@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500&family=Noto+Sans+JP:wght@300;400;500&display=swap');

:root {
  /* Colors */
  --bg-dark: #f0f4f8; /* Soft slate/blue-gray for depth instead of pure white */
  --bg-panel: #ffffff; /* pure white cards */
  --bg-overlay: rgba(255, 255, 255, 0.95);
  
  --text-main: #1e293b; /* Dark slate */
  --text-muted: #64748b;
  --text-dark: #475569;
  
  --accent-cyan: #0284c7; /* Elegant muted blue */
  --accent-cyan-glow: rgba(2, 132, 199, 0.1);
  --accent-blue: #0ea5e9;
  
  --border-color: rgba(0, 0, 0, 0.05); /* very subtle border */
  --border-highlight: rgba(2, 132, 199, 0.2);
  --shadow-soft: 0 4px 20px rgba(0, 0, 0, 0.03);
  --shadow-hover: 0 10px 30px rgba(0, 0, 0, 0.08);

  /* Typography */
  --font-en: 'Inter', sans-serif;
  --font-jp: 'Noto Sans JP', sans-serif;
  
  --font-weight-light: 300;
  --font-weight-regular: 400;
  --font-weight-medium: 500;

  /* Layout */
  --max-width: 1200px;
  --header-height: 80px;

  /* Transitions */
  --trans-fast: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --trans-base: 0.5s cubic-bezier(0.4, 0, 0.2, 1);
  --trans-slow: 0.8s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Reset & Base */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-family: var(--font-en), var(--font-jp);
  background-color: var(--bg-dark);
  color: var(--text-main);
  line-height: 1.8;
  scroll-behavior: smooth;
  font-size: 15px; /* Slightly smaller base for elegance */
  font-weight: var(--font-weight-light); /* Thin elegant feel */
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  position: relative;
  overflow-x: hidden;
}

/* Subtle background element */
body::before {
  content: "";
  position: fixed;
  top: 0; left: 0; width: 100vw; height: 100vh;
  background: radial-gradient(circle at 100% 0%, var(--accent-cyan-glow) 0%, transparent 60%);
  z-index: -1;
  pointer-events: none;
}

body::after {
  content: "";
  position: fixed;
  bottom: 0; left: 0; width: 100vw; height: 50vh;
  background: radial-gradient(circle at 0% 100%, rgba(2, 132, 199, 0.05) 0%, transparent 60%);
  z-index: -1;
  pointer-events: none;
}

ul { list-style: none; }

a {
  color: var(--text-main);
  text-decoration: none;
  transition: color var(--trans-fast);
}

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

main {
  flex-grow: 1;
  padding-top: var(--header-height);
}

.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 2rem;
}

/* Typography elements */
h1, h2, h3, h4 {
  font-weight: var(--font-weight-regular);
  line-height: 1.3;
  letter-spacing: 0.05em;
  color: var(--text-main);
}

.section-title {
  font-size: 2.2rem;
  margin-bottom: 3rem;
  position: relative;
  display: inline-block;
  font-weight: var(--font-weight-light);
  letter-spacing: 0.1em;
}

/* Subtle underline instead of heavy border */
.section-title::after {
  content: '';
  position: absolute;
  bottom: -15px;
  left: 50%;
  transform: translateX(-50%);
  width: 40px;
  height: 1px;
  background: var(--text-muted);
}

/* Header */
.site-header {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--header-height);
  background: transparent;
  backdrop-filter: blur(5px);
  -webkit-backdrop-filter: blur(5px);
  border-bottom: 1px solid transparent;
  z-index: 1000;
  display: flex;
  align-items: center;
  transition: all var(--trans-base);
}

.site-header.scrolled {
  background: rgba(255, 255, 255, 0.95);
  border-bottom: 1px solid var(--border-color);
  box-shadow: var(--shadow-soft);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
}

.header-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  width: 100%;
}

.logo-container {
  display: flex;
  align-items: center;
}

.logo-img {
  height: 55px;
  width: auto;
}

.main-nav {
  display: flex;
  gap: 2.5rem;
  align-items: center;
}

.nav-links {
  display: flex;
  gap: 2.5rem;
}

.nav-item {
  position: relative;
  font-size: 0.9rem;
  font-weight: var(--font-weight-regular);
  letter-spacing: 0.05em;
  color: var(--text-dark);
}

.nav-item::after {
  content: '';
  position: absolute;
  bottom: -6px;
  left: 50%;
  transform: translateX(-50%);
  width: 0;
  height: 1px;
  background: var(--accent-cyan);
  transition: width var(--trans-fast);
}

.nav-item:hover::after,
.nav-item.active::after {
  width: 100%;
}
.nav-item:hover, .nav-item.active {
  color: var(--accent-cyan);
}

.lang-toggle {
  background: transparent;
  color: var(--text-dark);
  border: 1px solid var(--border-color);
  padding: 0.4rem 1rem;
  border-radius: 20px;
  cursor: pointer;
  font-family: var(--font-en);
  font-size: 0.8rem;
  font-weight: var(--font-weight-regular);
  transition: all var(--trans-fast);
}

.lang-toggle:hover {
  border-color: var(--accent-cyan);
  color: var(--accent-cyan);
  background: var(--bg-panel);
}

/* Hamburger Menu (Mobile) */
.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  color: var(--text-main);
  cursor: pointer;
  z-index: 1001;
}

/* Footer */
.site-footer {
  background: #0f172a; /* Dark slate */
  color: #f8fafc;
  padding: 5rem 0 3rem;
  margin-top: 6rem;
}

.footer-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3rem;
}

.footer-logos {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  justify-content: center;
}

.footer-logos a {
  display: inline-flex;
  align-items: center;
  padding: 0 2.5rem;
  border-right: 1px solid rgba(255, 255, 255, 0.15);
}

.footer-logos a:last-child {
  border-right: none;
}

.footer-logos img {
  height: 50px;
  transition: all var(--trans-fast);
}

.footer-logos img:hover {
  transform: translateY(-3px);
}

.copyright {
  color: #94a3b8;
  font-size: 0.8rem;
  text-align: center;
  letter-spacing: 0.1em;
  font-weight: var(--font-weight-light);
}

/* Utilities */
html[lang="ja"] .en { display: none !important; }
html[lang="en"] .jp { display: none !important; }
.text-center { text-align: center; }

/* Responsive */
@media (max-width: 1100px) {
  .main-nav {
    position: fixed;
    top: 0; right: -100%;
    width: 300px; height: 100vh;
    background: var(--bg-overlay);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    flex-direction: column;
    justify-content: center;
    padding: 3rem;
    transition: right var(--trans-base);
    border-left: 1px solid var(--border-color);
    box-shadow: -10px 0 30px rgba(0,0,0,0.05);
  }

  .main-nav.open {
    right: 0;
  }

  .nav-links {
    flex-direction: column;
    gap: 2.5rem;
    width: 100%;
    text-align: center;
  }

  .nav-item {
    font-size: 1.1rem;
  }

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

@media (max-width: 768px) {
  .footer-inner {
    gap: 2rem;
  }
  .footer-logos {
    flex-wrap: nowrap;
    gap: 0;
  }
  .footer-logos a {
    padding: 0 0.6rem;
  }
  .footer-logos img {
    height: 32px;
  }
  .site-footer {
    padding: 3rem 0 2rem;
  }
}