/* ============================================================
   基础层：重置 + 中文排版基线
   ============================================================ */

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

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--topbar-h) + var(--sp-4));
}

body {
  margin: 0;
  min-height: 100vh;
  background-color: var(--c-bg);
  color: var(--c-text);
  font-family: var(--font-sans);
  font-size: var(--fs-body);
  font-weight: 400;
  line-height: var(--lh-body);
  letter-spacing: var(--tracking-tight);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow: hidden; /* 滚动交给内容区，保证侧栏与顶栏固定 */
}

h1,
h2,
h3,
h4,
h5,
h6 {
  margin: 0;
  font-weight: 600;
  line-height: var(--lh-tight);
  letter-spacing: var(--tracking-tight);
}

p {
  margin: 0;
}

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

a:hover {
  color: var(--c-accent-2);
}

button {
  font: inherit;
  color: inherit;
  background: none;
  border: 0;
  padding: 0;
  cursor: pointer;
}

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

ul,
ol {
  margin: 0;
  padding: 0;
  list-style: none;
}

table {
  border-collapse: collapse;
  border-spacing: 0;
}

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

code,
kbd,
samp {
  font-family: var(--font-mono);
  font-size: 0.92em;
}

/* ---------- 选中态 ---------- */
::selection {
  background: var(--selection-bg);
  color: var(--c-text);
}

/* ---------- 滚动条 ---------- */
::-webkit-scrollbar {
  width: 10px;
  height: 10px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

::-webkit-scrollbar-thumb {
  background: var(--c-border-strong);
  border-radius: var(--r-pill);
  border: 2px solid transparent;
  background-clip: content-box;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--c-text-4);
  background-clip: content-box;
}

/* ---------- 焦点可见性（键盘导航） ---------- */
:focus-visible {
  outline: 2px solid var(--c-accent);
  outline-offset: 2px;
  border-radius: var(--r-xs);
}

/* ---------- 工具类 ---------- */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.is-hidden {
  display: none !important;
}

/* ---------- 尊重降低动效偏好 ---------- */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}