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

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-height) + 12px);
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-stack);
  font-size: var(--text-body);
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

a {
  color: var(--color-accent);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

::selection {
  background: rgba(0, 113, 227, 0.2);
}

/* ---------- 通用排版 ---------- */

.container {
  width: 100%;
  max-width: var(--container-wide);
  margin-inline: auto;
  padding-inline: clamp(1.25rem, 4vw, 2.5rem);
}

.container--text {
  max-width: var(--container-text);
}

.section {
  padding-block: var(--space-section);
}

.section--alt {
  background: var(--color-bg-alt);
}

.section--dark {
  background: var(--color-bg-dark);
  color: var(--color-text-on-dark);
}

.eyebrow {
  display: block;
  font-size: var(--text-caption);
  font-weight: 600;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-accent);
  margin-bottom: 1.1rem;
}

.section--dark .eyebrow {
  color: var(--color-link-on-dark);
}

.headline {
  font-size: var(--text-headline);
  font-weight: 700;
  letter-spacing: -0.015em;
  line-height: 1.08;
}

.headline--gradient {
  background: var(--gradient-hero);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  /* 渐变文字行高过紧会裁掉汉字下缘 */
  padding-bottom: 0.08em;
}

.section-sub {
  font-size: var(--text-sub);
  font-weight: 400;
  color: var(--color-text-secondary);
  max-width: 38em;
  margin-top: 1.25rem;
  line-height: 1.5;
}

.section--dark .section-sub {
  color: var(--color-text-secondary-on-dark);
}

.section-head {
  margin-bottom: var(--space-headline-gap);
}

.section-head--center {
  text-align: center;
}

.section-head--center .section-sub {
  margin-inline: auto;
}

/* ---------- 按钮与链接 ---------- */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4em;
  font-size: 1.0625rem;
  font-weight: 500;
  line-height: 1;
  padding: 0.85em 1.5em;
  border-radius: var(--radius-pill);
  transition: background-color var(--duration-reveal, 0.3s) ease, transform 0.3s var(--ease-out-expo);
}

.btn--primary {
  background: var(--color-accent);
  color: #fff;
}

.btn--primary:hover {
  background: var(--color-accent-hover);
  text-decoration: none;
}

.btn--ghost {
  color: var(--color-accent);
  border: 1px solid var(--color-accent);
}

.btn--ghost:hover {
  background: var(--color-accent);
  color: #fff;
  text-decoration: none;
}

.btn:active {
  transform: scale(0.97);
}

.link-more {
  font-size: 1.0625rem;
  font-weight: 500;
}

.link-more::after {
  content: " ›";
  font-weight: 600;
}

/* ---------- 滚动浮现 ---------- */

.reveal {
  opacity: 0;
  transform: translateY(28px);
  transition: opacity var(--duration-reveal) var(--ease-out-expo),
    transform var(--duration-reveal) var(--ease-out-expo);
  transition-delay: var(--reveal-delay, 0s);
  will-change: opacity, transform;
}

.reveal.is-visible {
  opacity: 1;
  transform: none;
  will-change: auto;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .btn,
  .btn:active {
    transition: none;
    transform: none;
  }
}