:root{
  --asset:#2563eb;     /* 資産：青 */
  --liability:#dc2626; /* 負債：赤 */
  --equity:#16a34a;    /* 純資産：緑 */
  --revenue:#ea580c;   /* 収益：橙 */
  --expense:#7c3aed;   /* 費用：紫 */
  --ink:#1e293b;
  --bg:#f1f5f9;
  --card:#ffffff;
}
*{box-sizing:border-box;margin:0;padding:0}
body{
  font-family:"Segoe UI","Hiragino Kaku Gothic ProN","Yu Gothic",system-ui,sans-serif;
  color:var(--ink);background:var(--bg);line-height:1.8;-webkit-font-smoothing:antialiased;
}
/* ===== 上部ナビ ===== */
.topnav{position:sticky;top:0;z-index:50;background:rgba(255,255,255,.85);backdrop-filter:blur(8px);
  border-bottom:1px solid #e2e8f0;display:flex;align-items:center;gap:14px;padding:10px 16px}
.topnav a{color:#4f46e5;text-decoration:none;font-weight:700;font-size:14px}
.topnav a:hover{text-decoration:underline}
.topnav .home{display:flex;align-items:center;gap:6px}
.topnav .spacer{flex:1}
.topnav .prog{font-size:13px;color:#64748b}
/* ===== ヘッダー ===== */
header{background:linear-gradient(135deg,#4f46e5 0%,#7c3aed 50%,#db2777 100%);
  color:#fff;padding:48px 20px 56px;text-align:center;position:relative;overflow:hidden}
header::after{content:"";position:absolute;inset:0;
  background:radial-gradient(circle at 20% 30%,rgba(255,255,255,.15),transparent 40%),
             radial-gradient(circle at 80% 70%,rgba(255,255,255,.12),transparent 40%)}
header .badge{display:inline-block;background:rgba(255,255,255,.2);border:1px solid rgba(255,255,255,.4);
  padding:4px 16px;border-radius:999px;font-size:14px;margin-bottom:14px;backdrop-filter:blur(4px)}
header h1{font-size:clamp(26px,5vw,40px);font-weight:800;letter-spacing:.02em;position:relative}
header p{margin-top:10px;opacity:.95;font-size:16px;position:relative}
/* ===== レイアウト ===== */
main{max-width:840px;margin:0 auto;padding:0 16px 60px}
section{background:var(--card);border-radius:20px;padding:28px 24px;margin-top:28px;
  box-shadow:0 4px 24px rgba(15,23,42,.06);border:1px solid #e2e8f0}
.sec-num{display:inline-flex;align-items:center;justify-content:center;width:34px;height:34px;border-radius:10px;
  background:linear-gradient(135deg,#6366f1,#a855f7);color:#fff;font-weight:800;margin-right:10px;font-size:16px;flex:0 0 auto}
h2{display:flex;align-items:center;font-size:22px;margin-bottom:18px;font-weight:800}
h3{font-size:17px;margin:22px 0 10px;color:#334155;border-left:5px solid #a855f7;padding-left:10px}
p.lead{font-size:16px;margin-bottom:8px}
.muted{color:#64748b;font-size:14px}
/* ===== 吹き出し・ポイント ===== */
.point{background:#fef9c3;border:1px solid #fde047;border-radius:14px;padding:14px 16px;margin:16px 0;display:flex;gap:10px;align-items:flex-start}
.point .ic{font-size:22px;flex:0 0 auto}
.tip{background:#dbeafe;border:1px solid #93c5fd;border-radius:14px;padding:14px 16px;margin:16px 0}
.warn{background:#fee2e2;border:1px solid #fca5a5;border-radius:14px;padding:14px 16px;margin:16px 0}
/* ===== 5要素カード ===== */
.elements{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:14px;margin:18px 0}
.el{border-radius:16px;padding:16px;color:#fff;position:relative;overflow:hidden;min-height:120px;
  display:flex;flex-direction:column;justify-content:space-between;box-shadow:0 6px 18px rgba(0,0,0,.12)}
.el .nm{font-size:18px;font-weight:800}
.el .pos{font-size:13px;background:rgba(255,255,255,.25);padding:2px 10px;border-radius:999px;display:inline-block;margin-top:6px}
.el .ex{font-size:12.5px;opacity:.95;margin-top:8px;line-height:1.6}
.el.asset{background:linear-gradient(135deg,#3b82f6,#1d4ed8)}
.el.liability{background:linear-gradient(135deg,#ef4444,#b91c1c)}
.el.equity{background:linear-gradient(135deg,#22c55e,#15803d)}
.el.revenue{background:linear-gradient(135deg,#f97316,#c2410c)}
.el.expense{background:linear-gradient(135deg,#8b5cf6,#6d28d9)}
/* ===== B/S・P/L 箱 ===== */
.statements{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin:18px 0}
@media(max-width:560px){.statements{grid-template-columns:1fr}}
.box{border:2px solid #cbd5e1;border-radius:14px;overflow:hidden}
.box .ttl{background:#334155;color:#fff;text-align:center;padding:8px;font-weight:700;font-size:15px}
.box .row{display:flex;min-height:64px}
.box .half{flex:1;padding:12px;font-size:14px}
.box .l{border-right:2px dashed #cbd5e1}
.tag{display:inline-block;color:#fff;border-radius:6px;padding:1px 8px;font-size:12.5px;font-weight:700;margin:2px 0}
.t-asset{background:var(--asset)} .t-liability{background:var(--liability)}
.t-equity{background:var(--equity)} .t-revenue{background:var(--revenue)} .t-expense{background:var(--expense)}
/* ===== ホームポジション ===== */
.home{display:grid;grid-template-columns:1fr 1fr;gap:0;border:3px solid #334155;border-radius:14px;overflow:hidden;margin:18px 0}
.home .side{padding:16px}
.home .left{background:#eff6ff;border-right:3px solid #334155}
.home .right{background:#fef2f2}
.home .side h4{font-size:15px;margin-bottom:8px;display:flex;align-items:center;gap:6px}
.home .side ul{list-style:none;font-size:14px}
.home .side li{padding:4px 0;display:flex;align-items:center;gap:6px}
.home .side li::before{content:"●";font-size:9px}
.arrow-up{color:#16a34a} .arrow-down{color:#94a3b8}
/* ===== 仕訳T字 ===== */
table.mini{width:100%;border-collapse:collapse;margin:14px 0;font-size:14px}
table.mini th,table.mini td{border:1px solid #e2e8f0;padding:8px 10px;text-align:center;vertical-align:top}
table.mini th{background:#f1f5f9}
.journal{width:100%;border-collapse:collapse;margin:14px 0;font-size:15px;border:2px solid #334155}
.journal th{background:#334155;color:#fff;padding:8px}
.journal td{border:1px solid #cbd5e1;padding:10px 12px;width:50%;vertical-align:top}
.journal td.dr{background:#eff6ff} .journal td.cr{background:#fef2f2}
/* ===== クイズ ===== */
.quiz{background:linear-gradient(135deg,#faf5ff,#fdf2f8);border:2px dashed #d8b4fe;border-radius:16px;padding:20px;margin-top:20px}
.quiz .q{font-weight:700;font-size:16px;margin-bottom:12px}
.opts{display:grid;gap:10px}
.opt{background:#fff;border:2px solid #e2e8f0;border-radius:12px;padding:12px 14px;cursor:pointer;font-size:15px;transition:.15s;text-align:left}
.opt:hover{border-color:#a855f7;transform:translateY(-1px)}
.opt.correct{background:#dcfce7;border-color:#22c55e}
.opt.wrong{background:#fee2e2;border-color:#ef4444}
.feedback{margin-top:12px;font-weight:700;display:none}
/* ===== アコーディオン ===== */
details{border:1px solid #e2e8f0;border-radius:12px;margin:10px 0;overflow:hidden}
summary{cursor:pointer;padding:12px 16px;background:#f8fafc;font-weight:700;list-style:none}
summary::-webkit-details-marker{display:none}
summary::before{content:"▶ ";color:#a855f7;font-size:12px}
details[open] summary::before{content:"▼ "}
details .body{padding:12px 16px}
.chip{display:inline-block;background:#ede9fe;color:#6d28d9;border-radius:8px;padding:2px 8px;font-size:12.5px;font-weight:700}
/* ===== 章送り ===== */
.chapnav{display:flex;justify-content:space-between;gap:12px;margin-top:28px}
.chapnav a{flex:1;text-decoration:none;border-radius:14px;padding:16px;font-weight:700;color:#fff;
  background:linear-gradient(135deg,#6366f1,#a855f7);box-shadow:0 6px 18px rgba(99,102,241,.3)}
.chapnav a.prev{background:linear-gradient(135deg,#64748b,#475569);text-align:left}
.chapnav a.next{text-align:right}
.chapnav a.disabled{visibility:hidden}
.chapnav small{display:block;font-weight:500;opacity:.85;font-size:12px}
/* ===== index 目次 ===== */
.hero-cta{margin-top:18px}
.toc{display:grid;grid-template-columns:repeat(auto-fit,minmax(230px,1fr));gap:16px;margin-top:8px}
.toc a{text-decoration:none;color:inherit;background:var(--card);border:1px solid #e2e8f0;border-radius:18px;
  padding:20px;display:block;transition:.15s;box-shadow:0 4px 16px rgba(15,23,42,.05)}
.toc a:hover{transform:translateY(-3px);box-shadow:0 10px 28px rgba(99,102,241,.18);border-color:#c4b5fd}
.toc .ch{font-size:13px;font-weight:800;color:#a855f7}
.toc .ti{font-size:18px;font-weight:800;margin:6px 0}
.toc .de{font-size:13.5px;color:#64748b}
.toc .ic{font-size:30px}
.badge-soft{display:inline-block;background:#ede9fe;color:#6d28d9;border-radius:999px;padding:3px 12px;font-size:12.5px;font-weight:700}
/* ===== フッター ===== */
footer{text-align:center;color:#94a3b8;font-size:13px;padding:30px 16px}