:root {
  /* Colors - Light Theme */
  --bg-color: #FFFFFF;
  --bg-color-translucent: rgba(255, 255, 255, 0.95);
  --text-color: #1A202C;
  --text-color-muted: #4A5568;
  --accent-color: #0056B3;
  --accent-color-hover: #004494;
  --accent-secondary: #00A3C4;
  --border-color: #E2E8F0;

  /* Gradients */
  --gradient-main: linear-gradient(135deg, #F7FAFC 0%, #FFFFFF 100%);
  --gradient-text: linear-gradient(90deg, #0056B3, #00A3C4);

  /* Typography */
  --font-main: 'Inter', 'Noto Sans JP', sans-serif;
  --h1-size: 3.5rem;
  --h2-size: 2.5rem;
  --h3-size: 1.75rem;
  --body-size: 1rem;

  /* Spacing */
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 2rem;
  --spacing-xl: 4rem;

  /* Container */
  --container-width: 1200px;
}

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

body {
  font-family: var(--font-main);
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.6;
  background-image: radial-gradient(circle at 50% 10%, rgba(0, 86, 179, 0.05) 0%, transparent 40%);
  min-height: 100vh;
}

a {
  color: inherit;
  text-decoration: none;
  transition: color 0.3s ease;
}

a:hover {
  color: var(--accent-secondary);
}

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

/* Container */
.container {
  width: 90%;
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

/* Typography */
h1,
h2,
h3 {
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: var(--spacing-md);
}

h1 {
  font-size: var(--h1-size);
  letter-spacing: -0.02em;
}

h2 {
  font-size: var(--h2-size);
  position: relative;
  display: inline-block;
  margin-bottom: var(--spacing-xl);
}

h2::after {
  content: '';
  position: absolute;
  left: 0;
  bottom: -10px;
  width: 60px;
  height: 4px;
  background: var(--gradient-text);
  border-radius: 2px;
}

p {
  color: var(--text-color-muted);
  margin-bottom: var(--spacing-md);
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 12px 32px;
  background: var(--accent-color);
  color: white;
  border-radius: 50px;
  font-weight: 600;
  letter-spacing: 0.05em;
  transition: all 0.3s ease;
  border: none;
  cursor: pointer;
}

.btn:hover {
  background: var(--accent-color-hover);
  transform: translateY(-2px);
  box-shadow: 0 4px 20px rgba(77, 124, 254, 0.4);
}

.btn-secondary {
  background: transparent;
  border: 1px solid var(--accent-color);
  color: var(--accent-color);
}

.btn-secondary:hover {
  border-color: var(--accent-color);
  background: rgba(77, 124, 254, 0.1);
}

/* Header */
header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  padding: var(--spacing-md) 0;
  background: var(--bg-color-translucent);
  backdrop-filter: blur(10px);
  z-index: 1000;
  border-bottom: 1px solid var(--border-color);
}

.nav-container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  background: var(--gradient-text);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

nav ul {
  display: flex;
  list-style: none;
  gap: var(--spacing-lg);
}

nav a {
  font-size: 0.95rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-color-muted);
}

nav a.active,
nav a:hover {
  color: var(--text-color);
}

/* Section Common */
section {
  padding: 80px 0;
}

/* Footer Improvements */
footer {
  background: #0a111a;
  padding: 80px 0 40px;
  color: #e2e8f0;
  border-top: none;
}

.footer-content {
  display: grid;
  grid-template-columns: 1.5fr repeat(2, 1fr);
  gap: 60px;
  margin-bottom: 60px;
}

.footer-logo {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 1.5rem;
  color: #FFFFFF;
}

.footer-section h3 {
  font-size: 1.1rem;
  color: #FFFFFF;
  margin-bottom: 1.5rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
}

.footer-links {
  list-style: none;
}

.footer-links li {
  margin-bottom: 0.75rem;
}

.footer-links a {
  color: #a0aec0;
  font-size: 0.95rem;
  transition: color 0.3s ease;
}

.footer-links a:hover {
  color: #60d0ff;
}

.footer-bottom {
  padding-top: 30px;
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  display: block;
  text-align: center;
}

.footer-copyright {
  margin-top: 20px;
  font-size: 0.9rem;
  color: #718096;
}

/* Stealth Link */
.stealth-link {
  color: inherit;
  text-decoration: none;
  transition: opacity 0.3s ease;
}

.stealth-link:hover {
  text-decoration: none;
  opacity: 0.8;
}

/* Responsive Behavior for Footer */
@media (max-width: 768px) {
  .footer-copyright .separator {
    display: none;
  }
  .footer-copyright .produced-by {
    display: block;
    margin-top: 5px;
  }
}

/* Back to Top Button */
#back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 50px;
  height: 50px;
  background: var(--accent-color);
  color: white;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transition: all 0.3s ease;
  z-index: 1000;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

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

#back-to-top:hover {
  background: var(--accent-secondary);
  transform: translateY(-5px);
}

@media (max-width: 768px) {
  .footer-content {
    grid-template-columns: 1fr;
    gap: 40px;
  }
  
  .footer-bottom {
    flex-direction: column;
    text-align: center;
  }
}

/* Mobile Menu */
.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  z-index: 1001;
  padding: 10px;
}

.mobile-menu-btn span {
  display: block;
  width: 25px;
  height: 2px;
  background-color: var(--text-color);
  margin: 5px 0;
  transition: all 0.3s ease;
}

.mobile-menu-btn.active span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.mobile-menu-btn.active span:nth-child(2) {
  opacity: 0;
}

.mobile-menu-btn.active span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

@media (max-width: 768px) {
  :root {
    --h1-size: 2.5rem;
    --h2-size: 2rem;
  }

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

  nav {
    position: fixed;
    top: 0;
    right: -100%;
    width: 100%;
    height: 100vh;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(20px);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: right 0.4s ease;
    z-index: 999;
  }

  nav.active {
    right: 0;
  }

  nav ul {
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-xl);
  }

  nav a {
    font-size: 1.5rem;
  }
}

.nobr {
  display: inline-block;
  white-space: nowrap;
}