:root {
  --primary: #2563eb;
  --primary-dark: #1e40af;
  --accent: #2563eb;
  --bg: #f5f6fa;
  --text: #222;
  --text-light: #fff;
  --card: #fff;
  --card-dark: #23272f;
  --border: #e5e7eb;
  --radius: 8px;
  --shadow: 0 2px 12px rgba(30, 64, 175, 0.06);
  --transition: 0.18s cubic-bezier(.4,0,.2,1);
  --header-height: 60px;

  /* 下拉面板内部可调内边距 */
  --dropdown-padding-vertical: 0.5rem;
  --dropdown-padding-horizontal: 0.8rem;
}

html, body {
  height: 100%;
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI','Microsoft YaHei',Arial,sans-serif;
  background: var(--bg);
  color: var(--text);
  font-size: 16px;
  letter-spacing: 0.01em;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

header {
  background: #fff;
  color: var(--primary-dark);
  padding: 0;
  box-shadow: 0 2px 8px rgba(30,64,175,0.04);
  border-radius: 0 0 var(--radius) var(--radius);
  min-height: var(--header-height);
  display: flex;
  align-items: center;
  animation: fadeInDown 0.5s cubic-bezier(.4,0,.2,1);
}

header-red {
  background: #ff0000;
  color: var(--primary-dark);
  padding: 0;
  box-shadow: 0 2px 8px rgba(30,64,175,0.04);
  border-radius: 0 0 var(--radius) var(--radius);
  min-height: var(--header-height);
  display: flex;
  align-items: center;
  animation: fadeInDown 0.5s cubic-bezier(.4,0,.2,1);
}

.header-content {
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  width: 100%;
  padding: 0 2rem;
  min-height: var(--header-height);
}

header h1 {
  margin: 0;
  font-weight: 600;
  font-size: 1.6rem;
}
header h2 {
  margin: 0;
  font-weight: 400;
  font-size: 1rem;
  color: #888;
}

main {
  flex: 1;
  width: 90%;
  margin: 2rem auto 1.2rem auto;
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 2rem 1.5rem;
  animation: fadeInUp 0.7s cubic-bezier(.4,0,.2,1);
  transition: background var(--transition);
}

nav {
  margin: 1.2rem 0;
}
nav ul, nav ul.menu {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}
nav ul li, nav ul.menu li {
  margin: 0;
  padding: 0;
}
nav ul li a, nav ul.menu li a {
  display: block;
  background: #f3f6fa;
  color: var(--primary-dark);
  /* padding now scalable via CSS variables */
  padding: var(--dropdown-padding-vertical) var(--dropdown-padding-horizontal);
  border-radius: var(--radius);
  text-align: left;
  font-weight: 500;
  text-decoration: none;
  border: 1px solid var(--border);
  transition: background var(--transition), color var(--transition), border var(--transition);
  font-size: 1rem;
}
nav ul li a:hover, nav ul.menu li a:hover,
nav ul li a:focus, nav ul.menu li a:focus {
  background: var(--primary);
  color: var(--text-light);
  border: 1.5px solid var(--primary-dark);
}

.button2, .button3, button,
input[type="button"], input[type="submit"] {
  background: var(--primary);
  color: var(--text-light);
  border: none;
  border-radius: var(--radius);
  padding: 0.7rem 1.3rem;
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: background var(--transition), color var(--transition);
}
.button2:hover, .button3:hover, button:hover,
input[type="button"]:hover, input[type="submit"]:hover {
  background: var(--primary-dark);
  color: var(--text-light);
}

.dropdown-btn {
  background: #f3f6fa;
  color: var(--primary-dark);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.9rem 1.2rem;
  font-size: 1.05rem;
  font-weight: 500;
  margin: 0.7rem 0 0.3rem 0;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  transition: background var(--transition), border var(--transition);
}
.dropdown-btn .arrow {
  margin-left: 0.5rem;
  transition: transform var(--transition);
}
.dropdown-btn:hover, .dropdown-btn:focus {
  background: var(--primary);
  color: var(--text-light);
  border: 1.5px solid var(--primary-dark);
}
.dropdown-btn.rotate .arrow {
  transform: rotate(180deg);
}

/*
.dropdown-content {
  height: 0;
  overflow: hidden;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-top: 0.5rem;
}
*/

.dropdown-content {
  /* 折叠时彻底隐藏 */
  height: 0;
  overflow: hidden;
  background: var(--card);
  margin: 0;            /* 去掉上下 margin */
  border: none;         /* 去掉边框 */
  transition: none;     /* 关闭默认 transition，完全交给 JS 控制 */
}

.dropdown-btn.open + .dropdown-content {
  margin-top: 0.2rem;       /* 只在打开时才留出间距 */
  border: 1px solid var(--border);
  border-radius: var(--radius);
}

/* 下拉面板 内边距 可调 */
.dropdown-content section,
.dropdown-content nav {
  // padding: var(--dropdown-padding-vertical) var(--dropdown-padding-horizontal);
  padding: 0.2rem 0.3rem;
}

.card {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.3rem;
  margin: 1.2rem 0;
  transition: box-shadow var(--transition), background var(--transition);
}
.card:hover {
  box-shadow: 0 4px 16px rgba(37,99,235,0.10);
}

.warning {
  display: flex;
  align-items: center;
  background: #f8d7da;
  color: #a94442;
  padding: 0.8rem 1.1rem;
  border-radius: var(--radius);
  font-weight: 500;
  margin: 0.8rem 0;
  border: 1px solid #f5c6cb;
}
.warning .icon {
  margin-right: 0.7rem;
  font-size: 1.1em;
  font-weight: bold;
}

.divider {
  border: none;
  height: 1px;
  background: var(--border);
  margin: 2rem 0 1.2rem 0;
  border-radius: var(--radius);
  opacity: 0.8;
}

section {
  margin-bottom: 1.2rem;
}

/*
footer {
  background: #fff;
  color: #888;
  text-align: center;
  padding: 1.3rem 0 1rem 0;
  border-radius: var(--radius) var(--radius) 0 0;
  box-shadow: 0 -2px 8px rgba(30,64,175,0.04);
  font-size: 0.98rem;
  margin-top: 2rem;
  border-top: 1px solid var(--border);
}
*/

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(24px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes fadeInDown {
  from { opacity: 0; transform: translateY(-24px); }
  to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 900px) {
  main, .header-content {
    max-width: 98vw;
    padding: 1rem;
  }
}
@media (max-width: 600px) {
  header, main, .card, .dropdown-content {
    padding: 0.7rem !important;
  }
  .header-content {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.4rem;
  }
  nav ul li a, nav ul.menu li a {
    font-size: 0.98rem;
  }
}

::-webkit-scrollbar {
  width: 8px;
  background: var(--bg);
}
::-webkit-scrollbar-thumb {
  background: var(--primary);
  border-radius: var(--radius);
}