var(--radius);
  font-size: 0.95rem;
  font-weight: 400;
  transition: background 0.15s, color 0.15s;
}

.nav-links a:hover { background: var(--bg); color: var(--red); }
.nav-links a.active { color: var(--red); font-weight: 600; }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.6rem 1.4rem;
  border-radius: var(--radius);
  font-family: 'Hind Siliguri', 'Source Serif 4', serif;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s;
  border: 2px solid transparent;
  text-decoration: none;
}

.btn-primary {
  background: var(--red);
  color: var(--white);
  border-color: transparent;
}
.btn-primary:hover { background: #97152f; border-color: transparent; color: var(--white); }

.btn-outline {
  background: transparent;
  color: var(--blue);
  border-color: var(--blue);
}
.btn-outline:hover { background: var(--blue); color: var(--white); }

.btn-install {
  background: transparent;
  color: var(--blue);
  border-color: var(--blue);
  font-size: 0.85rem;
  padding: 0.45rem 1rem;
  display: none;
}
.btn-install:hover { background: var(--blue); color: var(--white); }

/* ── Page header ── */
.page-header {
  background: var(--blue);
  color: var(--white);
  padding: 5rem 0 4rem;
  position: relative;
  overflow: hidden;
}

.page-header::before {
  content: '';
  position: absolute;
  top: 0; right: 0;
  width: 40%;
  height: 100%;
  background: rgba(179,25,66,0.08);
  clip-path: polygon(20% 0, 100% 0, 100% 100%, 0% 100%);
}

.page-header h1 { color: var(--white); font-size: 2.75rem; margin-bottom: 1rem; }
.page-header p { color: rgba(255,255,255,0.8); font-size: 1.1rem; max-width: 560px; }

/* ── Cards ── */
.card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: 0;
  padding: 2rem;
  box-shadow: var(--shadow);
  transition: box-shadow 0.2s, transform 0.2s;
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 22px), calc(100% - 22px) 100%, 0 100%);
}
.card:hover { box-shadow: 0 6px 28px rgba(10,49,97,0.13); transform: translateY(-2px); }

/* ── Alerts ── */
.alert {
  padding: 1rem 1.4rem;
  border-radius: var(--radius);
  border-left: 4px solid;
  font-size: 0.95rem;
  margin-bottom: 1.5rem;
}
.alert-success { background: #f0fdf4; border-color: #22c55e; color: #166534; }
.alert-error { background: #fff1f2; border-color: var(--red); color: var(--red); }
.alert-info { background: #eff6ff; border-color: var(--blue); color: var(--blue); }

/* ── Form controls ── */
.form-group { margin-bottom: 1.5rem; }
.form-label { display: block; font-weight: 600; margin-bottom: 0.5rem; font-size: 0.95rem; }
.form-control {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  font-family: 'Hind Siliguri', 'Source Serif 4', serif;
  font-size: 1rem;
  background: var(--white);
  color: var(--blue);
  transition: border-color 0.15s;
  outline: none;
}
.form-control:focus { border-color: var(--blue); }

/* ── Milestone badge ── */
.milestone-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  background: var(--red);
  color: var(--white);
  padding: 0.25rem 0.8rem;
  border-radius: 20px;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  text-transform: uppercase;
}

/* ── Spinner ── */
.spinner {
  width: 32px; height: 32px;
  border: 3px solid var(--border);
  border-top-color: var(--red);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
  margin: 3rem auto;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ── Footer ── */
footer {
  background: var(--blue);
  color: rgba(255,255,255,0.7);
  padding: 5rem 0 3rem;
  margin-top: 0;
  font-size: 0.9rem;
  position: relative;
  clip-path: ellipse(120% 100% at 50% 100%);
}
footer a { color: rgba(255,255,255,0.7); }
footer a:hover { color: var(--white); }
.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1.5rem;
  flex-wrap: wrap;
}
.footer-logo .english { color: rgba(255,255,255,0.9); }
.footer-logo .path { color: var(--red); }

/* ── Modal ── */
.modal-overlay {
  position: fixed; inset: 0;
  background: rgba(10,49,97,0.5);
  display: flex; align-items: center; justify-content: center;
  z-index: 999;
  backdrop-filter: blur(3px);
  opacity: 0; pointer-events: none;
  transition: opacity 0.2s;
}
.modal-overlay.open { opacity: 1; pointer-events: all; }
.modal {
  background: var(--white);
  border-radius: 14px;
  padding: 3rem;
  max-width: 460px;
  width: 90%;
  box-shadow: 0 20px 60px rgba(10,49,97,0.2);
  transform: translateY(20px);
  transition: transform 0.2s;
}
.modal-overlay.open .modal { transform: translateY(0); }
.modal-title {
  font-family: 'Noto Serif Bengali', 'Playfair Display', serif;
  font-size: 1.6rem;
  margin-bottom: 0.5rem;
}
.modal-close {
  position: absolute; top: 1rem; right: 1rem;
  background: none; border: none;
  font-size: 1.2rem; cursor: pointer; color: var(--grey);
  width: 36px; height: 36px;
  display: flex; align-items: center; justify-content: center;
  border-radius: 50%;
}
.modal-close:hover { background: var(--bg); }

/* ── Tabs ── */
.tab-nav {
  display: flex;
  gap: 0;
  border-bottom: 2px solid var(--border);
  margin-bottom: 2.5rem;
}
.tab-btn {
  padding: 0.75rem 1.5rem;
  background: none;
  border: none;
  border-bottom: 3px solid transparent;
  margin-bottom: -2px;
  font-family: 'Hind Siliguri', 'Source Serif 4', serif;
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--grey);
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s;
}
.tab-btn.active { color: var(--red); border-bottom-color: var(--red); }
.tab-btn:hover { color: var(--blue); }

/* ── Progress bar ── */
.progress-wrap {
  background: var(--border);
  border-radius: 20px;
  height: 8px;
  overflow: hidden;
}
.progress-bar {
  background: var(--red);
  height: 100%;
  border-radius: 20px;
  transition: width 0.4s ease;
}

/* ── Lock overlay ── */
.topic-locked {
  opacity: 0.55;
  cursor: not-allowed;
  pointer-events: none;
}
.lock-icon { color: var(--grey); font-size: 0.9rem; }

/* ── Utilities ── */
.text-red { color: var(--red); }
.text-blue { color: var(--blue); }
.text-grey { color: var(--grey); }
.text-muted { color: var(--grey); font-size: 0.9rem; }
.fw-bold { font-weight: 700; }
.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }
.mt-5 { margin-top: 3rem; }
.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }
.d-flex { display: flex; }
.align-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-1 { gap: 0.5rem; }
.gap-2 { gap: 1rem; }
.w-100 { width: 100%; }
.text-center { text-align: center; }

/* ── Hamburger ── */
.hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: flex-start;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.4rem;
  width: 36px;
  height: 36px;
}

.ham-line {
  display: block;
  height: 2px;
  background: var(--blue);
  border-radius: 2px;
  transition: transform 1s cubic-bezier(0.76, 0, 0.24, 1),
              opacity 1s ease,
              width 1s cubic-bezier(0.76, 0, 0.24, 1);
}
.ham-top { width: 24px; }
.ham-mid { width: 18px; }
.ham-bot { width: 24px; }

/* tap animation — top slides left, bot slides right, mid fades */
.hamburger.is-open .ham-top { transform: translateX(-6px); }
.hamburger.is-open .ham-mid { opacity: 0; transform: translateX(4px); }
.hamburger.is-open .ham-bot { transform: translateX(6px); }

/* ── Mobile drawer ── */
.mobile-menu {
  position: fixed;
  inset: 0;
  z-index: 200;
  visibility: hidden;
  pointer-events: none;
}
.mobile-menu.open {
  visibility: visible;
  pointer-events: all;
}

.mobile-menu-backdrop {
  position: absolute;
  inset: 0;
  background: rgba(10,49,97,0.45);
  backdrop-filter: blur(2px);
  opacity: 0;
  transition: opacity 0.4s ease;
}
.mobile-menu.open .mobile-menu-backdrop {
  opacity: 1;
}

.mobile-menu-panel {
  position: absolute;
  top: 0; right: 0;
  width: 280px;
  height: 100%;
  background: var(--white);
  box-shadow: -4px 0 24px rgba(10,49,97,0.15);
  display: flex;
  flex-direction: column;
  padding: 1.5rem;
  gap: 0.5rem;
  overflow-y: auto;
  transform: translateX(100%);
  transition: transform 0.5s cubic-bezier(0.76, 0, 0.24, 1);
}
.mobile-menu.open .mobile-menu-panel {
  transform: translateX(0);
}

.mobile-menu-close {
  align-self: flex-end;
  background: none;
  border: none;
  font-size: 1.3rem;
  cursor: pointer;
  color: var(--grey);
  padding: 0.25rem;
  margin-bottom: 0.75rem;
}

.mobile-menu-panel a,
.mobile-menu-panel button.mobile-nav-btn {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  padding: 0.85rem 1rem;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 500;
  color: var(--blue);
  text-decoration: none;
  border: none;
  background: none;
  cursor: pointer;
  font-family: 'Hind Siliguri', 'Source Serif 4', serif;
  width: 100%;
  text-align: left;
  transition: background 0.15s, color 0.15s;
}
.mobile-menu-panel a:hover,
.mobile-menu-panel button.mobile-nav-btn:hover { background: var(--bg); color: var(--red); }

.mobile-menu-divider {
  height: 1px;
  background: var(--border);
  margin: 0.5rem 0;
}

/* ── Responsive ── */
@media (max-width: 768px) {
  .container { padding: 0 1.25rem; }
  .page-header { padding: 3.5rem 0 3rem; }
  .page-header h1 { font-size: 2rem; }
  .nav-links { display: none; }
  .hamburger { display: flex; }
  .footer-inner { flex-direction: column; text-align: center; }
}