/* =====================
   1. 色彩变量（Color）
   ===================== */
:root {
  --primary: #2563eb;      /* 主色：蓝 */
  --primary-dark: #1d4ed8; /* 主色深 */
  --accent: #f59e0b;       /* 强调色：橙 */
  --text: #1f2937;         /* 正文色 */
  --text-light: #6b7280;   /* 次要文字 */
  --bg: #f9fafb;           /* 背景色 */
  --white: #ffffff;
  --border: #e5e7eb;
  --radius: 12px;
  --shadow: 0 4px 20px rgba(0, 0, 0, .06);
}

/* =====================
   2. 基础重置
   ===================== */
* { margin: 0; padding: 0; box-sizing: border-box; }

/* =====================
   3. 字体（Font）
   ===================== */
body {
  font-family: -apple-system, "PingFang SC", "Microsoft YaHei", "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.7;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

h1 { font-size: 2.2rem; font-weight: 700; letter-spacing: -.5px; }
h2 { font-size: 1.5rem; font-weight: 600; margin-bottom: 24px; }
h3 { font-size: 1.1rem; font-weight: 600; margin-bottom: 8px; }
p  { color: var(--text-light); }

a { color: var(--primary); text-decoration: none; transition: .2s; }
a:hover { color: var(--primary-dark); }

.container { max-width: 900px; margin: 0 auto; padding: 0 24px; }

/* =====================
   4. 导航栏（布局 + 交互）
   ===================== */
nav {
  position: sticky;
  top: 0;
  background: rgba(255, 255, 255, .9);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
  z-index: 100;
}
nav .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 64px;
}
nav .logo {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--primary);
}
nav ul { display: flex; gap: 28px; list-style: none; }
nav ul a {
  color: var(--text-light);
  font-size: .95rem;
  position: relative;
}
nav ul a:hover,
nav ul a.active { color: var(--primary); }
nav ul a::after {
  content: "";
  position: absolute;
  left: 0; bottom: -6px;
  width: 0; height: 2px;
  background: var(--primary);
  transition: width .25s;
}
nav ul a:hover::after,
nav ul a.active::after { width: 100%; }

/* =====================
   5. 首屏 Hero
   ===================== */
header {
  padding: 80px 0 60px;
  background: linear-gradient(135deg, #eff6ff, #ffffff);
  border-bottom: 1px solid var(--border);
}
.hero {
  display: flex;
  align-items: center;
  gap: 40px;
  flex-wrap: wrap;
}
.avatar {
  width: 130px; height: 130px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid var(--white);
  box-shadow: var(--shadow);
}
.hero-text h1 { margin-bottom: 8px; }
.hero-text .role {
  color: var(--primary);
  font-size: 1.05rem;
  margin-bottom: 12px;
}
.hero-text .desc { max-width: 480px; margin-bottom: 20px; }

.btn-group { display: flex; gap: 12px; flex-wrap: wrap; }
.btn {
  display: inline-block;
  padding: 10px 24px;
  border-radius: 999px;
  font-size: .95rem;
  cursor: pointer;
  border: none;
  transition: .25s;
}
.btn-primary {
  background: var(--primary);
  color: var(--white);
}
.btn-primary:hover {
  background: var(--primary-dark);
  color: var(--white);
  transform: translateY(-2px);
  box-shadow: 0 6px 16px rgba(37, 99, 235, .3);
}
.btn-outline {
  background: transparent;
  color: var(--primary);
  border: 1px solid var(--primary);
}
.btn-outline:hover {
  background: var(--primary);
  color: var(--white);
}

/* =====================
   6. 区块通用
   ===================== */
section { padding: 56px 0; }
section h2 {
  display: flex;
  align-items: center;
  gap: 10px;
}
section h2::before {
  content: "";
  width: 4px; height: 22px;
  background: var(--primary);
  border-radius: 2px;
}

/* =====================
   7. 技能标签
   ===================== */
.tags { display: flex; flex-wrap: wrap; gap: 10px; }
.tags span {
  background: var(--white);
  border: 1px solid var(--border);
  color: var(--text-light);
  padding: 6px 16px;
  border-radius: 999px;
  font-size: .9rem;
  transition: .2s;
}
.tags span:hover {
  color: var(--primary);
  border-color: var(--primary);
  transform: translateY(-2px);
}

/* =====================
   8. 项目卡片
   ===================== */
.cards { display: grid; gap: 18px; }
.card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  transition: .25s;
}
.card:hover {
  transform: translateY(-4px);
  border-color: var(--primary);
  box-shadow: var(--shadow);
}
.card p { margin-bottom: 12px; }
.card .links { display: flex; gap: 16px; font-size: .9rem; }

/* =====================
   9. 时间线
   ===================== */
.timeline { list-style: none; }
.timeline li {
  border-left: 2px solid var(--border);
  padding: 0 0 28px 24px;
  position: relative;
}
.timeline li:last-child { padding-bottom: 0; }
.timeline li::before {
  content: "";
  position: absolute;
  left: -7px; top: 8px;
  width: 12px; height: 12px;
  background: var(--primary);
  border-radius: 50%;
  box-shadow: 0 0 0 4px rgba(37, 99, 235, .15);
}
.timeline .date {
  font-size: .85rem;
  color: var(--primary);
  margin-bottom: 4px;
}
.timeline strong { display: block; margin-bottom: 4px; color: var(--text); }
.timeline p { font-size: .92rem; }

/* =====================
   10. 留言板（人机交互）
   ===================== */
.message-box {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: var(--shadow);
}
.form-group { margin-bottom: 18px; }
.form-group label {
  display: block;
  font-size: .92rem;
  margin-bottom: 6px;
  color: var(--text);
}
.form-group input,
.form-group textarea {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: .95rem;
  font-family: inherit;
  color: var(--text);
  background: var(--bg);
  transition: .2s;
}
.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--primary);
  background: var(--white);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, .1);
}
.form-group textarea { resize: vertical; min-height: 110px; }

.tip {
  font-size: .85rem;
  color: var(--text-light);
  margin-top: 12px;
}

/* 留言列表（预留展示区） */
.message-list { margin-top: 36px; }
.message-item {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
  margin-bottom: 14px;
  animation: fadeIn .4s ease;
}
.message-item .meta {
  display: flex;
  justify-content: space-between;
  font-size: .85rem;
  color: var(--text-light);
  margin-bottom: 8px;
}
.message-item .meta strong { color: var(--primary); }
.message-item p { color: var(--text); }

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* =====================
   11. 页脚
   ===================== */
footer {
  text-align: center;
  padding: 36px 0;
  color: var(--text-light);
  font-size: .85rem;
  border-top: 1px solid var(--border);
  margin-top: 40px;
}

/* =====================
   12. 响应式（人机交互 - 移动端）
   ===================== */
@media (max-width: 640px) {
  h1 { font-size: 1.7rem; }
  nav ul { gap: 16px; }
  nav ul a { font-size: .85rem; }
  .hero { flex-direction: column; text-align: center; }
  .hero-text .desc { margin-left: auto; margin-right: auto; }
  .btn-group { justify-content: center; }
  header { padding: 50px 0 40px; }
  section { padding: 40px 0; }
  .message-box { padding: 20px; }
}