:root {
  --accent: #06b6d4;
  --bg: #f8fafc;
  --text: #0f172a;
  --muted: #64748b;
  --card: #ffffff;
  font-family: Inter, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  transition: background 0.3s, color 0.3s;
}

header {
  display: flex;
  align-items: center;
  justify-content: space-between; /* logo bên trái, header-right bên phải */
  padding: 16px 24px;
  background: var(--card);
  box-shadow: 0 2px 6px rgba(0,0,0,0.05);
  position: sticky;
  top: 0;
  z-index: 50;
}

/* phần phải (nav + nút) */
.header-right {
  display: flex;
  align-items: center;
  justify-content: flex-between; /* căn các item về cuối */
  gap: 16px; /* khoảng cách giữa các link và nút */
}

header nav a {
  text-decoration: none;
  color: var(--muted);
  font-weight: 500;
  transition: color 0.3s;
}

header nav a:hover { color: var(--accent); }

.logo {
  font-size: 20px;
  font-weight: 700;
  color: var(--accent);
}

.header-right {
  display: flex;
  align-items: center;
  gap: 12px; /* khoảng cách giữa nav và button */
}

/* nav bên trong header-right */
.header-right nav {
  display: flex; /* cho các <a> nằm cạnh nhau */
  gap: 12px;     /* khoảng cách giữa các link */
}

nav a {
  margin-left: 18px;
  text-decoration: none;
  color: var(--muted);
  font-weight: 500;
  transition: color 0.3s;
}

nav a:hover { color: var(--accent); }

.hero {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  padding: 60px 20px 40px;
}

.hero h1 { font-size: 36px; margin: 20px 0 10px; }

.hero p {
  max-width: 600px;    /* giới hạn chiều ngang */
  margin: 0 auto 28px; /* căn giữa */
  color: var(--muted);
  line-height: 1.6;    /* khoảng cách dòng hợp lý */
  text-align: center;  /* căn giữa text */
}

.btn {
  padding: 12px 20px;
  border: none;
  border-radius: 10px;
  font-weight: 600;
  cursor: pointer;
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
  transition: background 0.3s;
}

.btn-primary { background: var(--accent); color: white; }

section {
  padding: 60px 20px;
  max-width: 1100px;
  margin: auto;
}

h2 { text-align: center; margin-bottom: 28px; }

.features {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 18px;
}

.card {
  border-radius: 14px;
  padding: 20px;
  text-align: center;
  box-shadow: 0 4px 16px rgba(0,0,0,0.05);
  transition: transform 0.3s ease, box-shadow 0.3s ease, background 0.3s ease;
  cursor: pointer;

  /* Màu mặc định, sẽ được theme.js override */
  background: var(--card-color, #ffffff);
}

.card:hover,
.card:focus {
  transform: translateY(-6px);
  box-shadow: 0 8px 24px rgba(0,0,0,0.15);

  /* Màu hover, sẽ được theme.js override */
  background: var(--card-hover-color, #f0f0f0);
}


footer {
  text-align: center;
  padding: 24px;
  background: var(--card);
  margin-top: 40px;
  font-size: 14px;
  color: var(--muted);
  transition: background 0.3s, color 0.3s;
}

#lottie { width: 320px; height: 320px; }

.about-text, .contact-text { max-width:700px; margin:auto; text-align:center; color:var(--muted); }

#theme-toggle {
  margin-left: 16px;
  padding: 6px 10px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  background: var(--card);
  color: var(--text);
  font-size: 18px;
  transition: background 0.3s, color 0.3s;
}

#theme-toggle:hover {
  background: var(--accent);
  color: #fff;
}