/* Base Styles */
:root {
  /* Colors */
  --primary-color: #1E3A8A;
  --primary-light: #3B82F6;
  --secondary-color: #1E40AF;
  --accent-color: #F59E0B;
  --success-color: #10B981;
  --warning-color: #F97316;
  --error-color: #EF4444;
  --black: #111827;
  --dark-gray: #4B5563;
  --medium-gray: #9CA3AF;
  --light-gray: #E5E7EB;
  --white: #FFFFFF;
  
  /* Typography */
  --font-family: 'Poppins', sans-serif;
  --heading-line-height: 1.2;
  --body-line-height: 1.6;
  
  /* Spacing */
  --spacing-xs: 0.25rem; /* 4px */
  --spacing-sm: 0.5rem;  /* 8px */
  --spacing-md: 1rem;    /* 16px */
  --spacing-lg: 1.5rem;  /* 24px */
  --spacing-xl: 2rem;    /* 32px */
  --spacing-2xl: 3rem;   /* 48px */
  
  /* Borders */
  --border-radius-sm: 0.25rem; /* 4px */
  --border-radius-md: 0.5rem;  /* 8px */
  --border-radius-lg: 1rem;    /* 16px */
  --border-radius-full: 9999px;
  
  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  
  /* Transitions */
  --transition-fast: 0.2s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-family);
  line-height: var(--body-line-height);
  color: var(--black);
  overflow-x: hidden;
  background-color: var(--white);
}

a {
  text-decoration: none;
  color: inherit;
  transition: var(--transition-normal);
}

ul {
  list-style: none;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

button, 
input, 
textarea, 
select {
  font-family: inherit;
  font-size: inherit;
  border: none;
  outline: none;
}

/* Container */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

/* Section styles */
section {
  padding: var(--spacing-2xl) 0;
  position: relative;
  overflow: hidden;
}

.section-header {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
}

.section-title {
  font-size: 2.5rem;
  margin-bottom: var(--spacing-sm);
  font-weight: 600;
  color: var(--black);
  position: relative;
  display: inline-block;
}

.section-title span {
  color: var(--primary-color);
}

.section-title::after {
  content: '';
  display: block;
  width: 80px;
  height: 4px;
  background: var(--accent-color);
  margin: var(--spacing-sm) auto 0;
  border-radius: var(--border-radius-full);
}

.section-subtitle {
  font-size: 1.1rem;
  color: var(--dark-gray);
  max-width: 600px;
  margin: 0 auto;
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 0.8rem 1.8rem;
  border-radius: var(--border-radius-md);
  font-weight: 500;
  text-align: center;
  cursor: pointer;
  transition: var(--transition-normal);
  text-transform: capitalize;
  box-shadow: var(--shadow-md);
}

.btn-primary {
  background-color: var(--primary-color);
  color: var(--white);
  border: 2px solid var(--primary-color);
}

.btn-primary:hover {
  background-color: transparent;
  color: var(--primary-color);
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
}

.btn-secondary {
  background-color: transparent;
  color: var(--primary-color);
  border: 2px solid var(--primary-color);
}

.btn-secondary:hover {
  background-color: var(--primary-color);
  color: var(--white);
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
}

.btn-course {
  background-color: var(--primary-color);
  color: var(--white);
  width: 100%;
  padding: 0.8rem 0;
  border-radius: var(--border-radius-md);
  transition: var(--transition-normal);
}

.btn-course:hover {
  background-color: var(--secondary-color);
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
}

.btn-submit {
  background-color: var(--primary-color);
  color: var(--white);
  width: 100%;
  padding: 1rem;
  border-radius: var(--border-radius-md);
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition-normal);
  margin-top: var(--spacing-md);
}

.btn-submit:hover {
  background-color: var(--secondary-color);
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
}

/* Back to top button */
.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  background-color: var(--primary-color);
  color: var(--white);
  width: 40px;
  height: 40px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 99;
  opacity: 0;
  visibility: hidden;
  transition: var(--transition-normal);
  box-shadow: var(--shadow-lg);
}

.back-to-top.active {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  background-color: var(--secondary-color);
  transform: translateY(-3px);
}

/* Responsive design */
@media (max-width: 992px) {
  html {
    font-size: 15px;
  }
  .section-title {
    font-size: 2.2rem;
  }
}

@media (max-width: 768px) {
  html {
    font-size: 14px;
  }
  section {
    padding: var(--spacing-xl) 0;
  }
  .section-header {
    margin-bottom: var(--spacing-xl);
  }
  .section-title {
    font-size: 2rem;
  }
}

@media (max-width: 576px) {
  .section-title {
    font-size: 1.8rem;
  }
  .container {
    padding: 0 var(--spacing-sm);
  }
}