/* Base Styles and Variables */
:root {
  --color-bg: #0d0d0f;
  --color-bg-secondary: #14151a;
  --color-primary: #42b4fa;
  --color-primary-light: #b6e3ff;
  --color-text: #f2f2f2;
  --color-text-secondary: #c0c0c0;
  --color-border: #333;
  --font-main: 'Inter', sans-serif;
  --spacing-xs: 8px;
  --spacing-sm: 16px;
  --spacing-md: 24px;
  --spacing-lg: 32px;
  --spacing-xl: 48px;
  --border-radius: 8px;
  --transition-speed: 0.3s;
}

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

body {
  font-family: var(--font-main);
  background-color: var(--color-bg);
  background-image: linear-gradient(rgba(13, 13, 15, 0.5), rgba(13, 13, 15, 0.5)), 
    url('../images/boat-grb-bkg.jpg');
  background-size: cover;
  background-position: center;
  background-attachment: fixed;
  color: var(--color-text);
  line-height: 1.6;
  overflow-x: hidden;
  position: relative;
  min-height: 100vh;
}

/* https://www.esa.int/var/esa/storage/images/esa_multimedia/images/2023/03/xmm-newton_captured_dust_rings_from_gamma-ray_burst_221009a/24769343-1-eng-GB/XMM-Newton_captured_dust_rings_from_gamma-ray_burst_221009A_pillars.jpg */
/* ('https://cdn.arstechnica.net/wp-content/uploads/2022/10/gamma1.jpg' */

/* Typography */
h1, h2, h3, h4, h5, h6 {
  line-height: 1.3;
  margin-bottom: var(--spacing-sm);
  font-weight: 600;
}

h1 {
  font-size: 2.5rem;
  font-weight: 600;
}

h2 {
  font-size: 2rem;
  font-weight: 500;
}

h3 {
  font-size: 1.5rem;
  font-weight: 500;
}

p {
  margin-bottom: var(--spacing-sm);
  text-align: justify;
  font-weight: 400;
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: all var(--transition-speed);
}

a:hover {
  color: var(--color-primary-light);
}

/* Background Stars */
.stars {
  display: none;
}

/* Navigation */
.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-sm) var(--spacing-lg);
  background-color: rgba(13, 13, 15, 0.9);
  backdrop-filter: blur(8px);
  position: sticky;
  top: 0;
  z-index: 1000;
  border-bottom: 1px solid var(--color-border);
}

.logo {
  font-size: 1.8rem;
  font-weight: 600;
  color: var(--color-primary);
  cursor: pointer;
}

.nav-links {
  display: flex;
  list-style: none;
}

.nav-links li {
  margin-left: var(--spacing-md);
}

.nav-links a {
  color: var(--color-text);
  font-weight: 400;
  padding: var(--spacing-xs) 0;
  position: relative;
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--color-primary);
  transition: width var(--transition-speed);
}

.nav-links a:hover::after,
.nav-links .active a::after {
  width: 100%;
}

.mobile-menu-btn {
  display: none;
  flex-direction: column;
  justify-content: space-between;
  width: 30px;
  height: 21px;
  cursor: pointer;
}

.mobile-menu-btn span {
  display: block;
  height: 3px;
  width: 100%;
  background-color: var(--color-text);
  border-radius: 3px;
  transition: all 0.3s;
}

/* Main Content Container */
main {
  padding: var(--spacing-lg) var(--spacing-lg);
  max-width: 1200px;
  margin: 0 auto;
  min-height: calc(100vh - 140px);
}

section {
  margin-bottom: var(--spacing-xl);
}

/* Navigation Buttons */
.next-page-btn {
  display: inline-block;
  padding: var(--spacing-sm) var(--spacing-lg);
  background-color: var(--color-primary);
  color: white;
  border: none;
  border-radius: var(--border-radius);
  font-family: var(--font-main);
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-speed);
  text-align: center;
  text-decoration: none;
  margin-top: var(--spacing-lg);
}

.next-page-btn:hover {
  background-color: var(--color-primary-light);
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(190, 85, 4, 0.3);
  color: white;
}

.next-page-container {
  text-align: center;
  margin-top: var(--spacing-xl);
  padding-top: var(--spacing-lg);
  border-top: 1px solid var(--color-border);
}

/* Buttons */
.btn, 
.download-btn,
.submit-btn,
.project-link,
.pub-link {
  display: inline-block;
  padding: var(--spacing-xs) var(--spacing-sm);
  background-color: var(--color-primary);
  color: white;
  border: none;
  border-radius: var(--border-radius);
  font-family: var(--font-main);
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-speed);
  text-align: center;
  text-decoration: none;
}

.btn:hover, 
.download-btn:hover,
.submit-btn:hover,
.project-link:hover,
.pub-link:hover {
  background-color: var(--color-primary-light);
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(190, 85, 4, 0.3);
  color: white;
}

/* Footer */
footer {
  background-color: rgba(13, 13, 15, 0.9);
  padding: var(--spacing-md) 0;
  text-align: center;
  border-top: 1px solid var(--color-border);
}

.footer-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

.footer-content p {
  margin-bottom: var(--spacing-xs);
}

.image-credits {
  font-size: 0.8rem;
  color: #888;
  font-style: italic;
  margin-top: var(--spacing-xs);
}

/* Responsive Design */
@media (max-width: 768px) {
  .navbar {
    padding: var(--spacing-sm);
  }

  .mobile-menu-btn {
    display: flex;
  }

  .nav-links {
    position: fixed;
    top: 60px;
    right: -100%;
    width: 80%;
    height: calc(100vh - 60px);
    flex-direction: column;
    background-color: var(--color-bg-secondary);
    transition: right 0.3s ease;
    padding: var(--spacing-lg) var(--spacing-md);
    z-index: 1000;
  }

  .nav-links.active {
    right: 0;
  }

  .nav-links li {
    margin: var(--spacing-sm) 0;
  }

  main {
    padding: var(--spacing-md) var(--spacing-sm);
  }

  h1 {
    font-size: 2rem;
  }

  h2 {
    font-size: 1.7rem;
  }

  h3 {
    font-size: 1.3rem;
  }
}

/* Utility Classes */
.text-center {
  text-align: center;
}

.mt-1 { margin-top: var(--spacing-xs); }
.mt-2 { margin-top: var(--spacing-sm); }
.mt-3 { margin-top: var(--spacing-md); }
.mt-4 { margin-top: var(--spacing-lg); }

.mb-1 { margin-bottom: var(--spacing-xs); }
.mb-2 { margin-bottom: var(--spacing-sm); }
.mb-3 { margin-bottom: var(--spacing-md); }
.mb-4 { margin-bottom: var(--spacing-lg); }