:root {
  --bg: #f8fafc;
  --surface: #ffffff;
  --surface-soft: #f1f5f9;
  --text: #0f172a;
  --muted: #475569;
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --accent: #f59e0b;
  --success: #16a34a;
  --shadow: 0 10px 30px rgba(15, 23, 42, 0.08);
}

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

body {
  font-family: Inter, system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background: radial-gradient(circle at top, #dbeafe 0%, var(--bg) 35%);
  color: var(--text);
  line-height: 1.6;
}

.container {
  width: min(980px, 92vw);
  margin: 0 auto;
}

header {
  background: linear-gradient(120deg, var(--primary-dark), var(--primary));
  color: white;
  position: sticky;
  top: 0;
  z-index: 10;
  box-shadow: 0 6px 20px rgba(37, 99, 235, 0.35);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 14px 0;
}

.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
}

.logo-icon {
  width: 28px;
  height: 28px;
}

.menu-btn {
  border: 1px solid rgba(255, 255, 255, 0.5);
  background: transparent;
  color: #fff;
  border-radius: 8px;
  padding: 6px 10px;
  font-size: 0.9rem;
}

nav {
  display: none;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 12px;
}

nav.open {
  display: flex;
}

nav a {
  color: white;
  text-decoration: none;
  padding: 8px 10px;
  border-radius: 8px;
  transition: 0.2s ease;
}

nav a:hover,
nav a.active {
  background: rgba(255, 255, 255, 0.2);
}

main {
  padding: 22px 0 30px;
}

.section,
.hero {
  background: var(--surface);
  border-radius: 14px;
  box-shadow: var(--shadow);
  padding: 18px;
  margin-bottom: 16px;
}

.hero h1,
.hero h2,
.section h2,
.section h3 {
  margin-bottom: 10px;
}

.hero p,
.section p {
  color: var(--muted);
}

.grid {
  display: grid;
  gap: 12px;
}

.card {
  background: var(--surface-soft);
  border: 1px solid #e2e8f0;
  border-radius: 12px;
  padding: 12px;
}

.card h4 {
  margin-bottom: 6px;
}

.button,
button.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  background: var(--primary);
  color: white;
  text-decoration: none;
  border: none;
  border-radius: 9px;
  padding: 10px 14px;
  margin-top: 10px;
  cursor: pointer;
  transition: 0.2s ease;
}

.button:hover,
button.button:hover {
  background: var(--primary-dark);
}

.highlight {
  border-left: 4px solid var(--accent);
}

.progress {
  width: 100%;
  height: 10px;
  background: #dbeafe;
  border-radius: 999px;
  overflow: hidden;
  margin-top: 8px;
}

.progress > span {
  display: block;
  height: 100%;
  width: 0;
  background: var(--success);
  transition: width 0.25s ease;
}

.accordion-item {
  border: 1px solid #dbe3ee;
  border-radius: 10px;
  margin-bottom: 10px;
  overflow: hidden;
}

.accordion-trigger {
  width: 100%;
  text-align: left;
  background: #eff6ff;
  border: none;
  padding: 12px;
  font-weight: 600;
  cursor: pointer;
}

.accordion-panel {
  display: none;
  padding: 12px;
  background: #fff;
}

.accordion-item.open .accordion-panel {
  display: block;
}

.tip {
  border-left: 4px solid var(--primary);
  padding-left: 10px;
  margin-top: 6px;
}

footer {
  margin-top: 20px;
  padding: 24px 0;
  text-align: center;
  color: #64748b;
}

@media (min-width: 768px) {
  .menu-btn {
    display: none;
  }

  nav {
    display: flex;
    flex-direction: row;
    margin: 0;
  }

  .grid.two {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .grid.three {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}