:root {
  --primary-color: #00adb5; /* Màu xanh chủ đạo */
  --secondary-color: #393e46; /* Màu xám đậm */
  --bg-color: #222831; /* Màu nền tối */
  --bg-light: #303841; /* Màu nền sáng hơn chút */
  --text-color: #eeeeee; /* Màu chữ trắng/xám nhạt */
  --text-muted: #b2b2b2; /* Màu chữ mờ */
  --gold: #ffd700; /* Màu vàng cho highlight */
  --transition: all 0.3s ease;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
}

body {
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.6;
}

/* Utilities */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 20px;
}

a {
  text-decoration: none;
  color: inherit;
}
ul {
  list-style: none;
}

/* Navbar */
.navbar {
  position: fixed;
  top: 0;
  width: 100%;
  background: rgba(34, 40, 49, 0.95);
  padding: 15px 0;
  z-index: 1000;
  border-bottom: 1px solid var(--secondary-color);
  backdrop-filter: blur(10px);
}

.navbar .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-size: 1.5rem;
  font-weight: bold;
  color: var(--primary-color);
}

.nav-links {
  display: flex;
  gap: 20px;
}
.nav-links a {
  font-weight: 500;
  transition: var(--transition);
  font-size: 0.95rem;
}
.nav-links a:hover {
  color: var(--primary-color);
}

.menu-toggle {
  display: none;
  font-size: 1.5rem;
  cursor: pointer;
}

.btn-contact {
  border: 1px solid var(--primary-color);
  padding: 5px 15px;
  border-radius: 5px;
  color: var(--primary-color);
}
.btn-contact:hover {
  background: var(--primary-color);
  color: #fff;
}

/* Hero Section */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  text-align: center;
  padding-top: 80px;
  padding-top: 30px;
}

/* Avatar Styling */
.avatar-container {
  margin-top: 50px;
  margin-bottom: 20px;
}

.hero-avatar {
  width: 160px;
  height: 160px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid var(--primary-color);
  box-shadow: 0 0 25px rgba(0, 173, 181, 0.4);
  transition: var(--transition);
}

.hero-avatar:hover {
  transform: scale(1.05);
  box-shadow: 0 0 35px rgba(0, 173, 181, 0.6);
}

.greeting {
  color: var(--primary-color);
  font-size: 1.2rem;
  margin-bottom: 10px;
}

.hero h1 {
  font-size: 3.5rem;
  margin-bottom: 5px;
  letter-spacing: 1px;
}

.hero h2 {
  font-size: 2rem;
  color: var(--text-muted);
  margin-bottom: 20px;
  min-height: 40px;
}

/* Hero Contact Bar */
.hero-contact-bar {
  display: inline-flex;
  justify-content: center;
  gap: 20px;
  flex-wrap: wrap;
  margin-bottom: 30px;
  background: rgba(255, 255, 255, 0.05);
  padding: 10px 25px;
  border-radius: 30px;
}

.contact-item {
  font-size: 0.95rem;
  color: var(--text-color);
  display: flex;
  align-items: center;
  gap: 8px;
  transition: var(--transition);
}
.contact-item:hover {
  color: var(--primary-color);
}

.summary {
  max-width: 700px;
  margin: 0 auto 35px;
  color: var(--text-muted);
  font-size: 1.1rem;
}

/* Button Container (Desktop) */
.hero-btns {
  display: flex;
  justify-content: center;
  gap: 20px; /* Khoảng cách chuẩn cho desktop */
  flex-wrap: wrap;
  margin-top: 20px;
}

.hero-btns .btn {
  display: inline-block;
  padding: 12px 30px;
  margin-bottom: 30px;
  border-radius: 5px;
  font-weight: bold;
  transition: var(--transition);
  min-width: 160px;
}

.btn-primary {
  background: var(--primary-color);
  color: #fff;
  box-shadow: 0 4px 15px rgba(0, 173, 181, 0.3);
}
.btn-primary:hover {
  transform: translateY(-2px);
}

.btn-secondary {
  border: 1px solid var(--text-muted);
  color: var(--text-muted);
}
.btn-secondary:hover {
  border-color: var(--primary-color);
  color: var(--primary-color);
}

/* Sections General */
.section {
  padding: 80px 0;
}
.section-title {
  text-align: center;
  font-size: 2rem;
  margin-bottom: 50px;
  position: relative;
  text-transform: uppercase;
  letter-spacing: 1px;
}
.section-title::after {
  content: "";
  display: block;
  width: 60px;
  height: 3px;
  background: var(--primary-color);
  margin: 15px auto 0;
}

.bg-light {
  background-color: var(--bg-light);
}

/* Skills Grid */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 20px;
}

.skill-card {
  background: var(--secondary-color);
  padding: 25px;
  border-radius: 10px;
  text-align: center;
  transition: var(--transition);
  border-bottom: 3px solid transparent;
}
.skill-card:hover {
  transform: translateY(-5px);
  border-bottom-color: var(--primary-color);
}
.skill-card i {
  font-size: 2.5rem;
  color: var(--primary-color);
  margin-bottom: 15px;
}
.skill-card h3 {
  margin-bottom: 10px;
  color: #fff;
}
.skill-card p {
  font-size: 0.95rem;
  color: var(--text-muted);
}

/* Timeline */
.timeline-item {
  display: flex;
  gap: 30px;
  padding-bottom: 30px;
  border-left: 2px solid var(--primary-color);
  padding-left: 30px;
  margin-left: 20px;
  position: relative;
}
.timeline-item::before {
  content: "";
  position: absolute;
  left: -9px;
  top: 0;
  width: 16px;
  height: 16px;
  background: var(--bg-color);
  border: 2px solid var(--primary-color);
  border-radius: 50%;
}
.timeline-date {
  min-width: 130px;
  font-weight: bold;
  color: var(--primary-color);
}
.timeline-content ul {
  list-style: disc;
  margin-left: 20px;
  margin-top: 10px;
  color: var(--text-muted);
}

/* Projects */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 30px;
}

.project-card {
  background: var(--secondary-color);
  border-radius: 12px;
  padding: 30px;
  transition: var(--transition);
  border: 1px solid transparent;
}
.project-card:hover {
  border-color: var(--primary-color);
  transform: translateY(-5px);
}
.project-role {
  font-size: 0.85rem;
  color: var(--primary-color);
  display: block;
  margin-bottom: 15px;
  font-weight: bold;
}
.tech-stack {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 20px 0;
}
.tech-stack li {
  background: var(--bg-color);
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 0.8rem;
  color: var(--primary-color);
  border: 1px solid rgba(0, 173, 181, 0.2);
}
.project-highlights {
  margin-bottom: 20px;
  font-size: 0.95rem;
  border-left: 3px solid var(--primary-color);
  padding-left: 15px;
  background: rgba(255, 255, 255, 0.02);
  padding: 10px;
  color: var(--text-muted);
}
.link-text {
  font-size: 0.9rem;
  color: #fff;
  font-weight: bold;
  border-bottom: 1px solid var(--primary-color);
  display: inline-block;
}

/* Certificates Section */
.certs-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
}

.cert-item {
  background: var(--bg-light);
  padding: 20px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  gap: 20px;
  border: 1px solid var(--secondary-color);
  transition: var(--transition);
}

.cert-item:hover {
  border-color: var(--primary-color);
  background: var(--secondary-color);
}

.cert-icon {
  font-size: 2rem;
  color: var(--primary-color);
  min-width: 50px;
  text-align: center;
}

.cert-detail h3 {
  font-size: 1rem;
  margin-bottom: 5px;
  color: #fff;
}

.issuer {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-style: italic;
}

/* Highlighted Cert */
.highlight-cert {
  border-color: var(--gold);
  background: rgba(255, 215, 0, 0.05);
}
.highlight-cert .cert-icon {
  color: var(--gold);
}

/* Footer */
#footer {
  background: #1a1d21;
  padding: 60px 0 20px;
  border-top: 1px solid var(--secondary-color);
}

.footer-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 40px;
  margin-bottom: 40px;
}

.footer-col h3 {
  color: var(--primary-color);
  margin-bottom: 20px;
  font-size: 1.2rem;
  border-bottom: 2px solid var(--secondary-color);
  padding-bottom: 10px;
  display: inline-block;
}

.footer-content h4 {
  font-size: 1.1rem;
  margin-bottom: 10px;
  color: #fff;
}
.footer-content p {
  color: var(--text-muted);
  margin-bottom: 5px;
}

.social-links {
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.social-links a {
  color: var(--text-muted);
  transition: var(--transition);
  display: flex;
  align-items: center;
  gap: 10px;
}
.social-links a:hover {
  color: var(--primary-color);
  padding-left: 5px;
}

.footer-contact p {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 12px;
  color: var(--text-muted);
}
.footer-contact i {
  color: var(--primary-color);
  width: 20px;
}

.copyright-bar {
  text-align: center;
  padding-top: 20px;
  border-top: 1px solid var(--secondary-color);
  color: var(--text-muted);
  font-size: 0.9rem;
}

/* ========================================= */
/* MOBILE RESPONSIVE (Tất cả xử lý ở đây)    */
/* ========================================= */
@media (max-width: 768px) {
  .summary {
    max-width: 600px;
  }
  .avatar-container {
    margin-top: 20px;
  }
  /* 1. Xử lý Navbar */
  .nav-links {
    display: none;
  } /* Ẩn menu desktop */
  .menu-toggle {
    display: block;
    color: var(--text-color);
  }

  /* 2. Xử lý Hero Section */
  .hero {
    padding-top: 100px;
  }
  .hero h1 {
    font-size: 2.5rem;
  }
  .hero-contact-bar {
    flex-direction: column;
    gap: 10px;
  }

  /* 3. Xử lý Nút bấm (Sửa lỗi dính nút) */
  .hero-btns {
    flex-direction: column; /* Xếp dọc */
    width: 100%; /* Rộng 100% container */
    padding: 0 40px; /* Lề 2 bên để nút gọn hơn */
    gap: 0; /* Reset gap để dùng margin cho chắc chắn */
    margin-bottom: 20px;
  }

  .hero-btns .btn {
    width: 100%; /* Nút dài full */
    text-align: center;
    display: block; /* Đảm bảo là khối block */
    margin-bottom: 15px; /* Tạo khoảng cách dưới mỗi nút */
  }

  /* Bỏ margin của nút cuối cùng để không bị thừa */
  .hero-btns .btn:last-child {
    margin-bottom: 0;
  }

  /* 4. Xử lý các phần khác */
  .timeline-item {
    flex-direction: column;
    gap: 10px;
  }
  .footer-container {
    text-align: left;
  }

  .section {
    padding: 40px 0;
  }
}

@media (max-width: 575.98px) {
  .hero-avatar {
    width: 120px;
    height: 120px;
  }
  .hero h1 {
    font-size: 2rem;
  }

  .hero h2 {
    font-size: 1.8rem;
  }

  .summary {
    font-size: 1rem;
  }
  .hero-btns {
    margin-bottom: 20px;
  }

  .section-title {
    font-size: 1.8rem;
    margin-bottom: 30px;
  }
}

@media (max-width: 424.98px) {
  .logo {
    font-size: 1.3rem;
  }

  .hero h1 {
    font-size: 1.8rem;
  }

  .hero h2 {
    font-size: 1.6rem;
  }

  .contact-item {
    font-size: 0.9rem;
  }

  .summary {
    font-size: 0.9rem;
  }

  .hero-btns .btn {
    font-size: 0.85rem;
  }

  .section-title {
    font-size: 1.6rem;
  }

  .project-card {
    padding: 20px;
  }

  p {
    font-size: 14px;
  }

  .projects-grid {
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
  }
}