* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
}

body {
  background: #0b0f1a;
  color: #e5e7eb;
  min-height: 100vh;
}

.bg {
  position: fixed;
  inset: 0;
  background:
    radial-gradient(circle at top, rgba(59,130,246,.25), transparent 60%),
    radial-gradient(circle at bottom, rgba(37,99,235,.2), transparent 60%);
  z-index: -1;
}

.container {
  max-width: 480px;
  margin: 0 auto;
  padding: 24px 16px 60px;
}

.title {
  text-align: center;
  font-size: 28px;
  font-weight: 700;
  margin-bottom: 24px;
  color: #eaf1ff;
}

/* Accordion */
.accordion {
  background: rgba(255,255,255,0.04);
  border-radius: 20px;
  overflow: hidden;
  box-shadow: 0 20px 50px rgba(0,0,0,.4);
}

.accordion-item + .accordion-item {
  border-top: 1px solid rgba(255,255,255,0.06);
}

.accordion-header {
  width: 100%;
  background: transparent;
  border: none;
  color: #e5e7eb;
  padding: 18px 20px;
  font-size: 16px;
  font-weight: 600;
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
}

.arrow {
  width: 8px;
  height: 8px;
  border-right: 2px solid #60a5fa;
  border-bottom: 2px solid #60a5fa;
  transform: rotate(45deg);
  transition: transform .3s ease;
}

.accordion-item.active .arrow {
  transform: rotate(-135deg);
}

.accordion-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height .35s ease;
  background: rgba(255,255,255,0.03);
}

.accordion-content a {
  display: block;
  padding: 14px 20px;
  color: #c7d2fe;
  text-decoration: none;
  font-size: 15px;
  border-top: 1px solid rgba(255,255,255,0.05);
}

.accordion-content a:hover {
  background: rgba(59,130,246,.15);
}

/* Tablet */
@media (min-width: 768px) {
  .container {
    max-width: 600px;
  }
  .title {
    font-size: 32px;
  }
}

/* Desktop */
@media (min-width: 1024px) {
  .container {
    max-width: 720px;
  }
}

/* Вкладки раздела «Оптимизация веб-приложений» */
.tabs {
  display: flex;
  gap: 8px;
  padding: 12px;
  border-bottom: 1px solid rgba(255,255,255,0.06);
}

.tab-button {
  flex: 1;
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 10px;
  padding: 10px 12px;
  background: rgba(255,255,255,0.04);
  color: #aeb9d3;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  transition: .2s ease;
}

.tab-button:hover {
  background: rgba(59,130,246,.12);
  color: #e5e7eb;
}

.tab-button.active {
  background: rgba(59,130,246,.18);
  border-color: rgba(96,165,250,.45);
  color: #eaf1ff;
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

@media (max-width: 480px) {
  .tabs {
    flex-direction: column;
  }
}