:root {
  --primary: #4f46e5;
  --secondary: #06b6d4;
  --bg-body: #0f172a;
  --bg-card: #1e293b;
  --bg-hover: #334155;
  --text-main: #f8fafc;
  --text-sub: #94a3b8;
  --gradient-text: linear-gradient(135deg, #818cf8 0%, #22d3ee 100%);
  --glass-border: 1px solid rgba(255, 255, 255, 0.1); /* Gom gọn border */
  --radius-xl: 24px;
  --radius-lg: 16px;
  --container: 1200px;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 100px;
}

body {
  background-color: var(--bg-body);
  background-image: radial-gradient(
      at 0% 0%,
      rgba(79, 70, 229, 0.15),
      transparent 50%
    ),
    radial-gradient(at 100% 0%, rgba(6, 182, 212, 0.15), transparent 50%);
  background-attachment: fixed;

  color: var(--text-main);
  font: 400 1rem/1.6 "Inter", sans-serif;
  min-height: 100vh;
}

.container {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 20px 60px;
}

header {
  text-align: center;
  padding: 60px 0 40px;
}

header h1 {
  font: 800 3.5rem "Outfit", sans-serif;
  letter-spacing: -1px;
  margin-bottom: 10px;
  background: var(--gradient-text);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  display: inline-block;
}

.nav-wrapper {
  position: sticky;
  top: 20px;
  z-index: 100;
  display: flex;
  justify-content: center;
  margin-bottom: 50px;
}

.day-menu {
  display: flex;
  gap: 8px;
  padding: 10px;
  background: rgba(30, 41, 59, 0.7);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: var(--glass-border);
  border-radius: 999px;
  box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.3);
  overflow-x: auto;
}
.day-menu::-webkit-scrollbar {
  display: none;
}
.day-menu a {
  padding: 8px 18px;
  white-space: nowrap;
  text-decoration: none;
  color: var(--text-sub);
  font-weight: 600;
  font-size: 0.9rem;
  border-radius: 999px;
  transition: 0.3s;
}

.day-menu a:hover,
.day-menu a:focus {
  color: #fff;
  background: rgba(255, 255, 255, 0.1);
}

.grid-layout {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 30px;
}

.day-card {
  background: var(--bg-card);
  border-radius: var(--radius-xl);
  padding: 24px;
  border: 1px solid rgba(255, 255, 255, 0.05);
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  transition: 0.3s;
  display: flex;
  flex-direction: column;
}

.day-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.3);
  border-color: rgba(79, 70, 229, 0.3);
}

.day-card h2 {
  font: 1.5rem "Outfit", sans-serif;
  margin-bottom: 20px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.day-card h2::before {
  content: "";
  width: 8px;
  height: 8px;
  background: var(--secondary);
  border-radius: 50%;
  box-shadow: 0 0 10px var(--secondary);
}

.day-card ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
  flex-grow: 1;
}

.day-card li {
  background: rgba(255, 255, 255, 0.03);
  border-radius: var(--radius-lg);
  padding: 12px 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  transition: background 0.2s;
}
.day-card li:hover {
  background: var(--bg-hover);
}

.ex-link {
  text-decoration: none;
  color: var(--text-main);
  font-weight: 500;
  font-size: 0.95rem;
  display: flex;
  align-items: center;
  gap: 8px;
}

.src-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-sub);
  text-decoration: none;
  border: 1px solid transparent;
  transition: 0.2s;
}

.src-btn:hover {
  background: var(--bg-body);
  color: #fff;
  border-color: var(--primary);
  transform: scale(1.1);
}

footer {
  text-align: center;
  margin-top: 60px;
  padding-top: 30px;
  border-top: var(--glass-border);
  color: var(--text-sub);
  font-size: 0.9rem;
}

@media (max-width: 768px) {
  header h1 {
    font-size: 2.5rem;
  }
  .grid-layout {
    grid-template-columns: 1fr;
  }
  .nav-wrapper {
    top: 10px;
  }
}
.ex-link i {
  color: var(--primary);
  margin-right: 6px;
  transition: 0.3s;
}

.ex-link:hover i {
  color: #22d3ee;
  transform: scale(1.1);
}