:root {
    --primary: #1a5fb4;
    --primary-dark: #14498c;
    --text-main: #1f2937;
    --text-sub: #6b7280;
    --text-mute: #9ca3af;
    --border: #e5e7eb;
    --bg: #f5f7fa;
    --card-bg: #ffffff;
    --success: #16a34a;
    --warning: #d97706;
    --danger: #dc2626;
}

* { box-sizing: border-box; }

body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
    color: var(--text-main);
    background: var(--bg);
    line-height: 1.6;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

.container { max-width: 1100px; margin: 0 auto; padding: 0 16px; }

/* 头部 */
.site-header { background: var(--primary); color: #fff; }
.nav-bar { display: flex; align-items: center; justify-content: space-between; padding: 12px 16px; flex-wrap: wrap; }
.brand { color: #fff; font-size: 20px; font-weight: 700; }
.brand:hover { text-decoration: none; }
.nav-links { display: flex; align-items: center; gap: 16px; flex-wrap: wrap; }
.nav-links a { color: #e0e9f5; }
.nav-links a:hover { color: #fff; text-decoration: none; }
.link-button { background: none; border: none; color: #e0e9f5; cursor: pointer; font-size: 16px; padding: 0; }
.link-button:hover { color: #fff; }

.main-content { padding: 24px 16px 48px; min-height: 60vh; }

/* 首页 hero */
.hero { text-align: center; padding: 60px 20px; background: linear-gradient(135deg, #1a5fb4, #2563eb); color: #fff; border-radius: 12px; margin-bottom: 32px; }
.hero h1 { font-size: 36px; margin: 0 0 12px; }
.hero p { font-size: 16px; opacity: 0.9; }
.hero-actions { margin-top: 24px; display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }

/* 按钮 */
.btn { display: inline-block; padding: 8px 20px; border-radius: 6px; border: 1px solid transparent; cursor: pointer; font-size: 15px; transition: all .15s; }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); text-decoration: none; }
.btn-secondary { background: #fff; color: var(--primary); border-color: var(--primary); }
.btn-secondary:hover { text-decoration: none; }
.btn-outline { border-color: var(--primary); color: var(--primary); background: transparent; }
.btn-outline:hover { background: #eef4fc; text-decoration: none; }
.btn-danger { background: var(--danger); color: #fff; }
.btn-block { width: 100%; }
.btn-sm { padding: 4px 12px; font-size: 13px; }

/* 卡片与区块 */
.card { background: var(--card-bg); border: 1px solid var(--border); border-radius: 10px; padding: 24px; margin-bottom: 20px; }
.section { margin-bottom: 32px; }
.section-title { font-size: 22px; margin: 0 0 16px; }

/* 课程网格 */
.course-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 16px; }
.course-card { background: var(--card-bg); border: 1px solid var(--border); border-radius: 10px; padding: 20px; }
.course-card h3 { margin: 0 0 8px; font-size: 17px; }
.course-card .desc { color: var(--text-sub); font-size: 14px; min-height: 42px; }
.course-card .meta { color: var(--text-mute); font-size: 13px; }
.course-card .price { color: var(--danger); font-weight: 700; font-size: 18px; }

/* 表单 */
.form-group { margin-bottom: 16px; }
.form-group label { display: block; margin-bottom: 6px; font-weight: 500; }
.form-control { width: 100%; padding: 8px 12px; border: 1px solid var(--border); border-radius: 6px; font-size: 15px; }
.form-control:focus { outline: none; border-color: var(--primary); }
.checkbox label { display: flex; align-items: center; gap: 6px; }
.text-danger { color: var(--danger); font-size: 13px; }
.form-row { display: flex; gap: 12px; flex-wrap: wrap; }
.form-row .form-group { flex: 1; min-width: 150px; }

/* 表格 */
.table { width: 100%; border-collapse: collapse; background: var(--card-bg); border: 1px solid var(--border); border-radius: 10px; overflow: hidden; }
.table th, .table td { padding: 10px 14px; text-align: left; border-bottom: 1px solid var(--border); }
.table th { background: #f9fafb; font-weight: 600; }

/* 徽章 */
.badge { display: inline-block; padding: 2px 10px; border-radius: 20px; font-size: 12px; }
.badge-success { background: #dcfce7; color: var(--success); }
.badge-warning { background: #fef3c7; color: var(--warning); }
.badge-gray { background: #f3f4f6; color: var(--text-sub); }

/* 提示 */
.alert { padding: 12px 16px; border-radius: 6px; margin-bottom: 16px; }
.alert-success { background: #dcfce7; color: var(--success); }
.alert-error { background: #fee2e2; color: var(--danger); }

/* 登录/注册卡片 */
.auth-card { max-width: 420px; margin: 40px auto; background: var(--card-bg); border: 1px solid var(--border); border-radius: 10px; padding: 32px; }
.auth-card h1 { margin: 0 0 24px; text-align: center; }
.auth-switch { text-align: center; margin-top: 16px; color: var(--text-sub); }

/* 表单卡片 */
.form-card { max-width: 640px; margin: 20px auto; background: var(--card-bg); border: 1px solid var(--border); border-radius: 10px; padding: 32px; }
.form-card h1 { margin: 0 0 24px; }

/* 页面头 */
.page-head { display: flex; align-items: center; justify-content: space-between; margin-bottom: 20px; flex-wrap: wrap; gap: 12px; }
.page-head h1 { margin: 0; font-size: 24px; }
.filter-tabs { display: flex; gap: 8px; }

/* 课程详情 */
.course-detail .category { color: var(--primary); }
.course-detail .desc { color: var(--text-sub); }
.course-detail .price { color: var(--danger); font-weight: 700; font-size: 24px; }
.chapter-list { list-style: none; padding: 0; }
.chapter-list li { padding: 12px; border-bottom: 1px solid var(--border); display: flex; align-items: center; gap: 12px; }
.chapter-list .sort { background: #eef4fc; color: var(--primary); padding: 2px 10px; border-radius: 4px; font-size: 13px; }
.chapter-list .title { flex: 1; }

/* 个人中心 */
.profile-header { display: flex; align-items: center; gap: 20px; }
.avatar { width: 72px; height: 72px; border-radius: 50%; object-fit: cover; background: #e5e7eb; }
.nickname { font-size: 20px; font-weight: 600; margin: 0; }
.phone { color: var(--text-sub); margin: 0; }

/* 协议/错误页 */
.legal-page h1, .error-page h1 { font-size: 24px; margin-top: 0; }

/* 志愿测算 */
.volunteer-page { max-width: 520px; margin: 20px auto; }
.volunteer-page .sub { color: var(--text-sub); }
.volunteer-form .form-group { margin-bottom: 16px; }

/* 内联表单 */
.inline-form { display: inline; }

.empty { color: var(--text-mute); text-align: center; padding: 40px 0; }

/* 页脚 */
.site-footer { background: #111827; color: #9ca3af; text-align: center; padding: 24px 16px; margin-top: 40px; }
.site-footer a { color: #9ca3af; }