/* Reset và base styles */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    sans-serif;
  line-height: 1.6;
  color: #333;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

/* Header styles */
.header {
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.2);
  padding: 2rem 0;
  margin-top: 20px;
  margin-bottom: 3rem;
  border-radius: 20px;
  border: 1px solid rgba(255, 255, 255, 0.2);
}

.header-content {
  text-align: center;
}

.logo {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  margin-bottom: 1rem;
}

.logo i {
  font-size: 3rem;
  color: #fff;
  background: linear-gradient(45deg, #ff6b6b, #4ecdc4);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.logo h1 {
  font-size: 2.5rem;
  font-weight: 700;
  color: #fff;
  text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

.subtitle {
  font-size: 1.2rem;
  color: rgba(255, 255, 255, 0.9);
  font-weight: 300;
}

/* Main content */
.main-content {
  margin-bottom: 3rem;
}

.intro-section {
  text-align: center;
  margin-bottom: 4rem;
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(10px);
  padding: 3rem 2rem;
  border-radius: 20px;
  border: 1px solid rgba(255, 255, 255, 0.2);
}

.intro-section h2 {
  font-size: 2.5rem;
  color: #fff;
  margin-bottom: 1rem;
  font-weight: 600;
}

.intro-section p {
  font-size: 1.1rem;
  color: rgba(255, 255, 255, 0.9);
  max-width: 600px;
  margin: 0 auto;
}

/* Assignments section */
.assignments-section {
  margin-bottom: 4rem;
}

.assignments-section h3 {
  font-size: 2rem;
  color: #fff;
  text-align: center;
  margin-bottom: 2rem;
  font-weight: 600;
}

.assignments-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
}

.assignment-card {
  background: rgba(255, 255, 255, 0.95);
  border-radius: 20px;
  padding: 2rem;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
  transition: all 0.3s ease;
  border: 1px solid rgba(255, 255, 255, 0.2);
  position: relative;
  overflow: hidden;
}

.assignment-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, #ff6b6b, #4ecdc4, #45b7d1, #96ceb4);
  transform: scaleX(0);
  transition: transform 0.3s ease;
}

.assignment-card:hover::before {
  transform: scaleX(1);
}

.assignment-card:hover {
  transform: translateY(-10px);
  box-shadow: 0 30px 60px rgba(0, 0, 0, 0.15);
}

.card-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1rem;
}

.card-header i {
  font-size: 2rem;
  color: #667eea;
}

.card-header h4 {
  font-size: 1.5rem;
  color: #333;
  font-weight: 600;
}

.assignment-card p {
  color: #666;
  margin-bottom: 1.5rem;
  font-size: 1rem;
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: linear-gradient(45deg, #667eea, #764ba2);
  color: #fff;
  text-decoration: none;
  padding: 0.8rem 1.5rem;
  border-radius: 50px;
  font-weight: 500;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 25px rgba(102, 126, 234, 0.6);
}

.btn-primary i {
  font-size: 0.9rem;
}

/* Skills section */
.skills-section {
  margin-bottom: 4rem;
}

.skills-section h3 {
  font-size: 2rem;
  color: #fff;
  text-align: center;
  margin-bottom: 2rem;
  font-weight: 600;
}

.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 1.5rem;
  max-width: 600px;
  margin: 0 auto;
}

.skill-item {
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: 15px;
  padding: 1.5rem;
  text-align: center;
  transition: all 0.3s ease;
}

.skill-item:hover {
  background: rgba(255, 255, 255, 0.2);
  transform: translateY(-5px);
}

.skill-item i {
  font-size: 2.5rem;
  margin-bottom: 0.5rem;
  display: block;
}

.skill-item:nth-child(1) i {
  color: #e34f26;
}
.skill-item:nth-child(2) i {
  color: #1572b6;
}
.skill-item:nth-child(3) i {
  color: #f7df1e;
}
.skill-item:nth-child(4) i {
  color: #61dafb;
}

.skill-item span {
  color: #fff;
  font-weight: 500;
  font-size: 1rem;
}

.footer {
  text-align: center;
  padding: 2rem 0;
  color: rgba(255, 255, 255, 0.8);
  border-top: 1px solid rgba(255, 255, 255, 0.2);
}

.footer i {
  color: #ff6b6b;
  margin: 0 0.3rem;
}

@media (max-width: 768px) {
  .container {
    padding: 0 15px;
  }

  .logo h1 {
    font-size: 2rem;
  }

  .intro-section h2 {
    font-size: 2rem;
  }

  .assignments-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .assignment-card {
    padding: 1.5rem;
  }

  .skills-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 480px) {
  .logo {
    flex-direction: column;
    gap: 0.5rem;
  }

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

  .intro-section {
    padding: 2rem 1rem;
  }

  .intro-section h2 {
    font-size: 1.8rem;
  }

  .skills-grid {
    grid-template-columns: 1fr;
  }
}

.assignment-card,
.skill-item {
  animation: fadeInUp 0.6s ease forwards;
}

.assignment-card:nth-child(1) {
  animation-delay: 0.1s;
}
.assignment-card:nth-child(2) {
  animation-delay: 0.2s;
}
.assignment-card:nth-child(3) {
  animation-delay: 0.3s;
}

.skill-item:nth-child(1) {
  animation-delay: 0.4s;
}
.skill-item:nth-child(2) {
  animation-delay: 0.5s;
}
.skill-item:nth-child(3) {
  animation-delay: 0.6s;
}
.skill-item:nth-child(4) {
  animation-delay: 0.7s;
}