/* Arvea — base：reset、排版、容器、按钮、通用块 */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: auto;
}

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font);
  font-size: var(--text-body);
  line-height: var(--leading-body);
  letter-spacing: var(--tracking-snug);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

h1,
h2,
h3,
h4 {
  margin: 0;
  font-weight: 600;
  line-height: var(--leading-snug);
  letter-spacing: var(--tracking-tight);
  text-wrap: balance;
}

h1 {
  font-size: var(--text-hero);
  line-height: var(--leading-tight);
}

h2 {
  font-size: var(--text-h2);
}

h3 {
  font-size: var(--text-h3);
}

p {
  margin: 0;
  text-wrap: pretty;
}

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

a:hover {
  text-decoration: underline;
  text-underline-offset: 0.2em;
}

button,
input,
select,
textarea {
  font: inherit;
  color: inherit;
}

:focus-visible {
  outline: 2px solid var(--blue);
  outline-offset: 4px;
  border-radius: 4px;
}

::selection {
  background: var(--blue);
  color: #fff;
}

/* 布局 */
.container {
  width: min(100% - var(--gutter) * 2, var(--container));
  margin-inline: auto;
}

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

.stack > * + * {
  margin-block-start: var(--space-4);
}

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

.section-dark a {
  color: var(--blue-bright);
}

/* 文字层级 */
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  margin: 0;
  color: var(--blue);
  font-size: var(--text-small);
  font-weight: 600;
  letter-spacing: 0.02em;
}

.eyebrow::before {
  content: "";
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: currentColor;
}

.section-dark .eyebrow {
  color: var(--blue-bright);
}

.lede {
  color: var(--muted);
  font-size: var(--text-lede);
  line-height: 1.6;
  letter-spacing: -0.01em;
}

.section-dark .lede,
.section-dark .muted {
  color: var(--night-muted);
}

.muted {
  color: var(--muted);
}

.small {
  font-size: var(--text-small);
}

/* 按钮 */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  min-height: 2.75rem;
  padding: 0.65rem 1.4rem;
  border: 1px solid transparent;
  border-radius: var(--radius-pill);
  font-size: 1rem;
  font-weight: 500;
  line-height: 1.2;
  text-decoration: none;
  transition: background-color var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease),
    color var(--dur-fast) var(--ease), transform var(--dur-fast) var(--ease);
}

.btn:hover {
  text-decoration: none;
}

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

.btn-primary:hover {
  background: var(--blue-hover);
}

.btn-primary:active {
  transform: scale(0.985);
}

.btn-ghost {
  border-color: var(--line);
  color: var(--ink);
  background: transparent;
}

.btn-ghost:hover {
  border-color: var(--ink);
}

.section-dark .btn-ghost {
  border-color: var(--night-line);
  color: var(--night-text);
}

.section-dark .btn-ghost:hover {
  border-color: var(--night-text);
}

.link-arrow {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 1rem;
  font-weight: 500;
}

.link-arrow span {
  transition: transform var(--dur-fast) var(--ease);
}

.link-arrow:hover {
  text-decoration: none;
}

.link-arrow:hover span {
  transform: translateX(3px);
}

/* 可访问性 */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

.skip-link {
  position: absolute;
  inset-inline-start: 1rem;
  inset-block-start: -4rem;
  z-index: 200;
  padding: 0.6rem 1rem;
  border-radius: var(--radius-sm);
  background: var(--ink);
  color: #fff;
  transition: inset-block-start var(--dur-fast) var(--ease);
}

.skip-link:focus {
  inset-block-start: 0.75rem;
}

/* 滚动显现（默认可见，JS 加上 .js 后才隐藏） */
.js .reveal {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity var(--dur-slow) var(--ease), transform var(--dur-slow) var(--ease);
}

.js .reveal.is-in {
  opacity: 1;
  transform: none;
}

@media (prefers-reduced-motion: reduce) {
  .js .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }
}