/* 广延科技-物联网平台 */
:root {
  --primary-color: #4361ee;
  --secondary-color: #3f37c9;
  --accent-color: #4895ef;
  --light-color: radial-gradient(circle, #007fff, #0000ff); /* 蓝色背景 */
  --dark-color: #0b80f5;
  --success-color: #4cc9f0;
  --warning-color: #f72585;
}

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

body {
  background-color: #f5f7fa;
  color: var(--dark-color);
  line-height: 1.6;
}

header {
  background: linear-gradient(
    135deg,
    var(--primary-color),
    var(--secondary-color)
  );
  color: white;
  text-align: center;
  padding: 4rem 1rem;
  position: relative;
  overflow: hidden;
}

header::after {
  content: "";
  position: absolute;
  bottom: -50px;
  left: 0;
  right: 0;
  height: 100px;
  background-color: #f5f7fa;
  transform: skewY(-2deg);
  z-index: 1;
}

header h1 {
  font-size: 3rem;
  margin-bottom: 1rem;
  font-weight: 700;
  text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.2);
}

header p {
  font-size: 1.2rem;
  max-width: 800px;
  margin: 0 auto;
  opacity: 0.9;
}

.categories {
  display: flex;
  justify-content: center;
  gap: 2rem;
  padding: 2rem;
  flex-wrap: wrap;
  margin-top: 1rem;
}

.category-card {
  background: white;
  border-radius: 10px;
  padding: 2rem;
  width: 300px;
  text-align: center;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
  transition: transform 0.3s, box-shadow 0.3s;
  cursor: pointer;
}

.category-card:hover {
  transform: translateY(-10px);
  box-shadow: 0 15px 30px rgba(0, 0, 0, 0.15);
}

.category-card h2 {
  color: var(--primary-color);
  margin-bottom: 1rem;
  font-size: 1.8rem;
}

section {
  padding: 4rem 1rem;
  max-width: 1200px;
  margin: 0 auto;
}

section h2 {
  text-align: center;
  font-size: 2.5rem;
  margin-bottom: 3rem;
  color: var(--dark-color);
  position: relative;
}

section h2::after {
  content: "";
  display: block;
  width: 100px;
  height: 4px;
  background: var(--accent-color);
  margin: 1rem auto;
  border-radius: 2px;
}

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

.course {
  background: white;
  border-radius: 10px;
  overflow: hidden;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
  transition: transform 0.3s;
}

.course:hover {
  transform: translateY(-5px);
}

.course-content {
  padding: 1.5rem;
}

.course h3 {
  color: var(--primary-color);
  margin-bottom: 0.5rem;
  font-size: 1.3rem;
}

.course p {
  color: #666;
}

#contact-form {
  max-width: 600px;
  margin: 0 auto;
  background: white;
  padding: 2rem;
  border-radius: 10px;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
}

#contact-form label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 600;
  color: var(--dark-color);
}

#contact-form input,
#contact-form textarea {
  width: 100%;
  padding: 0.8rem;
  margin-bottom: 1.5rem;
  border: 1px solid #ddd;
  border-radius: 5px;
  font-size: 1rem;
  transition: border-color 0.3s;
}

#contact-form input:focus,
#contact-form textarea:focus {
  outline: none;
  border-color: var(--primary-color);
}

#contact-form button {
  background: var(--primary-color);
  color: white;
  border: none;
  padding: 1rem 2rem;
  font-size: 1rem;
  border-radius: 5px;
  cursor: pointer;
  transition: background 0.3s;
  font-weight: 600;
  width: 100%;
}

#contact-form button:hover {
  background: var(--secondary-color);
}

footer {
  background: var(--dark-color);
  color: white;
  text-align: center;
  padding: 2rem;
  margin-top: 3rem;
}

@media (max-width: 768px) {
  header h1 {
    font-size: 2.2rem;
  }

  .course-list {
    grid-template-columns: 1fr;
  }
}