* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: system-ui, "Segoe UI", Roboto, sans-serif; background: #f4f7fc; color: #0f172a; line-height: 1.55; }
a { color: #2563eb; text-decoration: none; }
a:hover { text-decoration: underline; }
.page-shell { padding: 16px 12px 40px; }
.app-container, .content-container { max-width: 960px; margin: 0 auto; }
.top-nav { max-width: 960px; margin: 0 auto 18px; background: rgba(255,255,255,0.94); border-radius: 24px; box-shadow: 0 8px 24px rgba(15, 23, 42, 0.05); padding: 14px 18px; }
.nav-inner { display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap; }
.brand-link { font-weight: 800; color: #1e3a8a; font-size: 1rem; }
.nav-links { display: flex; gap: 10px; flex-wrap: wrap; }
.nav-links a { color: #334155; padding: 8px 12px; border-radius: 999px; font-weight: 600; }
.nav-links a.active, .nav-links a:hover { background: #dbeafe; color: #1e3a8a; text-decoration: none; }
.header { text-align: center; margin-bottom: 18px; }
.header h1 { font-size: 1.9rem; color: #1e3a8a; }
.header p { margin-top: 8px; color: #475569; max-width: 760px; margin-left: auto; margin-right: auto; }
.badge { font-size: 0.75rem; background: #d9f99d; display: inline-block; padding: 4px 12px; border-radius: 30px; margin-top: 10px; color: #365314; font-weight: 700; }
.card, .section-card { background: white; border-radius: 32px; box-shadow: 0 8px 24px rgba(0,0,0,0.05); padding: 20px 18px; margin-bottom: 22px; }
.section-card h2, .section-card h3, .card h2, .card h3 { color: #1e3a8a; margin-bottom: 12px; }
.section-card p, .section-card li, .card p, .card li { color: #334155; }
.section-card ul, .card ul { padding-left: 20px; }
.section-card li, .card li { margin-bottom: 8px; }
.export-buttons { display: flex; justify-content: flex-end; gap: 12px; margin-bottom: 12px; }
.export-btn { background: #334155; color: white; border: none; padding: 6px 14px; border-radius: 32px; font-size: 0.75rem; cursor: pointer; }
.solver-tabs { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 22px; justify-content: center; }
.tab-btn { background: #eef2ff; border: none; padding: 8px 16px; border-radius: 40px; font-size: 0.8rem; font-weight: 700; color: #1e40af; cursor: pointer; transition: 0.2s; }
.tab-btn.active { background: #2563eb; color: white; box-shadow: 0 6px 12px rgba(37,99,235,0.25); }
.input-group { margin-bottom: 18px; }
.input-field { margin-bottom: 12px; }
label { font-size: 0.78rem; font-weight: 700; color: #334155; display: block; margin-bottom: 6px; }
input, select { width: 100%; padding: 12px 12px; font-size: 0.95rem; border: 1.5px solid #e2e8f0; border-radius: 24px; background: #ffffff; color: #0f172a; }
input:focus, select:focus { border-color: #3b82f6; outline: none; box-shadow: 0 0 0 3px rgba(59,130,246,0.12); }
button.calc-btn { background: #1e3a8a; width: 100%; padding: 14px; border: none; border-radius: 44px; font-size: 1rem; font-weight: 800; color: white; margin-top: 12px; cursor: pointer; }
.result-box { background: #f8fafc; border-radius: 28px; padding: 18px; margin-top: 20px; border-left: 5px solid #3b82f6; display: none; }
.result-value { font-size: 1.45rem; font-weight: 800; color: #0f172a; background: #eef2ff; padding: 12px; border-radius: 24px; margin-bottom: 12px; }
.copy-buttons { display: flex; flex-wrap: wrap; gap: 8px; margin: 8px 0 12px; }
.copy-btn { background: #e2e8f0; border: none; padding: 6px 12px; border-radius: 32px; font-size: 0.72rem; cursor: pointer; }
.explanation { background: #ffffff; border-radius: 24px; padding: 14px; margin: 12px 0; }
.plain-tip { background: #e6f0ff; padding: 12px; border-radius: 20px; margin-bottom: 16px; color: #1e3a8a; font-weight: 600; }
.step-item { margin-bottom: 12px; padding-left: 16px; border-left: 3px solid #2563eb; }
.graph-area { background: #ffffff; border-radius: 24px; padding: 12px; margin: 16px 0; text-align: center; }
canvas { max-width: 100%; height: auto; background: #fff; border-radius: 20px; }
.faq-section { background: #ffffff; border-radius: 32px; padding: 18px; margin-bottom: 20px; box-shadow: 0 8px 24px rgba(0,0,0,0.05); }
.faq-item { margin: 12px 0; border-bottom: 1px solid #e2e8f0; padding-bottom: 8px; }
.intro-grid, .trust-grid, .guide-grid, .faq-grid { display: grid; gap: 18px; }
.intro-grid, .trust-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.guide-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.faq-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.tool-summary { background: #f8fafc; border-radius: 24px; padding: 16px; border: 1px solid #e2e8f0; }
.tool-summary h3 { font-size: 1.05rem; margin-bottom: 8px; }
.tool-summary p { font-size: 0.92rem; }
.guide-card { background: #f8fafc; border-radius: 24px; padding: 18px; border: 1px solid #e2e8f0; }
.guide-card h3 { margin-bottom: 8px; font-size: 1.05rem; }
.guide-card .read-link { display: inline-block; margin-top: 10px; font-weight: 700; }
.policy-page .section-card, .guide-page .section-card { max-width: 900px; margin-left: auto; margin-right: auto; }
.hero-back { display: inline-block; margin-bottom: 18px; color: #2563eb; font-weight: 700; }
footer { text-align: center; margin-top: 32px; font-size: 0.78rem; color: #475569; border-top: 1px solid #e2e8f0; padding-top: 20px; }
footer .footer-links { margin-bottom: 10px; }
footer a { color: #2563eb; margin: 0 6px; }
@media (max-width: 760px) {
    .intro-grid, .trust-grid, .guide-grid, .faq-grid { grid-template-columns: 1fr; }
    .nav-inner { flex-direction: column; align-items: flex-start; }
    .header h1 { font-size: 1.6rem; }
}