/* ===== Reset & Base ===== */
*{margin:0;padding:0;box-sizing:border-box}
:root{
--primary:#0D47A1;--primary-light:#1565C0;--primary-dark:#0A3570;
--accent:#29B6F6;--accent-light:#4FC3F7;--accent-dark:#039BE5;
--bg:#F0F4F8;--surface:#FFFFFF;--text:#1A202C;--text-muted:#718096;
--border:#E2E8F0;--shadow:0 2px 8px rgba(0,0,0,.08);--radius:12px;
--font:'Noto Sans JP',sans-serif;
}
html{scroll-behavior:smooth;font-size:16px}
body{font-family:var(--font);background:var(--bg);color:var(--text);line-height:1.7;min-height:100vh}
img{max-width:100%;height:auto;border-radius:var(--radius)}
a{color:var(--primary);text-decoration:none}
a:hover{color:var(--accent)}
ul,ol{padding-left:1.5rem}
strong{font-weight:700}

/* ===== Navbar ===== */
.navbar{display:flex;align-items:center;justify-content:space-between;padding:.75rem 2rem;background:var(--primary);position:sticky;top:0;z-index:100;box-shadow:var(--shadow)}
.navbar .logo{font-size:1.25rem;font-weight:700;color:#fff;text-decoration:none}
.navbar .logo span{color:var(--accent-light)}
.nav-links{display:flex;list-style:none;gap:.25rem;flex-wrap:wrap}
.nav-links a{display:block;padding:.5rem 1rem;color:rgba(255,255,255,.85);border-radius:8px;font-size:.9rem;font-weight:500;transition:all .2s}
.nav-links a:hover,.nav-links a.active{background:rgba(255,255,255,.15);color:#fff}
.nav-toggle{display:none;background:none;border:none;color:#fff;font-size:1.5rem;cursor:pointer}

/* ===== Hero ===== */
.hero{background:linear-gradient(135deg,var(--primary) 0%,var(--primary-dark) 60%,#062F6B 100%);color:#fff;padding:4rem 2rem;text-align:center;position:relative;overflow:hidden}
.hero::before{content:'';position:absolute;inset:0;background:url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.03'%3E%3Ccircle cx='30' cy='30' r='2'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");pointer-events:none}
.hero h1{font-size:2.2rem;font-weight:800;margin-bottom:.75rem;position:relative}
.hero p{font-size:1.1rem;opacity:.9;position:relative;max-width:600px;margin:0 auto}
.hero .btn{display:inline-block;margin-top:1.5rem;padding:.75rem 1.75rem;background:var(--accent);color:#fff;border-radius:50px;font-weight:600;transition:all .2s}
.hero .btn:hover{background:var(--accent-light);transform:translateY(-2px);box-shadow:0 4px 12px rgba(41,182,246,.4)}

/* ===== Container ===== */
.container{max-width:1100px;margin:0 auto;padding:2rem}

/* ===== Cards Grid ===== */
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:1.5rem}
.card{background:var(--surface);border-radius:var(--radius);padding:1.5rem;box-shadow:var(--shadow);transition:all .25s;border:1px solid var(--border);display:block;text-decoration:none;color:inherit}
.card:hover{transform:translateY(-4px);box-shadow:0 8px 24px rgba(0,0,0,.12);border-color:var(--accent)}
.card-icon{font-size:2rem;margin-bottom:.75rem}
.card h3{font-size:1.1rem;font-weight:700;color:var(--primary);margin-bottom:.5rem}
.card p{font-size:.9rem;color:var(--text-muted);line-height:1.5}

/* ===== Article Page ===== */
.article-page{max-width:760px;margin:0 auto;padding:2rem;background:var(--surface);border-radius:var(--radius);box-shadow:var(--shadow)}
.article-page h1{font-size:1.75rem;color:var(--primary);margin-bottom:.5rem;line-height:1.3}
.article-page .meta{color:var(--text-muted);font-size:.9rem;margin-bottom:1.5rem;padding-bottom:1rem;border-bottom:1px solid var(--border)}
.article-page h2{font-size:1.3rem;color:var(--primary-dark);margin:1.75rem 0 .75rem;padding-bottom:.5rem;border-bottom:2px solid var(--accent-light)}
.article-page h3{font-size:1.1rem;color:var(--primary);margin:1.25rem 0 .5rem}
.article-page p{margin-bottom:1rem;font-size:1rem;line-height:1.8}
.article-page ul,.article-page ol{margin-bottom:1rem}
.article-page li{margin-bottom:.4rem}
.article-page img{margin:1.5rem 0;border-radius:var(--radius);box-shadow:var(--shadow)}
.article-page .formula-box{background:linear-gradient(135deg,#E3F2FD,#BBDEFB);border-left:4px solid var(--primary);padding:1rem 1.25rem;border-radius:0 var(--radius) var(--radius) 0;margin:1.25rem 0;font-weight:600;color:var(--primary-dark)}
.article-page .tip-box{background:#E8F5E9;border-left:4px solid #43A047;padding:1rem 1.25rem;border-radius:0 var(--radius) var(--radius) 0;margin:1.5rem 0;color:#2E7D32;font-size:.95rem}
.article-page a{color:var(--primary);text-decoration:underline;text-underline-offset:3px}
.article-page a:hover{color:var(--accent)}

/* ===== Breadcrumb ===== */
.breadcrumb{background:var(--surface);padding:.75rem 2rem;font-size:.9rem;color:var(--text-muted);border-bottom:1px solid var(--border)}
.breadcrumb a{color:var(--primary)}
.breadcrumb a:hover{text-decoration:underline}

/* ===== Footer ===== */
.footer{background:var(--primary-dark);color:rgba(255,255,255,.8);padding:2.5rem 2rem;text-align:center;margin-top:3rem}
.footer-inner{max-width:1100px;margin:0 auto}
.footer-links{display:flex;justify-content:center;gap:1.5rem;flex-wrap:wrap;margin-bottom:1rem}
.footer-links a{color:rgba(255,255,255,.7);font-size:.9rem}
.footer-links a:hover{color:#fff}
.footer p{font-size:.85rem;opacity:.6}

/* ===== Utility ===== */
.btn-primary{display:inline-block;padding:.65rem 1.5rem;background:var(--primary);color:#fff;border-radius:var(--radius);font-weight:600;font-size:.95rem;transition:all .2s;border:none;cursor:pointer}
.btn-primary:hover{background:var(--primary-light);color:#fff;transform:translateY(-1px);box-shadow:0 4px 12px rgba(13,71,161,.3)}
.text-center{text-align:center}

/* ===== 404 ===== */
.error-page{text-align:center;padding:6rem 2rem}
.error-page h1{font-size:6rem;color:var(--primary);margin-bottom:1rem}
.error-page h2{font-size:1.5rem;color:var(--text-muted);margin-bottom:2rem}

/* ===== Form ===== */
.form-group{margin-bottom:1.25rem}
.form-group label{display:block;font-weight:600;margin-bottom:.4rem;color:var(--primary)}
.form-group input,.form-group textarea,.form-group select{width:100%;padding:.65rem 1rem;border:1px solid var(--border);border-radius:8px;font-size:1rem;font-family:var(--font);background:var(--surface)}
.form-group input:focus,.form-group textarea:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px rgba(41,182,246,.15)}

/* ===== Media Query ===== */
@media(max-width:768px){
.navbar{padding:.65rem 1rem;flex-wrap:wrap}
.nav-links{width:100%;justify-content:center;margin-top:.5rem}
.hero{padding:2.5rem 1rem}
.hero h1{font-size:1.6rem}
.container{padding:1rem}
.grid{grid-template-columns:1fr}
.article-page{padding:1.25rem}
.article-page h1{font-size:1.4rem}
.article-page h2{font-size:1.15rem}
}