/* ============================================
   布局系统：容器 + 网格（Flexbox回退 + CSS Grid）
   ============================================ */

/* --- 容器 --- */
.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-pad);
  width: 100%;
}

/* --- 区块间距 --- */
.section {
  padding: var(--sp-section) 0;
}

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

/* --- Flexbox 网格（IE11回退） --- */
.grid {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -ms-flex-wrap: wrap;
  flex-wrap: wrap;
  gap: var(--sp-xl);
}

.grid--2 > * {
  -webkit-box-flex: 0;
  -ms-flex: 0 0 calc(50% - 1rem);
  flex: 0 0 calc(50% - 1rem);
  max-width: calc(50% - 1rem);
}

.grid--3 > * {
  -webkit-box-flex: 0;
  -ms-flex: 0 0 calc(33.333% - 1.34rem);
  flex: 0 0 calc(33.333% - 1.34rem);
  max-width: calc(33.333% - 1.34rem);
}

.grid--4 > * {
  -webkit-box-flex: 0;
  -ms-flex: 0 0 calc(25% - 1.5rem);
  flex: 0 0 calc(25% - 1.5rem);
  max-width: calc(25% - 1.5rem);
}

/* CSS Grid 增强（现代浏览器） */
@supports (display: grid) {
  .grid {
    display: grid;
    gap: var(--sp-xl);
  }
  .grid > * {
    -ms-flex: unset;
    flex: unset;
    max-width: unset;
  }
  .grid--2 { grid-template-columns: repeat(2, 1fr); }
  .grid--3 { grid-template-columns: repeat(3, 1fr); }
  .grid--4 { grid-template-columns: repeat(4, 1fr); }
}

/* --- 两栏图文布局 --- */
.split {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: center;
  -ms-flex-align: center;
  align-items: center;
  gap: var(--sp-3xl);
}

.split__content,
.split__media {
  -webkit-box-flex: 1;
  -ms-flex: 1;
  flex: 1;
}

.split--reverse { -webkit-box-orient: horizontal; -webkit-box-direction: reverse; -ms-flex-direction: row-reverse; flex-direction: row-reverse; }

/* --- 响应式 --- */
@media (max-width: 1023px) {
  .grid--3 > * {
    -ms-flex: 0 0 calc(50% - 1rem);
    flex: 0 0 calc(50% - 1rem);
    max-width: calc(50% - 1rem);
  }
  .grid--4 > * {
    -ms-flex: 0 0 calc(50% - 1rem);
    flex: 0 0 calc(50% - 1rem);
    max-width: calc(50% - 1rem);
  }

  @supports (display: grid) {
    .grid--3 { grid-template-columns: repeat(2, 1fr); }
    .grid--4 { grid-template-columns: repeat(2, 1fr); }
  }
}

@media (max-width: 767px) {
  .section { padding: var(--sp-3xl) 0; }

  .grid--2 > *,
  .grid--3 > *,
  .grid--4 > * {
    -ms-flex: 0 0 100%;
    flex: 0 0 100%;
    max-width: 100%;
  }

  @supports (display: grid) {
    .grid--2,
    .grid--3,
    .grid--4 { grid-template-columns: 1fr; }
  }

  .split {
    -webkit-box-orient: vertical;
    -webkit-box-direction: normal;
    -ms-flex-direction: column;
    flex-direction: column;
    gap: var(--sp-2xl);
  }

  .split--reverse { -webkit-box-direction: normal; -ms-flex-direction: column; flex-direction: column; }
}