/* === Variables === */
:root {
    --color-black: #000000;
    --color-white: #ffffff;
    --color-gray: #696969;
    --color-light-gray: #f5f5f5;
    --color-bg: #fafafa;
    --color-accent: #72C6EF;
    --color-accent-dark: #5AB0D9;
    --color-accent-light: rgba(114, 198, 239, 0.1);
    --color-border: #e0e0e0;
    --font-en: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-jp: 'Noto Sans JP', sans-serif;
    --transition: cubic-bezier(0.4, 0, 0.2, 1);
}

/* === Reset === */
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; font-size: 16px; }
body { font-family: var(--font-jp); color: var(--color-black); line-height: 1.8; background-color: var(--color-white); -webkit-font-smoothing: antialiased; }
.container { max-width: 1400px; margin: 0 auto; padding: 0 60px; }
@media (max-width: 768px) { .container { padding: 0 24px; } }

/* === Header === */
header { position: fixed; top: 0; left: 0; right: 0; z-index: 1000; background: var(--color-white); box-shadow: 0 1px 0 var(--color-border); }
header.transparent { background: transparent; box-shadow: none; transition: all 0.4s var(--transition); }
header.scrolled { background: rgba(255,255,255,0.95); backdrop-filter: blur(20px); box-shadow: 0 1px 0 var(--color-border); }
.header-inner { display: flex; justify-content: space-between; align-items: center; height: 80px; max-width: 1400px; margin: 0 auto; padding: 0 60px; }
.logo { display: flex; align-items: center; text-decoration: none; transition: all 0.3s var(--transition); }
.logo:hover { opacity: 0.6; }
.logo img { height: 32px; width: auto; }

/* === Nav === */
nav ul { display: flex; list-style: none; gap: 48px; }
nav a { font-family: var(--font-en); font-size: 13px; font-weight: 500; color: var(--color-black); text-decoration: none; letter-spacing: 0.05em; position: relative; transition: color 0.3s var(--transition); }
nav a::after { content: ''; position: absolute; bottom: -4px; left: 0; width: 0; height: 2px; background: var(--color-accent); transition: width 0.3s var(--transition); }
nav a:hover::after, nav a.active::after { width: 100%; }

/* === Hamburger === */
.hamburger { display: none; width: 32px; height: 32px; flex-direction: column; justify-content: center; align-items: center; gap: 6px; cursor: pointer; z-index: 1001; }
.hamburger span { width: 24px; height: 1.5px; background: var(--color-black); transition: all 0.3s var(--transition); }
.hamburger.active span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.hamburger.active span:nth-child(2) { opacity: 0; }
.hamburger.active span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

/* === Mobile Menu === */
.mobile-menu { position: fixed; top: 0; left: 0; right: 0; bottom: 0; background: var(--color-white); z-index: 999; display: flex; flex-direction: column; justify-content: center; align-items: center; opacity: 0; visibility: hidden; transition: all 0.4s var(--transition); }
.mobile-menu.active { opacity: 1; visibility: visible; }
.mobile-menu ul { list-style: none; text-align: center; }
.mobile-menu li { margin: 24px 0; opacity: 0; transform: translateY(20px); transition: all 0.4s var(--transition); }
.mobile-menu.active li { opacity: 1; transform: translateY(0); }
.mobile-menu.active li:nth-child(1) { transition-delay: 0.1s; }
.mobile-menu.active li:nth-child(2) { transition-delay: 0.15s; }
.mobile-menu.active li:nth-child(3) { transition-delay: 0.2s; }
.mobile-menu.active li:nth-child(4) { transition-delay: 0.25s; }
.mobile-menu.active li:nth-child(5) { transition-delay: 0.3s; }
.mobile-menu.active li:nth-child(6) { transition-delay: 0.35s; }
.mobile-menu a { font-family: var(--font-en); font-size: 28px; font-weight: 500; color: var(--color-black); text-decoration: none; }

/* === Button === */
.btn-outline { display: inline-flex; align-items: center; gap: 12px; font-family: var(--font-en); font-size: 13px; font-weight: 500; letter-spacing: 0.05em; color: var(--color-black); text-decoration: none; padding: 16px 32px; border: 1px solid var(--color-black); transition: all 0.3s var(--transition); }
.btn-outline:hover { background: var(--color-black); color: var(--color-white); }
.btn-outline::before { content: '←'; transition: transform 0.3s var(--transition); }
.btn-outline:hover::before { transform: translateX(-4px); }

/* === Footer === */
footer { background: #0a0a0a; color: var(--color-white); padding: 80px 0 40px; }
.footer-inner { display: flex; justify-content: space-between; align-items: flex-start; margin-bottom: 80px; }
.footer-logo { display: flex; align-items: center; }
.footer-logo img { height: 36px; width: auto; filter: brightness(0) invert(1); }
.footer-nav ul { display: flex; gap: 48px; list-style: none; }
.footer-nav a { font-family: var(--font-en); font-size: 12px; font-weight: 500; color: rgba(255,255,255,0.5); text-decoration: none; letter-spacing: 0.08em; transition: color 0.3s var(--transition); }
.footer-nav a:hover { color: var(--color-accent); }
.footer-bottom { display: flex; justify-content: space-between; align-items: center; padding-top: 40px; border-top: 1px solid rgba(255,255,255,0.1); }
.copyright { font-family: var(--font-en); font-size: 11px; color: rgba(255,255,255,0.3); letter-spacing: 0.05em; }

/* === Fade In === */
.fade-in { opacity: 0; transform: translateY(40px); transition: opacity 0.8s var(--transition), transform 0.8s var(--transition); }
.fade-in.visible { opacity: 1; transform: translateY(0); }

/* === Responsive === */
@media (max-width: 768px) {
    .header-inner { padding: 0 24px; height: 64px; }
    nav ul { display: none; }
    .hamburger { display: flex; }
    .footer-inner { flex-direction: column; gap: 40px; }
    .footer-nav ul { flex-wrap: wrap; gap: 24px; }
    .footer-bottom { flex-direction: column; gap: 16px; text-align: center; }
}